Lab result explainedBlood count (CBC)Last updated November 11, 2026

Poikilocytosis: what 1+, mild and marked abnormal red cell shapes mean

Poikilocytosis · Peripheral blood smear (reported with the complete blood count) · reported in Semiquantitative grade on the smear (slight/1+ to marked/3+ or 4+); schistocytes and spherocytes may be reported as a percentage of red cells

Poikilocytosis means that an unusual number of your red blood cells have an abnormal shape. A normal red cell is a smooth disc with a dimple in the middle; when a laboratory scientist examining your stained blood smear sees more than a few cells that are oval, pointed, fragmented, spiky, bullseye-shaped or otherwise irregular, the finding is reported as poikilocytosis and graded slight or 1+, moderate or 2+, or marked or 3+ (some labs use 4+). Unlike anisocytosis, which is about size and has a numerical twin in the RDW, poikilocytosis has no automated equivalent, so the smear comment is the whole result.

Mild poikilocytosis is common, non-specific and frequently seen alongside anisocytosis in iron deficiency, B12 or folate deficiency, liver disease and in blood that has sat in the tube for a while before the smear was made. What makes the finding useful is the type of abnormal cell. Pencil cells point to iron deficiency, target cells to liver disease or thalassemia, teardrop cells to a crowded or scarred bone marrow, spherocytes to immune destruction or hereditary spherocytosis, bite cells to oxidative damage, sickle cells to sickle cell disease, and fragments (schistocytes) to red cells being physically torn apart in small vessels, which can be an emergency.

This page explains how poikilocytosis is graded, what each of the main shapes means, which causes are common and which are urgent, and what tests usually follow. If your report simply says 'poikilocytosis 1+' with no shape named and your hemoglobin and other indices are normal, it is very likely unimportant; if it names schistocytes, sickle cells or spherocytes, or you are anemic, the rest of the report and your symptoms decide what happens next.

Poikilocytosis at a glance

What it is: an excess of abnormally shaped red blood cells on a peripheral blood smear, graded slight/1+, moderate/2+ or marked/3+ (some labs 4+).
Normal: a smear with no or only occasional misshapen cells; healthy blood has fewer than about 0.5% fragmented cells.
Mild (1+) poikilocytosis with no shape named and a normal hemoglobin is common and usually unimportant; it often reflects mild iron deficiency or sample handling.
The shape is the message: pencil cells (iron deficiency), target cells (liver disease, thalassemia, hemoglobin C), teardrops (marrow fibrosis or infiltration), spherocytes (immune hemolysis, hereditary spherocytosis), bite cells (G6PD deficiency), sickle cells, schistocytes (mechanical destruction).
Schistocytes above about 1% of red cells together with a low platelet count is an urgent finding (possible TTP, HUS or DIC) that needs same-day hematology review.
Next step: read it with hemoglobin, MCV, RDW, reticulocyte count and platelets, then ferritin, B12, folate, LDH, bilirubin, haptoglobin or hemoglobin electrophoresis as the shapes direct.

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What Poikilocytosis measures

A peripheral smear is a thin film of blood, dried, stained and examined under oil immersion at about 1,000 times magnification in the part of the slide where red cells lie in a single layer without touching. Normal red cells are round, 7 to 8 micrometers across, with a central pale area occupying about a third of the diameter. The scientist estimates what fraction of cells depart from this shape and reports it as a grade, usually naming the dominant shapes when they are specific (for example 'poikilocytosis 2+ with target cells and pencil cells'). Grading schemes differ between laboratories, which is why one report says 'slight' and another '1+'.

Each shape has a name that describes it. Spherocytes are small, dense balls without a central pallor. Elliptocytes and ovalocytes are oval; very thin elongated ones are pencil cells. Target cells (codocytes) have a bullseye of hemoglobin in the middle of the pale area. Teardrop cells (dacrocytes) have a single tapered tail. Schistocytes are fragments with sharp angles, helmet shapes or small triangles. Echinocytes (burr cells) have evenly spaced short projections; acanthocytes (spur cells) have a few irregular, longer spikes. Stomatocytes have a slit-like pale area, bite cells have a semicircular piece missing, and sickle cells are crescent- or boat-shaped. Some analyzers now flag fragmented cells automatically, but the smear remains the reference method.

