Polychromasia on a Blood Smear: What Slight, 1+ and Present Mean

Sample type: Whole Blood

Other names: polychromasia, polychromatophilia, polychromatophils, polychromatophilic, polychromatic cells, polychromasia present, slight polychromasia, polychromasia slight, mild polychromasia, moderate polychromasia, marked polychromasia, polychromasia 1+, polychromasia 2+, polychromasia 3+, rbc polychromasia

Written September 11, 2026

Updated September 11, 2026

By Healthmatters Editorial Team

Peer-reviewed sources

Normal

No immature red cells were recorded in enough number to grade on this film. A healthy blood film can still contain a few of them — the reference literature notes that a normal subject's blood may contain few visible polychromatophilic cells even at around 1% reticulocytes, because the routine stain renders only the youngest of them. Nothing here needs following up on its own.

Slight

Immature red cells were visible on the film, at the low end of what the reporting laboratory records. Slight and 1+ are that laboratory's own categories: the ICSH scheme defines no "few" or 1+ tier for polychromasia, beginning instead at 2+ for 5 to 20% of red cells, so a local grade carries no percentage that can be looked up. Immature cells reach the blood when replacement is running high — after bleeding, while a deficiency is being corrected, at altitude, in pregnancy, or where red cells are being destroyed — and also when a marrow that is not working harder releases them early. Read it beside hemoglobin, and ask whether a reticulocyte count was run; that is the quantitative companion to this grade.

Moderate (2+)

On the international grading scheme this is 5 to 20% of red cells appearing as immature cells — the standard's lower defined grade — where that is the scheme the reporting laboratory used. A finding of that size is worth reading against hemoglobin and a reticulocyte count together, because what matters is why the cells are there and whether your hemoglobin shows anemia, rather than the grade itself.

Marked (3+)

On the international grading scheme this is more than 20% of red cells appearing as immature cells, the standard's upper grade, where that is the scheme the reporting laboratory used. It belongs with the rest of the blood count, a reticulocyte count and the clinical history; the grade records how many immature cells were seen, not why they are there and not how serious the underlying situation is.

At a Glance

Polychromasia is not a disease. It describes how your red cells looked under a microscope, and Cleveland Clinic states it plainly: "Polychromasia is a description, not a diagnosis."

What it describes is that some of your red cells are immature. New red cells still carry leftover genetic material from the marrow, which takes up stain differently, so they look bluish-grey next to the pink of a mature cell. The word means "many colors" on the slide.

Immature cells can accompany increased red cell replacement — after bleeding, or where red cells are being destroyed — but the finding alone does not establish that. They also reach the blood when a marrow that is not working harder releases them early, and the reference literature records polychromasia increasing while the reticulocyte count stays normal.

So the reading is narrow: immature red cells were visible. Why is a separate question, with ordinary answers and serious ones.

The wording beside it — present, slight, 1+, moderate, marked — is recorded by eye. Present records that cells were seen, without an amount. Where a grade is given, the international standard for this feature recognizes two levels, and neither is 1+ or slight. A reticulocyte count is the quantitative companion.

What the grade on your report means

The ICSH — the international body that sets standards for laboratory hematology — publishes the reference scheme for grading what a laboratory sees on a blood film. For polychromasia it defines two grades:

Grade	Share of red cells
Few / 1+	Not defined for polychromasia
Moderate / 2+	5–20%
Many / 3+	Over 20%

There is no 1+ tier. Across the whole table of red cell features, one entry has a "few" grade — schistocytes, at under 1% — because those carry weight at low numbers. Polychromasia does not.

So if your report says 1+ or slight, it is using a scheme its own laboratory chose. That is not an error; it is the situation the standard was written to address: "Worldwide, there is a marked variation in blood film evaluation, reporting practices and morphology terminology."

The consequence is worth holding onto. A grade from one laboratory does not convert into a grade from another, and on its own carries no percentage you can look up.

What polychromasia actually is

A red cell leaving the marrow still contains ribosomal RNA. The standard describes the appearance directly: polychromasia refers to "immature red cells that are pinkish blue-grey in appearance due to residual ribosomal RNA."

That RNA is also what a reticulocyte count measures — hematology references put it as "all polychromatophils are reticulocytes."

