What does a progesterone level of 0.1 mean?

A progesterone level of 0.1 ng/mL (0.32 nmol/L) is at the lower end of the follicular phase reference range (0.1–0.9 ng/mL) and is the upper limit of the postmenopausal reference range (0.0–0.1 ng/mL). Whether 0.1 ng/mL is normal depends entirely on when the test was drawn. If drawn in the early follicular phase (days 1–10 of the menstrual cycle) or if the person is postmenopausal, 0.1 ng/mL is within the expected range. If drawn in the mid-luteal phase (around day 21 of a 28-day cycle) as part of an ovulation confirmation test, 0.1 ng/mL would fall far below the reference threshold and would suggest anovulation. Always check the cycle phase against the result.

What does a progesterone level of 0.3 mean?

A progesterone level of 0.3 ng/mL (0.95 nmol/L) is within the normal follicular phase reference range (0.1–0.9 ng/mL) and is a completely normal finding in the pre-ovulation phase of the cycle. If the test was drawn on day 3–10 of the cycle (follicular phase), 0.3 ng/mL indicates normal, expected low progesterone. If drawn as a day 21 ovulation assessment test, 0.3 ng/mL falls well below the range generally associated with ovulation (approximately 3–5 ng/mL / 10–16 nmol/L in many clinical settings) and would suggest ovulation may not have occurred. The key question is always when in the cycle the blood was drawn.

What does a progesterone level of 0.9 mean?

A progesterone level of 0.9 ng/mL (2.86 nmol/L) is at the upper limit of the follicular phase reference range (0.1–0.9 ng/mL). In the follicular phase, 0.9 ng/mL is normal — it may indicate that ovulation is approaching or has recently occurred. It is well below the luteal phase reference range (1.8–23.9 ng/mL) and would be considered low if drawn mid-luteal. In practice, a result of 0.9 ng/mL on a day 21 draw falls below the range generally associated with ovulation (approximately 3–5 ng/mL / 10–16 nmol/L in many clinical settings), suggesting either that ovulation occurred later than expected or did not occur.

How do I convert progesterone from nmol/L to ng/mL?

To convert nmol/L to ng/mL: divide by 3.18. To convert ng/mL to nmol/L: multiply by 3.18. Examples: 5 nmol/L ÷ 3.18 = 1.57 ng/mL; 10 ng/mL × 3.18 = 31.8 nmol/L. US laboratories (LabCorp, Quest) typically report progesterone in ng/mL. UK and most European labs report in nmol/L. The numerical values are very different between the two scales — a normal luteal phase result of 15 ng/mL (US lab) equals approximately 47.7 nmol/L (UK lab). Always check which unit your lab uses before comparing to reference ranges.

What is PROGEST SERPL-MCNC on a lab report?

"PROGEST SERPL-MCNC" is the LOINC display name for a serum or plasma progesterone test. It stands for "Progesterone, Serum or Plasma, Mass Concentration" (MCNC = mass concentration). It is the same test as "progesterone," "serum progesterone," or "P4" — just formatted using the LOINC medical coding system that some laboratory information systems display verbatim. Interpret the result using the standard progesterone reference ranges for your cycle phase.

What is the normal progesterone level on day 21?

In a standard 28-day cycle, a day 21 progesterone test is drawn 7 days after presumed ovulation to confirm that ovulation occurred. A progesterone result above approximately 3–5 ng/mL (10–16 nmol/L), when drawn about 7 days after ovulation, generally supports that ovulation occurred. Laboratories and fertility clinics may use different thresholds, and a single measurement cannot fully assess luteal phase function.

What does it mean if progesterone is high in a non-pregnant woman?

Moderately elevated progesterone in the mid-luteal phase is normal and expected — it confirms that ovulation occurred and the corpus luteum is functioning. If progesterone is markedly elevated outside the luteal phase or far above the luteal reference range, possible explanations include pregnancy, progesterone medication or fertility treatment, normal luteal-phase production, or occasionally an ovarian cyst. Rare endocrine or hormone-secreting tumors are generally considered only when progesterone is persistently unexpected, markedly elevated, and accompanied by other concerning clinical findings.

¿Qué significa un nivel de progesterona de 0.21 o 0.30 ng/mL? (What does a progesterone level of 0.21 or 0.30 ng/mL mean — Spanish?)