Shape changes arise in three ways. The marrow can build the cell wrongly, as in iron deficiency, thalassemia and megaloblastic anemia. The membrane can be inherited faulty or altered after release, as in hereditary spherocytosis and elliptocytosis, liver disease and after the spleen is removed. Or the cell can be damaged in the circulation, as in immune hemolysis, mechanical heart valves and the small-vessel clotting disorders that fragment cells. Artifacts also matter: blood stored for many hours in EDTA, a slowly dried or too-thick film, or a smear made near the edge of the slide can produce crenated (echinocyte) cells, teardrops all pointing the same way, or apparent fragments that are not present in fresh blood.

Normal range for Poikilocytosis

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

Group	Typical range (Semiquantitative grade on the smear (slight/1+ to marked/3+ or 4+); schistocytes and spherocytes may be reported as a percentage of red cells)	Notes
Normal smear	No poikilocytosis, or 'occasional' misshapen cells	A few oval, crenated or slightly irregular cells are seen in healthy blood and do not count.
Slight or 1+	A small minority of cells abnormally shaped	Common in mild iron deficiency, early B12 or folate deficiency, liver disease and after sample storage. Usually of no consequence when the hemoglobin is normal.
Moderate or 2+	A clear fraction of cells abnormal, often with named shapes	Established deficiency anemia, thalassemia trait with target cells, liver disease, hemolytic anemia. Nearly always with an abnormal MCV, RDW or hemoglobin.
Marked or 3+ (4+)	Most cells abnormal, frequently several shapes at once	Thalassemia major, myelofibrosis, severe iron deficiency, sickle cell disease, severe megaloblastic anemia, post-splenectomy, microangiopathic hemolysis.
Schistocytes (fragments)	Under about 0.5% of red cells is normal; 1% or more is significant in adults	The International Council for Standardization in Haematology treats 1% or more, with a low platelet count, as strong support for a thrombotic microangiopathy such as TTP or HUS.
Spherocytes	None in health	More than a few, with a raised MCHC and reticulocyte count, suggests hereditary spherocytosis or warm autoimmune hemolysis.
Elliptocytes	Under about 10% in health	Above about 25% suggests hereditary elliptocytosis; thin pencil forms in smaller numbers suggest iron deficiency.
Target cells	None or occasional in health	Numerous target cells point to liver disease, thalassemia, hemoglobin C or E, obstructive jaundice or an absent spleen.
Teardrop cells	None or occasional in health	Many, pointing in different directions, suggest marrow fibrosis or infiltration, thalassemia major or severe megaloblastic anemia. Tails all pointing the same way are an artifact of smear preparation.

Poikilocytosis present (1+ to 3+)

Poikilocytosis tells you that something has disturbed either how your red cells are built or how they are treated once in circulation. The grade gives a rough sense of how much of the red cell population is affected, but the specific shapes carry most of the diagnostic information, which is why it is worth reading the full smear comment rather than just the grade. Slight poikilocytosis with no particular shape named, a normal hemoglobin and a normal MCV is reported in many healthy people and in samples that waited several hours before being spread; it is not a diagnosis and rarely needs more than a repeat count.

When a shape is named, it narrows the field quickly. Pencil cells with small pale cells mean iron deficiency. Macro-ovalocytes with hypersegmented neutrophils mean vitamin B12 or folate deficiency. Target cells with small cells and a high red cell count mean thalassemia trait; target cells with large cells and raised liver enzymes mean liver disease. Spherocytes with a high MCHC and a high reticulocyte count mean hemolysis, either immune (a positive Coombs test) or hereditary (a negative one). Bite and blister cells after a new drug, an infection or fava beans mean oxidative hemolysis, most often G6PD deficiency. Teardrops with nucleated red cells and immature white cells (a leukoerythroblastic picture) mean the marrow is fibrosed or infiltrated and need prompt hematology review.