The reverse does not hold, and that is what matters for reading your own result. On the routine film stain, "only the earliest reticulocytes with the most residual RNA will be 'polychromatophil'." Slightly older ones have lost enough RNA to look like ordinary red cells.

A film therefore shows a fraction of the immature cells present, and the same reference states the consequence: "The correlation between the reticulocyte percentage and the appearance of polychromasia on the peripheral smear is not exact." The two are companions, not readings of one quantity.

It also explains why a small amount is unremarkable: "The normal subject's blood may contain few visible polychromatophilic cells despite, say, 1% reticulocytes."

Where a reticulocyte count is reported, the interval that applies is the one printed beside it — laboratories differ in what they designate a reticulocyte, so "the clinician must know the local normal values and range."

How to read your result

Read these against the grade on your own result.

What your report says	What that establishes	What it leaves open
Nothing about polychromasia	Nothing was recorded	Nothing either way; the feature is not graded on every film
Present, with no grade	Immature cells were seen	How many. `Present` records presence, not amount
Slight, mild, 1+	Cells were seen, at the low end of what that laboratory records	The standard defines no 1+ tier, so this wording is local and carries no percentage
Moderate, 2+	5 to 20% of red cells on the standard's scheme, if that is the one your laboratory used	Why the cells are there
Marked, many, 3+	Over 20% on that scheme, again if it is the one used	The cause, and whether the rest of the count is holding
Any wording, with hemoglobin below your range	Immature cells are present and hemoglobin is low	Whether cells are being lost, destroyed, under-produced, or released early
Any wording, with hemoglobin inside your range	This hemoglobin does not show anemia	The reason stays open — recovery from something past, an ongoing balanced process, or early release from a marrow that is not working harder

No row is a diagnosis.

If you remember only one thing

Ask whether a reticulocyte count was run.

The standard that defines the grading says so itself: "The recommendation is to grade polychromasia and perform a reticulocyte count if necessary." The grade is an impression formed at a microscope; the count is a number you can track between visits. The standard asks for both rather than treating one as a conversion of the other.

Whether it matters and what caused it are read from your hemoglobin, your symptoms and that count rather than from the wording — though not always from those alone. If it stays unexplained, the rest of the blood count and your history decide whether anything further is worth doing.

Two people, same result

Two people are both told their film shows slight polychromasia.

The first donated blood three weeks ago, and their hemoglobin was at the low end afterward. Immature cells are what replacing lost blood looks like, and the finding fits an event they already know about.

The second has felt tired for months and their hemoglobin is below range. Here the same word carries a question rather than an explanation, and the reason has not been established.

Same finding, same wording. What separates them is the hemoglobin beside it and the history behind it.

What this result cannot tell you

The cause. Cleveland Clinic lists hemolytic anemia, severe blood loss, certain cancers, pregnancy, high altitudes, and the period after starting B12, folate or iron supplementation. The grade does not point at any of them.

How severe anything is. It does not measure how low your red cell count is, and a higher grade can accompany a better recovery as easily as a worse problem.

Whether you have anemia. That is read from hemoglobin and hematocrit, and a film can show immature cells while both are normal.

Whether the marrow is working harder at all. Polychromasia "may be increased on the peripheral blood smear even when the reticulocyte count or percentage is normal", which "suggests the premature release of erythroid cells from a marrow that is not hyperactive" — causes including marrow infiltration by tumor or granulomas, or marrow fibrosis. Cleveland Clinic describes the same route for malignancy: certain cancers "can invade your bone marrow and interfere in red blood cell production or force premature blood cells out." It is why the finding is read against the rest of the count, not waved through on a normal hemoglobin.

How many immature cells you have. The routine stain shows only the earliest, so the film undercounts what a reticulocyte count finds — and present records no amount.

Whether anything needs treating. There is no treatment for polychromasia. Cleveland Clinic: "Treatment is based on the cause."

Anything by comparison with someone else's grade. Two laboratories grading one film can print different words.

Common interpretation mistakes

Reading the grade as a severity score. It estimates a proportion of immature cells; the standard defines two levels.

Treating the word as a diagnosis. It describes an appearance; the diagnosis, if there is one, comes from why the cells are there.

Comparing your grade to another laboratory's. The standard exists because reporting practices and terminology vary between them.

Reading a local grade as a percentage. A normal film can show a few immature cells, and slight is a laboratory's own category, not a point on the international scale. The standard's 5 to 20% and over 20% belong to its scheme, and a local slight or 1+ cannot be converted into either without that laboratory's criteria.