Un nivel de progesterona de 0.21 o 0.30 ng/mL está dentro del rango normal para la fase folicular del ciclo menstrual (rango de referencia: 0.1–0.9 ng/mL). Durante la fase folicular (días 1–10 del ciclo), la progesterona es naturalmente baja. Si el análisis se realizó en la fase folicular, estos valores son completamente normales. Sin embargo, si el análisis se realizó alrededor del día 21 del ciclo para evaluar la ovulación, estos valores estarían por debajo del rango generalmente asociado con la ovulación (aproximadamente 3–5 ng/mL o 10–16 nmol/L en muchos entornos clínicos), lo que podría indicar que la ovulación no ocurrió en ese ciclo. La interpretación siempre depende del momento del ciclo en que se extrajo la muestra.

Progesterone Blood Test: What Your Level Means by Cycle Phase, Normal Ranges in ng/mL and nmol/L, and How to Read Your Result

Serum

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Optimal Result: 0.3 - 50.6 nmol/L, or 0.09 - 15.91 ng/mL.

Endocrinology

From Healthmatters.io Team and reviewed by HM Editorial Team

Written on June 26, 2026 | Last updated Updated on June 26, 2026

Lab Results Explained and Tracked

QUICK ANSWER

Progesterone reference ranges change dramatically by menstrual cycle phase. A value of 0.3 ng/mL is normal in the follicular phase but would indicate failure to ovulate if found in the mid-luteal phase.

Cycle phase / status	Normal range (ng/mL)	Normal range (nmol/L)
Follicular phase	0.1–0.9 ng/mL	0.3–2.9 nmol/L
Ovulation phase	0.1–12.0 ng/mL	0.3–38.2 nmol/L
Luteal phase	1.8–23.9 ng/mL	5.7–76.0 nmol/L
Postmenopausal	0.0–0.1 ng/mL	0.0–0.3 nmol/L
Pregnancy — 1st trimester	11.0–44.3 ng/mL	35.0–140.9 nmol/L
Pregnancy — 2nd trimester	25.4–83.3 ng/mL	80.8–265.0 nmol/L
Pregnancy — 3rd trimester	58.7–214.0 ng/mL	186.7–680.5 nmol/L
Males	0.1–0.3 ng/mL	0.3–1.0 nmol/L

Reference ranges based on widely cited laboratory standards; verify against your lab's specific reference interval printed on your report.

The most important rule for interpreting a progesterone result: always know which cycle phase the blood was drawn in.

HOW TO INTERPRET YOUR PROGESTERONE RESULT IN 3 STEPS

Step 1 — Identify your situation:

I am…	Go to…
Currently pregnant	Pregnancy reference ranges (1st / 2nd / 3rd trimester rows above)
Postmenopausal	Postmenopausal range: 0.0–0.1 ng/mL is normal
Male	Male range: 0.1–0.3 ng/mL is normal
Having menstrual cycles	Step 2

Step 2 — Identify your cycle day:

What day of your menstrual cycle was the blood drawn? (Day 1 = first day of your period.)

Day drawn	Most likely phase	Expected progesterone
Days 1–13	Follicular	0.1–0.9 ng/mL (0.3–2.9 nmol/L)
Around day 14	Ovulatory	0.1–12.0 ng/mL (0.3–38.2 nmol/L)
Days 18–26 (or ~7 days before period)	Mid-luteal	1.8–23.9 ng/mL (5.7–76.0 nmol/L)
Days 26–28	Late luteal	Falling toward follicular levels

Step 3 — Compare your result to the correct phase range:

Use the reference range for your specific phase — not an overall "normal" range. A result of 0.3 ng/mL is normal in the follicular phase but would fall well below the mid-luteal range.

WHAT IS PROGESTERONE AND WHAT DOES THE TEST MEASURE?

Progesterone is a steroid hormone produced primarily by the corpus luteum (the structure that forms in the ovary after ovulation) and, during pregnancy, by the placenta. It plays a central role in regulating the menstrual cycle and supporting pregnancy.