Two findings change the urgency. Schistocytes, red cell fragments, mean cells are being physically shredded. Small numbers occur with mechanical heart valves, severe burns, malignant hypertension and some cancers, but fragments together with a falling platelet count, a rising LDH and creatinine, confusion or fever suggest thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome or disseminated intravascular coagulation, all of which are treated as emergencies. Sickle cells on a smear in someone not already known to have sickle cell disease also need same-day follow-up, as they indicate a sickling disorder rather than sickle cell trait, which does not produce sickle cells on a routine smear.

Common causes

Iron deficiency
Produces small, pale cells with elongated pencil (cigar) forms and, when severe, target cells and marked anisocytosis. The commonest cause of mild to moderate poikilocytosis in adults; ferritin under 30 ng/mL confirms it.
Vitamin B12 or folate deficiency
Large oval cells (macro-ovalocytes) with teardrops and fragments in severe cases, nearly always with hypersegmented neutrophils (five or more lobes) on the same smear and an MCV above 100 fL.
Thalassemia and hemoglobin C, E or S
Thalassemia trait gives small cells with target cells and mild poikilocytosis; thalassemia intermedia and major give marked poikilocytosis with teardrops, fragments and nucleated red cells. Hemoglobin C and E produce abundant target cells; sickle cell disease produces sickle and boat-shaped cells, target cells and Howell-Jolly bodies once the spleen has stopped working.
Liver disease and alcohol
Altered membrane lipids produce target cells, stomatocytes and round macrocytes; in advanced cirrhosis, spiky acanthocytes (spur cells) appear and signal a severe hemolytic anemia with a poor prognosis.
Hereditary spherocytosis, elliptocytosis and other membrane disorders
Inherited defects in membrane proteins give spherocytes (with a raised MCHC, often above 36 g/dL) or more than 25% elliptocytes. Usually a lifelong mild anemia with gallstones and an enlarged spleen; hereditary elliptocytosis is often harmless.
Autoimmune and drug-induced hemolysis
Antibodies coat red cells, the spleen removes pieces of membrane and the surviving cells become spherocytes. Look for a positive direct Coombs (antiglobulin) test, high reticulocytes, high LDH and indirect bilirubin and low haptoglobin.
G6PD deficiency and other oxidative injury
Infections, fava beans and drugs such as dapsone, primaquine, nitrofurantoin and rasburicase oxidize hemoglobin into Heinz bodies, which the spleen bites out, leaving bite and blister cells. Common in people of African, Mediterranean, Middle Eastern and South Asian ancestry.
Microangiopathic hemolysis: TTP, HUS, DIC, HELLP, malignant hypertension
Fibrin strands in small vessels slice cells into schistocytes and helmet cells. Mechanical heart valves, extensive burns, vasculitis and metastatic cancer can do the same. Fragments with a low platelet count are an emergency until proven otherwise.
Myelofibrosis, marrow infiltration and myelodysplasia
A scarred or crowded marrow (primary myelofibrosis, metastatic cancer, lymphoma, tuberculosis, Gaucher disease) squeezes out teardrop cells and releases nucleated red cells and immature white cells. Myelodysplastic syndrome gives oval macrocytes, fragments and other odd shapes with low counts.
Kidney failure, absent spleen and artifact
Uremia produces evenly spiky echinocytes (burr cells). After splenectomy or in a non-working spleen, target cells, acanthocytes and Howell-Jolly bodies persist for life. Blood stored for many hours, slow drying and thick films also produce crenated cells and apparent teardrops.