Taking present as a small amount. It records that cells were seen, not how many.

Reading "abnormal" beside it as a verdict. A film finding is abnormal when it differs from the plain reference appearance — a statement about the film, not your health.

Looking for a treatment for it. There is nothing to treat; what may need treating is the cause.

Questions your doctor may ask

Have you noticed bleeding — heavy periods, blood in stool, a recent injury or procedure?

Have you donated blood, had surgery, or been at altitude recently?

Are you taking iron, vitamin B12 or folate, and did you start recently?

Have you been unusually short of breath, tired, or lightheaded?

Has your skin or the whites of your eyes looked yellow, or your urine dark?

Do you have an earlier blood count to compare against?

Read together with

Reticulocyte Count — the quantitative companion the grading standard points to; Absolute Reticulocytes gives it as a cell count.

Hemoglobin and Hematocrit — whether the level shows anemia.

MCV — average red cell size. Do not assume a high MCV is explained by immature cells; they are only about 8% larger than mature ones.

RDW — size variation, which rises when a young population joins an older one.

Haptoglobin, LDH and indirect bilirubin — read together when red cell destruction is the question.

Ferritin — iron stores.

Clinical pearls

The result is coded as an ordinal one. LOINC lists it as 10378-8, "Polychromasia [Presence] in Blood by Light microscopy", scale Ord — a graded category rather than a measured quantity.

Across the standard's red cell table, schistocytes are the single feature granted a "few / 1+" grade, at under 1%. Every other feature, polychromasia included, begins at 2+.

The stain decides what is visible: on a new methylene blue preparation reticulocytes are counted directly, while on the routine film stain the RNA "offsets the red of hemoglobin, imparting a purple color" in the youngest cells only.

The film and the count can disagree in both directions: some disorders produce "a disproportionate number of polychromatophilic cells for the percentage of reticulocytes", and polychromasia can be increased where the count is normal. Neither stands in for the other.

Clinical Takeaway

Polychromasia is a morphological description, not a diagnosis: immature red cells carrying residual ribosomal RNA, visible as bluish-grey cells among mature pink ones on a stained film. It is an observation, not a mechanism. Immature cells reach the blood where replacement is running high — blood loss, red cell destruction, altitude, pregnancy, the recovery following treatment of a nutrient deficiency — and also through premature release from a marrow that is not hyperactive, described with marrow infiltration by tumor or granulomas and with marrow fibrosis, where marrow-invading malignancy belongs; polychromasia may be increased even where the reticulocyte count is normal. The grade carries less than readers expect. The ICSH scheme defines two levels only, 2+ at 5 to 20% of red cells and 3+ above 20%, with no "few" or 1+ tier; a report reading slight or 1+ reflects its own laboratory's convention and cannot be assigned an ICSH percentage without that laboratory's criteria, and present records no amount. Because the routine stain renders only the earliest reticulocytes as polychromatophils, the correlation with the reticulocyte percentage is not exact, and a normal subject may show a few polychromatophilic cells. The reticulocyte count is the quantitative companion the standard recommends alongside the grade, read against its own laboratory's interval. Interpretation rests on hemoglobin, the clinical history and that count, which narrow the question without closing it; there is no treatment for the finding, only for its cause.

In one sentence

Polychromasia means immature red cells were visible on your blood film — an observation, not a cause — and the grade beside it is an estimate made by eye rather than a measurement.

Bottom line

Polychromasia on your report describes what your red cells looked like, not what you have. Immature cells were visible; why they were there is a separate question the finding alone does not answer.

If it says slight or 1+, the international grading standard defines neither term for this feature — that wording is the laboratory's own and cannot be turned into a percentage without its criteria. If it says present, no amount was recorded. A healthy film can show a few immature cells.

The finding becomes readable beside your hemoglobin and a reticulocyte count — hemoglobin for whether it shows anemia, the count as the quantitative companion, read against its own lab's interval. Those narrow the question without always settling it; if it stays unexplained, the rest of the count and your history decide what follows.

Take the result to the clinician who ordered it, with your full blood count and any earlier ones. There is no treatment for polychromasia itself: what matters is why the cells are there.