The progesterone blood test measures the concentration of progesterone in serum or plasma. It appears on lab reports under several labels:

Label on report	What it means
Progesterone	Standard label
PROGEST SERPL-MCNC	LOINC display name — "Progesterone, Serum or Plasma, Mass Concentration" — same test. Some electronic health records and patient portals display standardized LOINC terminology instead of the common laboratory name. "PROGEST SERPL-MCNC" and "Progesterone" refer to the same laboratory measurement.
P4	Clinical abbreviation for progesterone (P4 = the fourth progestogen in biosynthetic order)
Progesterone Ser QN	"Serum, Quantitative" — same test, different formatting
Progesterone LC/MS	Measured by liquid chromatography–mass spectrometry — more sensitive method, same hormone
Progesterone, Serum	Same test

Why timing is everything: Progesterone levels can increase by well over 100-fold during the menstrual cycle — from near zero in the follicular phase to peaks of 10–30 ng/mL in the mid-luteal phase. A result of 0.3 ng/mL is completely normal if drawn in the follicular phase, but would indicate anovulation (failure to ovulate) if drawn in the mid-luteal phase (day 21 of a 28-day cycle).

WHICH PHASE AM I IN? A QUICK CYCLE TIMELINE

If you are unsure which phase applies to your result, use this guide:

Cycle day*	Phase	What progesterone is doing
Days 1–13	Follicular	Low — ovary producing very little progesterone before ovulation
Around day 14	Ovulatory	Rising sharply — corpus luteum beginning to form
~7 days after ovulation	Mid-luteal (peak)	Peak levels — this is when a day 21 test is ideally drawn
Days before period	Late luteal	Falling — corpus luteum regresses; drop triggers menstruation
Postmenopausal	—	Near zero — no ovulatory cycles

Cycle timing varies. In longer or shorter cycles, phases occur earlier or later. A 35-day cycle ovulates around day 21; a 21-day cycle ovulates around day 7.

PHASE-SPECIFIC REFERENCE RANGES — ng/mL AND nmol/L

The table below covers the most commonly cited reference ranges based on published laboratory data. Your lab's printed reference range is the authoritative guide for your specific result. LabCorp, Quest, and other major US laboratories may differ slightly.

Phase / Status	ng/mL range	nmol/L range	Clinical notes
Follicular phase	0.1–0.9	0.3–2.9	Pre-ovulation baseline; low progesterone is normal
Ovulation phase	0.1–12.0	0.3–38.2	Rises sharply around ovulation; wide range
Mid-luteal phase (Day 21)	1.8–23.9	5.7–76.0	Peak of cycle; confirms ovulation if elevated
Late luteal phase	1.8–23.9 → falling	Falling toward follicular	Falls before menstruation; can cause PMS symptoms
Postmenopausal	0.0–0.1	0.0–0.3	Near-zero after menopause
Pregnancy — 1st trimester	11.0–44.3	35.0–140.9	Supports uterine lining; rising trend expected
Pregnancy — 2nd trimester	25.4–83.3	80.8–265.0	Placenta now primary source
Pregnancy — 3rd trimester	58.7–214.0	186.7–680.5	Continues rising through pregnancy
Males	0.1–0.3	0.3–1.0	Low baseline; produced in adrenal glands and testes

UNIT CONVERSION — nmol/L TO ng/mL

US laboratories (LabCorp, Quest, most hospital labs) report progesterone in ng/mL. UK, European, and many international labs report in nmol/L. These are completely different numerical scales.

Conversion formula:

ng/mL → nmol/L: multiply by 3.18
nmol/L → ng/mL: divide by 3.18

Common conversion table:

ng/mL	nmol/L	Typical phase context
0.05	0.16	Below follicular lower limit
0.1	0.32	Follicular lower limit / postmenopausal upper limit
0.3	0.95	Mid-follicular phase
0.5	1.59	Upper follicular range
0.7	2.23	Upper follicular range
0.9	2.86	Follicular upper limit
1.0	3.18	Just above follicular, just below luteal lower limit
1.8	5.72	Luteal phase lower limit
2.6	8.27	Low-normal luteal
5.0	15.9	Mid-luteal range
9.9	31.5	Mid-luteal range
15.0	47.7	Mid-to-upper luteal
23.9	76.0	Luteal upper limit
43.0	136.7	First trimester
54.0	171.7	First trimester upper / second trimester range
83.0	263.9	Second trimester upper
214.0	680.5	Third trimester upper

If your result is in nmol/L and looks very low (e.g., 0.7 nmol/L, 1.6 nmol/L), it may be in the follicular phase range when converted. 0.7 nmol/L = 0.22 ng/mL — mid-follicular; 1.6 nmol/L = 0.50 ng/mL — upper follicular.