Symptoms that can go with it

Often none; mild poikilocytosis is usually an incidental finding on a routine blood count
Fatigue, breathlessness on exertion, palpitations and pallor when anemia is present
Yellowing of the skin or eyes, dark (tea- or cola-colored) urine and pain under the left ribs from an enlarged spleen with hemolysis
Sudden back or abdominal pain, dark urine and weakness within a day or two of a new drug, an infection or eating fava beans in G6PD deficiency
Bruising, pinpoint red spots, confusion, fever or reduced urine output alongside fragments on the smear, which suggest TTP or HUS and need emergency care
Episodes of severe bone, chest or joint pain in sickle cell disease
Night sweats, weight loss, bone pain or fullness after small meals, which raise the possibility of a marrow or spleen disorder

Read it alongside

Anisocytosis and RDW — size variation usually accompanies shape variation; together they grade how disturbed red cell production is.
MCV and MCH — small, pale cells point to iron deficiency or thalassemia; large cells to B12, folate, liver disease, alcohol or marrow disease.
MCHC — a value above about 36 g/dL with poikilocytosis strongly suggests spherocytes (hereditary spherocytosis or immune hemolysis).
Platelet count — fragments plus a low platelet count is the combination that makes TTP, HUS or DIC likely and makes the result urgent.
Reticulocyte count — high when cells are being destroyed or lost and the marrow is responding; inappropriately low when the marrow itself is the problem.
LDH, indirect bilirubin and haptoglobin — the hemolysis screen; a high LDH and bilirubin with a haptoglobin below about 25 mg/dL confirms red cell destruction.
Ferritin, vitamin B12 and folate — the nutritional causes that explain most mild to moderate poikilocytosis.
Hemoglobin electrophoresis and a direct Coombs test — ordered when target or sickle cells, or spherocytes, respectively, appear on the smear.

What usually happens next

If the comment is 'slight' or '1+' with no named shapes and your hemoglobin, MCV and platelets are normal, the usual plan is a repeat CBC in a few months and a ferritin if there is any reason to suspect low iron.
If pencil cells, target cells or small pale cells are described, expect ferritin, iron saturation and TIBC, and hemoglobin electrophoresis if iron is normal and the red cell count is high.
If spherocytes, bite cells or fragments are described, expect a hemolysis work-up the same day: reticulocyte count, LDH, bilirubin, haptoglobin, direct Coombs test, creatinine and a coagulation screen, and a G6PD level if bite cells are seen.
If teardrop cells, nucleated red cells or immature white cells are described, expect prompt referral to hematology; a bone marrow biopsy is often the next test.
Ask whether the smear was made from fresh blood. If the sample was several hours old or sent from a distance, a repeat smear from a fresh draw sometimes removes the finding altogether.

Diet, lifestyle and natural levers with evidence

What can move Poikilocytosis once the cause is known. Nothing here replaces finding the cause.

Correct iron deficiency when ferritin is low

Strong evidence

Pencil cells and the associated anisocytosis disappear once iron stores are rebuilt and the abnormal cells have been replaced, which takes two to four months. Oral iron raises hemoglobin by roughly 1 g/dL every two to three weeks; alternate-day dosing of 60 to 100 mg elemental iron improves absorption per dose by about a third and reduces side effects. Heme iron from meat, poultry and fish is absorbed several times better than plant iron, and tea or coffee taken with a meal can cut non-heme iron absorption by half or more.

Do not take iron for poikilocytosis without a confirmed low ferritin; in thalassemia and hemolytic anemias, iron stores are often already high.

Vitamin B12 and folate repletion

Strong evidence

Macro-ovalocytes, teardrops and fragments from megaloblastic anemia clear within about eight weeks of adequate replacement. A Cochrane review found oral B12 at 1,000 to 2,000 µg a day as effective as injections for raising levels and correcting anemia; folic acid 400 µg to 1 mg a day corrects folate deficiency. Folate needs are higher in any chronic hemolytic anemia (sickle cell disease, hereditary spherocytosis, thalassemia) because red cell turnover is several times normal, and many clinicians recommend a daily supplement in those conditions.

Always check B12 before taking folic acid for macrocytosis; folate alone can mask B12 deficiency while nerve damage continues.