Organize and understand all your lab results

Start organizing — $15/mo →

For Health Professionals Healthmatters Pro Multiple clients’ results in one dashboard. See Pro plans →

Polychromasia

Every lab result you’ve ever had, charted and explained.

Healthmatters is a tracker for your lab results. Upload a report from any lab, any country — every marker charted and explained.

Start with my report →

Frequently Asked Questions

Is slight polychromasia normal?

A blood film from a healthy person can contain a few immature red cells. The reference literature states it directly: "the normal subject's blood may contain few visible polychromatophilic cells despite, say, 1% reticulocytes" — because the routine stain shows only the earliest of them. Slight is the reporting laboratory's own category rather than a point on the international scale: the ICSH scheme defines no "few" or 1+ tier for polychromasia, beginning at 2+ for 5 to 20% of red cells, so a local slight cannot be assigned an ICSH percentage unless that laboratory publishes its criteria. What decides whether it matters is your hemoglobin, your history and, where one has been run, your reticulocyte count.

What does polychromasia 1+ mean?

It means the laboratory that read your film graded the number of immature red cells at the lowest step of the scale it uses. That scale is its own: the ICSH grading recommendations define no 1+ or "few" level for polychromasia, beginning instead at 2+ for 5 to 20% of red cells. Across the standard's entire red cell table, schistocytes are the only feature given a "few / 1+" grade, at under 1%. So a 1+ cannot be converted into an ICSH percentage unless that laboratory publishes the criteria behind its grades, and it cannot be compared with a 1+ from a different laboratory. It tells you immature cells were seen, at the low end of what that laboratory records.

What does it mean when polychromasia is "present"?

It means the person reading the film saw immature red cells and recorded their presence without assigning a level. Immature cells reach circulation where replacement is running high — after bleeding, where red cells are being destroyed, at altitude, in pregnancy, and in the recovery that follows treatment of an iron, B12 or folate deficiency — and also through early release from a marrow that is not working harder, which is where marrow-invading cancers belong. "Present" does not distinguish between those, and does not say how many were seen. Read beside your hemoglobin it becomes more informative, though a normal hemoglobin does not by itself settle why the cells are there.

Is polychromasia serious?

The finding itself is not a condition. Cleveland Clinic states that "polychromasia is a description, not a diagnosis." What it records is that immature red cells were visible, and the reasons range from ordinary to serious: recovery after blood loss, adaptation to altitude, pregnancy, the period after treatment of a nutrient deficiency begins, and destruction of red cells all produce it, as does early release from a marrow that is not working harder — the route Cleveland Clinic describes for marrow-invading cancers. The grade does not rank those. Seriousness is read from your hemoglobin, your symptoms and the cause — and where a reticulocyte count comes back normal and the finding is still unexplained, the rest of the blood count, the film and your history are what decide whether anything further is needed. That is why the result belongs with the clinician who ordered it rather than being interpreted on its own.

What causes polychromasia?

Anything that puts immature red cells into circulation. Cleveland Clinic lists hemolytic anemia, severe blood loss, certain cancers, pregnancy, high altitudes, and the nutrients that raise red cell production — and on those it is specific: polychromasia "may show up in your bloodwork once you start taking vitamins and supplements", so with B12, folate and iron it is the deficiency being treated that is described, not the untreated deficiency. There is also a route that does not involve a busier marrow at all: immature cells can be released early by a marrow that is not hyperactive, described with marrow infiltration by tumor or granulomas and with marrow fibrosis. Cleveland Clinic places cancer on that side too — certain cancers "can invade your bone marrow and interfere in red blood cell production or force premature blood cells out into your bloodstream." The finding does not identify which applies to you; that comes from the rest of the blood count, a reticulocyte count, your history, and where those leave it open, more specific tests.

What is the difference between polychromasia and a reticulocyte count?

They look at overlapping populations by two methods. Polychromasia is an impression formed at the microscope from a stained film and reported as a grade; a reticulocyte count is a measurement, reported as a percentage or an absolute number. Hematology references state that "all polychromatophils are reticulocytes." The reverse is not true, and that is the practical difference: on the routine film stain, "only the earliest reticulocytes with the most residual RNA" appear as polychromatophils, so a film shows fewer immature cells than a reticulocyte method detects. The reference literature is explicit that "the correlation between the reticulocyte percentage and the appearance of polychromasia on the peripheral smear is not exact." The two are companions — the ICSH recommendation is to "grade polychromasia and perform a reticulocyte count if necessary" — rather than one being a conversion of the other.