WHY DOES PROGESTERONE CHANGE SO MUCH?

Many users are surprised when they look up reference ranges and find that progesterone can be normal anywhere from 0.05 ng/mL to 214 ng/mL depending on context. Here is the biological reason:

Life stage / cycle event	What is producing progesterone	Result
Before ovulation (follicular phase)	Minimal ovarian production	Near-zero levels (0.1–0.9 ng/mL)
After ovulation (luteal phase)	Corpus luteum — the structure left behind after the follicle releases an egg	Sharp rise to 1.8–23.9 ng/mL peak
If pregnancy occurs	Corpus luteum continues (first ~10 weeks), then placenta takes over	Sustained and rising levels through pregnancy
If no pregnancy	Corpus luteum regresses after ~14 days	Progesterone falls, triggering menstruation
After menopause	Ovaries no longer ovulate; no corpus luteum forms	Returns to near zero

Progesterone levels can increase by well over 100-fold during one menstrual cycle — this is why a value that is completely normal in the follicular phase can indicate anovulation if found in the mid-luteal phase. The number only makes sense when you know when it was drawn.

PROGESTERONE AND ESTRADIOL — INTERPRETING BOTH TOGETHER

HealthMatters users often have both progesterone and estradiol results on the same panel. The combination provides more context than either value alone:

Progesterone	Estradiol	Possible interpretation	Common context
Low	Low	Early follicular phase or ovarian suppression	Normal days 1–5; also seen in menopause or hypothalamic suppression
Low	High	Pre-ovulatory follicle (LH surge approaching) or anovulatory cycle	Estradiol rises before ovulation; if progesterone stays low, ovulation may not have occurred
High	High	Normal luteal phase or early pregnancy	The expected mid-luteal pattern; both hormones elevated after ovulation
High	Low	Progesterone supplementation, or corpus luteum producing progesterone while estradiol has declined	Less common naturally; often reflects exogenous progesterone
Both very low		Postmenopausal or ovarian suppression	Normal after menopause; also seen in hypothalamic amenorrhea

These combinations are general patterns. Interpretation requires knowledge of cycle timing, medications, and clinical context. A reproductive endocrinologist or gynecologist can interpret the full panel in context.

SPECIFIC VALUE LOOKUP — WHAT DOES MY PROGESTERONE LEVEL MEAN?

Important: the interpretation of any progesterone value depends entirely on cycle phase. The same number means very different things depending on when the test was drawn.

Result (ng/mL)	Approximate nmol/L	What it typically means
0.05 / <0.1	0.16 / <0.32	Below most follicular lower limits — may indicate very early cycle, postmenopausal, or anovulatory cycle
0.09	0.29	Low — consistent with early follicular phase or postmenopausal; concerning if mid-luteal
0.1	0.32	Follicular phase lower limit — normal if pre-ovulation; at postmenopausal upper limit
0.2–0.22	0.64–0.70	Within follicular reference range — normal pre-ovulation
0.3	0.95	Normal in follicular phase (range 0.1–0.9); would indicate anovulation in mid-luteal phase
0.5	1.59	Upper follicular range — normal pre-ovulation
0.6	1.91	Upper follicular range — normal pre-ovulation
0.7	2.23	Upper follicular — normal; below luteal lower limit
0.8–0.9	2.54–2.86	At follicular upper limit — normal; ovulation may be imminent or recently occurred
1.0–1.6	3.18–5.09	Above follicular range, below luteal lower limit — transitional; may indicate early post-ovulation
1.8	5.72	Luteal phase lower limit
2.1–2.6	6.68–8.27	Low-normal luteal phase
6.4	20.4	Mid-luteal phase — normal
9.9	31.5	Mid-luteal phase — good luteal response; above common ovulation confirmation threshold
15.9	50.6	Mid-to-upper luteal — normal
23.9	76.0	Luteal upper limit
≥3–5 ng/mL on day 21	≥10–16 nmol/L	Supports ovulation in many clinical settings — thresholds vary by lab and clinician
11.0–44.3	35.0–140.9	First trimester pregnancy range
25.4–83.3	80.8–265.0	Second trimester pregnancy range
58.7–214.0	186.7–680.5	Third trimester pregnancy range

THE DAY 21 PROGESTERONE TEST — WHAT IT IS AND HOW TO INTERPRET IT

The "day 21 progesterone test" is the most commonly ordered clinical use of the serum progesterone test. Here is what it measures and what it means:

What it tests: Ovulation. Progesterone rises sharply after ovulation and peaks approximately 7 days after the LH surge. In a standard 28-day cycle, ovulation occurs around day 14, so the mid-luteal peak falls around day 21 — hence the name.

Interpretation thresholds:

Mid-luteal progesterone result	ng/mL	nmol/L	Interpretation
Low	<3–5	<10–16	Ovulation may not have occurred, but timing should be checked before drawing conclusions
Consistent with ovulation	≥3–5	≥10–16	Supports recent ovulation in many clinical settings
Higher mid-luteal value	≥10	≥32	Often seen after ovulation, but does not independently prove luteal adequacy
Interpret with timing	Any value	Any value	A result is most useful when drawn about 7 days after ovulation, not automatically on cycle day 21

Important limitation: The "day 21" label assumes a 28-day cycle. If your cycle is longer or shorter, the test should be drawn 7 days before expected menstruation — not literally on day 21. A result that looks low may simply reflect that ovulation occurred later than expected.

Can a day 21 progesterone test detect pregnancy? A progesterone level alone cannot diagnose pregnancy. Pregnancy-level progesterone (above 11 ng/mL / 35 nmol/L) on a day 21 draw may suggest early pregnancy, but only an hCG test can confirm. Some users search "can day 21 progesterone show pregnancy" — the answer is: elevated progesterone is consistent with early pregnancy but is not diagnostic.

WHAT DOES "OPTIMAL" PROGESTERONE MEAN?

Several searches ask for "optimal progesterone levels" or "optimal progesterone levels postmenopausal." There is no universally accepted "optimal" progesterone target for wellness or performance outside of specific clinical contexts.

There is no validated wellness target for serum progesterone. Progesterone levels are interpreted relative to cycle phase, pregnancy status, and clinical context — not against a fixed "optimal" range. A result within your lab's phase-appropriate reference range is normal by standard clinical criteria.

Specific contexts where progesterone targets are used:

Fertility treatment / IVF monitoring: Clinicians may target specific luteal phase ranges, but these are individualized and protocol-specific
Hormone replacement therapy (HRT) monitoring: Progesterone levels may be tracked during HRT, but targets are clinical and individualized
Postmenopausal: Normal postmenopausal progesterone is near zero (0.0–0.1 ng/mL). There is no evidence base for a wellness "optimal" postmenopausal progesterone target

If your result is within your lab's phase-appropriate reference range and you have no relevant symptoms, further investigation is generally not indicated from the progesterone result alone.

WHAT DOES LOW PROGESTERONE MEAN?

Low progesterone — below the reference range for the relevant cycle phase — may indicate several things depending on context:

Context	Low progesterone indicates
Mid-luteal phase (day 21 draw)	Possible anovulation (ovulation did not occur) or inadequate corpus luteum function
Early pregnancy	A lower-than-expected value may warrant follow-up with the treating clinician, often alongside serial hCG testing and ultrasound when appropriate — progesterone alone cannot determine pregnancy viability or predict miscarriage with certainty
Follicular phase	A low result in the follicular phase is usually normal — progesterone is expected to be low
Postmenopausal	Very low (0.0–0.1 ng/mL) is normal after menopause
Luteal phase — repeated low results	Repeated low results timed correctly after ovulation may prompt clinical review of ovulation timing, cycle regularity, thyroid function, prolactin, and ovarian function — a single result does not diagnose luteal phase deficiency

Symptoms associated with low progesterone (when clinically significant): Irregular periods, difficulty conceiving, short luteal phase, spotting before menstruation, recurrent early pregnancy loss.

WHAT DOES HIGH PROGESTERONE MEAN?

High progesterone — above the reference range for the cycle phase — may indicate:

Context	High progesterone indicates
Non-pregnant woman	Possible early pregnancy (pregnancy is the most common cause of markedly elevated progesterone), ovarian cyst, congenital adrenal hyperplasia, or — rarely — an ovarian or adrenal tumor
Pregnancy	Rising progesterone through trimesters is normal and expected
On progesterone supplementation	Elevated levels reflect medication; expected finding
Mid-luteal phase	Moderately elevated progesterone (within the reference range) is the expected and desired finding — confirms ovulation

Symptoms sometimes associated with high progesterone: Bloating, breast tenderness, fatigue, mood changes — these overlap with luteal phase symptoms and early pregnancy symptoms.