Does polychromasia need treatment?

There is no treatment for polychromasia, because it is not a condition. Cleveland Clinic's position is that "treatment is based on the cause," and that treatment may not be needed at all where the cause is mild and there are no symptoms. Where something does need addressing — bleeding, destruction of red cells, a nutrient deficiency — it is that which is treated, and the young cells on the film are evidence of the marrow responding rather than something to be corrected. Hemoglobin and a reticulocyte count give quantitative ways to follow recovery — Labcorp lists the reticulocyte count as a way to "evaluate erythropoietic response to antianemic therapy." Whether the film itself is looked at again depends on why it was ordered and what the rest of the blood count shows.

What does moderate or marked polychromasia mean?

These are the two grades the international standard actually defines. On the ICSH scheme, moderate or 2+ means 5 to 20% of red cells appear as immature cells, and marked, many or 3+ means more than 20% — where that is the scheme the reporting laboratory used. Both record a substantial number of immature cells on the film. Neither identifies a cause, and neither measures how low your red cell count is: a large number of immature cells can accompany a good recovery as readily as a serious problem, and can also arise from early release by a marrow that is not working harder. Read with hemoglobin, a reticulocyte count and the clinical history, they say how many immature cells were seen, which is what the grade is there to record.

Clinical Sources & References

All our content is backed by peer-reviewed studies, academic research, and trusted medical sources. We’re committed to accuracy and transparency — see our editorial policy for details.

ICSH recommendations for the standardization of nomenclature and grading of peripheral blood cell morphological features

International Journal of Laboratory Hematology · 2015 View source ↗
What Is Polychromasia?

Cleveland Clinic · 2023 View source ↗
Reticulocytes

Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd edition. Butterworths, Boston · 1990 View source ↗
Polychromatophils versus reticulocytes

eClinPath, Cornell University College of Veterinary Medicine · 2025 View source ↗
Red blood cells: color

eClinPath, Cornell University College of Veterinary Medicine · 2025 View source ↗
Reticulocyte Count, test 005280

Labcorp · 2025 View source ↗
Polychromasia [Presence] in Blood by Light microscopy, LOINC 10378-8

Regenstrief Institute, LOINC · 2025 View source ↗

Article Review Log

Last reviewed September 11, 2026

Originally published September 11, 2026

Reviewed by HealthMatters Editorial Team

Written by Healthmatters Editorial Team

Organize and understand all your lab results

Start organizing — $15/mo →

For Health Professionals Healthmatters Pro Multiple clients’ results in one dashboard. See Pro plans →

Healthmatters Lifetime Plan

Pay $250. Track your health forever

One payment. No renewals. Yours for life.

10,000+ biomarkers explained · trends over time

See other plans →

Secure checkout via Stripe · GDPR & HIPAA

We accept results from any lab

LabCorp Quest Diagnostics Genova Diagnostics DUTCH Test Doctor's Data Vibrant America ZRT Laboratory Cyrex Labs + any other lab

What members are saying

★★★★★ 10,000+ happy members

★★★★★

"Watching my numbers move over the years — instead of forgetting last time's results — completely changed how I manage my health."

Daniel

Member since 2022

★★★★★

"Living across several countries made keeping my lab results organized a real challenge. Healthmatters brought my results from the USA, Spain, and Germany together — 20 years of history, with long-term trends instead of scattered reports."

Ben

Member since 2021 · tracks across countries

★★★★★

"Standard lab ranges are too wide for how I practice — 'normal' isn't optimal. I set my own bands, so a client sees yellow before a marker goes officially out of range. That's the conversation I want to be having."

Dr. Alexandra

Functional medicine · 6 yrs on Pro

Polychromasia on a Blood Smear: What Slight, 1+ and Present Mean

At a Glance

What the grade on your report means

What polychromasia actually is

How to read your result

If you remember only one thing

Two people, same result

What this result cannot tell you

Common interpretation mistakes

Questions your doctor may ask

Read together with

Clinical pearls

Clinical Takeaway

In one sentence

Bottom line

Organize and understand all your lab results

Every lab result you’ve ever had, charted and explained.

Frequently Asked Questions

Related Health Conditions

Pay $250. Track your health forever

What members are saying