MEDICATIONS, SUPPLEMENTS, AND TEST INTERPRETATION

Progesterone results can be affected by medications and the testing method used by the laboratory.

Factor	Why it matters
Oral progesterone	Can raise serum progesterone, though measured levels vary by timing of the dose and laboratory method
Vaginal progesterone	May support the uterine lining while producing serum levels that do not fully reflect local uterine exposure
Injectable progesterone	Usually produces higher serum progesterone levels
Hormonal contraception	Suppresses ovulation and typically keeps endogenous progesterone low
Fertility medications	Can substantially change progesterone timing and interpretation
Biotin supplements	High-dose biotin can interfere with some immunoassays — ask the laboratory or clinician whether temporary discontinuation is needed before testing
LC/MS vs immunoassay	Different methods may produce somewhat different results, especially at very low concentrations

If you are using progesterone supplementation, fertility medications, hormonal contraception, or high-dose biotin, include that information when reviewing the result with your clinician.

MOST COMMON PROGESTERONE RESULTS

Result (ng/mL)	Typical context	Interpretation
0.0–0.1	Postmenopausal / early follicular	Normal for phase
0.1–0.9	Follicular phase	Normal — pre-ovulation
0.1–12.0	Ovulation window	Wide range is normal during ovulation transition
<1.8 on day 21	Mid-luteal draw	Below threshold — may suggest anovulation
1.8–23.9	Luteal phase	Normal luteal range
≥3–5 ng/mL (≥10–16 nmol/L) on day 21	Mid-luteal	Supports ovulation; higher values more consistent; thresholds vary by lab
11.0–44.3	First trimester	Normal pregnancy range
25.4–83.3	Second trimester	Normal pregnancy range
58.7–214.0	Third trimester	Normal pregnancy range

COMMON PROGESTERONE INTERPRETATION MISTAKES

These are the most frequent sources of confusion when reading a progesterone result:

Mistake	Why it matters
Comparing a follicular result with luteal ranges	A result of 0.3 ng/mL is normal in the follicular phase but would suggest anovulation if drawn mid-luteal — phase context is everything
Comparing ng/mL to nmol/L without converting	15 ng/mL and 15 nmol/L are not the same — 15 ng/mL converts to 47.7 nmol/L; 15 nmol/L converts to 4.7 ng/mL
Assuming "day 21" applies to every woman	Day 21 is only correct for a 28-day cycle; in a 35-day cycle, the mid-luteal peak is around day 28
Assuming one progesterone level can diagnose infertility	A single result does not diagnose ovulatory dysfunction, luteal phase deficiency, or infertility — timing, repeat testing, and clinical context are required
Forgetting progesterone supplements affect results	Vaginal, oral, and injectable progesterone all affect serum levels — always report supplementation when reviewing results
Comparing to a reference range from a different lab	LabCorp, Quest, and other labs use different assay methods and may have slightly different reference intervals

FAQ about Progesterone (Serum)

What does a progesterone level of 0.1 mean?

A progesterone level of 0.1 ng/mL (0.32 nmol/L) is at the lower end of the follicular phase reference range (0.1–0.9 ng/mL) and is the upper limit of the postmenopausal reference range (0.0–0.1 ng/mL). Whether 0.1 ng/mL is normal depends entirely on when the test was drawn. If drawn in the early follicular phase (days 1–10 of the menstrual cycle) or if the person is postmenopausal, 0.1 ng/mL is within the expected range. If drawn in the mid-luteal phase (around day 21 of a 28-day cycle) as part of an ovulation confirmation test, 0.1 ng/mL would fall far below the reference threshold and would suggest anovulation. Always check the cycle phase against the result.
What does a progesterone level of 0.3 mean?

A progesterone level of 0.3 ng/mL (0.95 nmol/L) is within the normal follicular phase reference range (0.1–0.9 ng/mL) and is a completely normal finding in the pre-ovulation phase of the cycle. If the test was drawn on day 3–10 of the cycle (follicular phase), 0.3 ng/mL indicates normal, expected low progesterone. If drawn as a day 21 ovulation assessment test, 0.3 ng/mL falls well below the range generally associated with ovulation (approximately 3–5 ng/mL / 10–16 nmol/L in many clinical settings) and would suggest ovulation may not have occurred. The key question is always when in the cycle the blood was drawn.
What does a progesterone level of 0.9 mean?

A progesterone level of 0.9 ng/mL (2.86 nmol/L) is at the upper limit of the follicular phase reference range (0.1–0.9 ng/mL). In the follicular phase, 0.9 ng/mL is normal — it may indicate that ovulation is approaching or has recently occurred. It is well below the luteal phase reference range (1.8–23.9 ng/mL) and would be considered low if drawn mid-luteal. In practice, a result of 0.9 ng/mL on a day 21 draw falls below the range generally associated with ovulation (approximately 3–5 ng/mL / 10–16 nmol/L in many clinical settings), suggesting either that ovulation occurred later than expected or did not occur.
How do I convert progesterone from nmol/L to ng/mL?

To convert nmol/L to ng/mL: divide by 3.18. To convert ng/mL to nmol/L: multiply by 3.18. Examples: 5 nmol/L ÷ 3.18 = 1.57 ng/mL; 10 ng/mL × 3.18 = 31.8 nmol/L. US laboratories (LabCorp, Quest) typically report progesterone in ng/mL. UK and most European labs report in nmol/L. The numerical values are very different between the two scales — a normal luteal phase result of 15 ng/mL (US lab) equals approximately 47.7 nmol/L (UK lab). Always check which unit your lab uses before comparing to reference ranges.
What is PROGEST SERPL-MCNC on a lab report?

"PROGEST SERPL-MCNC" is the LOINC display name for a serum or plasma progesterone test. It stands for "Progesterone, Serum or Plasma, Mass Concentration" (MCNC = mass concentration). It is the same test as "progesterone," "serum progesterone," or "P4" — just formatted using the LOINC medical coding system that some laboratory information systems display verbatim. Interpret the result using the standard progesterone reference ranges for your cycle phase.
What is the normal progesterone level on day 21?

In a standard 28-day cycle, a day 21 progesterone test is drawn 7 days after presumed ovulation to confirm that ovulation occurred. A progesterone result above approximately 3–5 ng/mL (10–16 nmol/L), when drawn about 7 days after ovulation, generally supports that ovulation occurred. Laboratories and fertility clinics may use different thresholds, and a single measurement cannot fully assess luteal phase function.
What does it mean if progesterone is high in a non-pregnant woman?

Moderately elevated progesterone in the mid-luteal phase is normal and expected — it confirms that ovulation occurred and the corpus luteum is functioning. If progesterone is markedly elevated outside the luteal phase or far above the luteal reference range, possible explanations include pregnancy, progesterone medication or fertility treatment, normal luteal-phase production, or occasionally an ovarian cyst. Rare endocrine or hormone-secreting tumors are generally considered only when progesterone is persistently unexpected, markedly elevated, and accompanied by other concerning clinical findings.
¿Qué significa un nivel de progesterona de 0.21 o 0.30 ng/mL? (What does a progesterone level of 0.21 or 0.30 ng/mL mean — Spanish?)

Un nivel de progesterona de 0.21 o 0.30 ng/mL está dentro del rango normal para la fase folicular del ciclo menstrual (rango de referencia: 0.1–0.9 ng/mL). Durante la fase folicular (días 1–10 del ciclo), la progesterona es naturalmente baja. Si el análisis se realizó en la fase folicular, estos valores son completamente normales. Sin embargo, si el análisis se realizó alrededor del día 21 del ciclo para evaluar la ovulación, estos valores estarían por debajo del rango generalmente asociado con la ovulación (aproximadamente 3–5 ng/mL o 10–16 nmol/L en muchos entornos clínicos), lo que podría indicar que la ovulación no ocurrió en ese ciclo. La interpretación siempre depende del momento del ciclo en que se extrajo la muestra.

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What does it mean if your Progesterone (Serum) result is too high?

Progesterone above the reference range for the relevant cycle phase has different meanings depending on context. In the mid-luteal phase, a high progesterone result (within or above the 1.8–23.9 ng/mL / 5.7–76.0 nmol/L reference range) is the expected and desired finding — it confirms that ovulation occurred and the corpus luteum is secreting normally. In a non-pregnant woman outside the luteal phase, markedly elevated progesterone warrants review for pregnancy (hCG test), progesterone supplementation, ovarian cyst, or — where progesterone is persistently and markedly elevated with other clinical findings — rarer endocrine causes. In pregnancy, progesterone rises progressively through all three trimesters and a high result in the context of a known pregnancy is normal. Women taking progesterone supplementation (oral, vaginal, or injectable) will have elevated serum levels as expected.

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What does it mean if your Progesterone (Serum) result is too low?

Progesterone below the reference range for the relevant cycle phase may indicate that ovulation did not occur (anovulation) or that the corpus luteum is not producing adequate progesterone. In the follicular phase (days 1–10), low progesterone is normal and expected; the hormone is physiologically low before ovulation. After menopause, very low progesterone (0.0–0.1 ng/mL / 0.0–0.3 nmol/L) is normal. In early pregnancy, a low progesterone result may prompt follow-up, but it must be interpreted alongside gestational age, symptoms, serial hCG measurements, and ultrasound findings. Progesterone alone cannot determine whether a pregnancy is viable. A single low result should be interpreted alongside cycle phase timing, symptoms, and clinical context. Repeated low progesterone results timed correctly after ovulation may prompt a fertility clinician to review ovulation timing, cycle regularity, medications, thyroid function, prolactin, ovarian function, and other possible contributors. A single progesterone result does not diagnose luteal phase deficiency.

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Progesterone Blood Test: What Your Level Means by Cycle Phase, Normal Ranges in ng/mL and nmol/L, and How to Read Your Result

QUICK ANSWER

HOW TO INTERPRET YOUR PROGESTERONE RESULT IN 3 STEPS

WHAT IS PROGESTERONE AND WHAT DOES THE TEST MEASURE?

WHICH PHASE AM I IN? A QUICK CYCLE TIMELINE

PHASE-SPECIFIC REFERENCE RANGES — ng/mL AND nmol/L

UNIT CONVERSION — nmol/L TO ng/mL

WHY DOES PROGESTERONE CHANGE SO MUCH?

PROGESTERONE AND ESTRADIOL — INTERPRETING BOTH TOGETHER

SPECIFIC VALUE LOOKUP — WHAT DOES MY PROGESTERONE LEVEL MEAN?

THE DAY 21 PROGESTERONE TEST — WHAT IT IS AND HOW TO INTERPRET IT

WHAT DOES "OPTIMAL" PROGESTERONE MEAN?

WHAT DOES LOW PROGESTERONE MEAN?

WHAT DOES HIGH PROGESTERONE MEAN?

MEDICATIONS, SUPPLEMENTS, AND TEST INTERPRETATION

MOST COMMON PROGESTERONE RESULTS

COMMON PROGESTERONE INTERPRETATION MISTAKES

FAQ about Progesterone (Serum)

What does a progesterone level of 0.1 mean?

What does a progesterone level of 0.3 mean?

What does a progesterone level of 0.9 mean?

How do I convert progesterone from nmol/L to ng/mL?

What is PROGEST SERPL-MCNC on a lab report?

What is the normal progesterone level on day 21?

What does it mean if progesterone is high in a non-pregnant woman?

¿Qué significa un nivel de progesterona de 0.21 o 0.30 ng/mL? (What does a progesterone level of 0.21 or 0.30 ng/mL mean — Spanish?)

All Your Lab Results. One Simple Dashboard.

What does it mean if your Progesterone (Serum) result is too high?

Related Health Conditions

All Your Lab Results. One Simple Dashboard.

Import, Track, and Share Your Lab Results Easily

Import, Track, and Share Your Lab Results

What does it mean if your Progesterone (Serum) result is too low?

Related Biomarkers

Article Review & Sources

Bring All Your Lab Results Together — In One Place

Gather Your Lab History — and Finally Make Sense of It

Finally, Your Lab Results Organized and Clear

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What's included in a Healthmatters membership

Import Lab Results from Any Source

See Your Health Timeline

Understand What Your Results Mean

Enter Your Lab Reports Yourself — Always Free Enter Your Lab Reports — Always Free

Visualize Your Results

Export Your Complete Lab History in a Single File Export Your Complete Lab History

Comprehensive Data Entry Service for Your Reports Data Entry Service for Your Reports

Securely Share With Anyone You Trust

Let Your Lab Results Tell the Full Story

Once your results are in one place, see the bigger picture — track trends over time, compare data side by side, export your full history, and share securely with anyone you trust.

Bring all your results together to compare, track progress, export your history, and share securely.

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