Reduce alcohol intake

Moderate evidence

Alcohol is the most common cause of target cells, stomatocytes and round macrocytes in people who are not anemic, through a direct effect on the developing cell and on membrane lipids. Observational studies show these changes in a large share of people drinking more than about four drinks a day, and they reverse over two to four months of abstinence. In established cirrhosis, the smear changes persist because the liver damage itself drives them.

L-glutamine in sickle cell disease

Moderate evidence

In a 48-week randomized trial of 230 people with sickle cell disease, pharmaceutical-grade L-glutamine (0.3 g/kg twice daily) reduced the median number of pain crises from 4 to 3 (about 25 percent fewer), hospitalizations from 3 to 2 and acute chest syndrome from 23 to 9 percent, by reducing oxidative damage to sickle red cells. It is a prescription product in the US and is used alongside, not instead of, standard treatment.

Nausea, constipation and headache are common; it has not been studied in kidney or liver impairment. Discuss with your sickle cell team before starting.

When to see a clinician promptly

Schistocytes (fragments) on the smear with a low or falling platelet count, especially with fever, confusion, headache, reduced urine, bruising or pinpoint red spots: possible TTP or HUS, which is a medical emergency.
Poikilocytosis with a hemoglobin under 8 g/dL, or any anemia with chest pain, breathlessness at rest, fainting or a racing heart.
Sudden dark urine, jaundice, back or abdominal pain and weakness within days of a new medicine, an infection or eating fava beans: possible acute hemolysis.
Sickle cells seen on a smear in someone not known to have sickle cell disease, or severe bone, chest or abdominal pain, breathlessness or stroke-like symptoms in someone who has it.
Teardrop cells with nucleated red cells or immature white cells, or poikilocytosis with unexplained weight loss, night sweats, bone pain or a swollen abdomen.
Marked (3+) poikilocytosis, or poikilocytosis that persists on a fresh sample three months after treating a confirmed iron, B12 or folate deficiency.

Frequently asked questions

What does poikilocytosis 1+ mean?

It means the person examining your smear saw a small excess of abnormally shaped red cells, the lowest grade on a 1+ to 3+ (or 4+) scale. When no particular shape is named and your hemoglobin, MCV and platelets are normal, it is a common finding, often reflecting mild iron deficiency, minor illness or a sample that waited a few hours before the slide was made. It is a prompt to check ferritin if you have a reason to be low in iron, not a diagnosis in itself.

Is mild poikilocytosis serious?

Usually not. Mild poikilocytosis is seen in healthy people, in mild nutritional deficiency, in pregnancy, in liver disease and after sample storage. It becomes significant when you are anemic, when the MCV or MCHC is abnormal, or when specific shapes are named, particularly schistocytes, spherocytes, sickle cells or teardrop cells. Those shapes point to conditions that need prompt attention, regardless of the grade.

What causes poikilocytosis?

The common causes are iron deficiency, vitamin B12 or folate deficiency, liver disease and alcohol, and thalassemia or other hemoglobin disorders. Less common but important causes are hemolytic anemias (hereditary spherocytosis, autoimmune hemolysis, G6PD deficiency), sickle cell disease, mechanical fragmentation of red cells (TTP, HUS, DIC, heart valves), bone marrow fibrosis or infiltration, kidney failure and an absent spleen. Blood stored for many hours before the smear is made can also produce artifactual shape changes.

What is the difference between anisocytosis and poikilocytosis?

Anisocytosis is variation in red cell size and is also measured by the RDW on the automated count. Poikilocytosis is variation in shape and can only be seen on the smear. They often occur together because the same disorders disturb both, but shape is usually more specific: a report of 'anisocytosis 2+, poikilocytosis 2+ with pencil cells' says iron deficiency; 'with target cells' says liver disease or thalassemia; 'with schistocytes' says mechanical destruction.

What do target cells, teardrop cells and schistocytes mean?

Target cells (a bullseye of hemoglobin in the pale center) come from too much membrane for the cell's contents and point to liver disease, thalassemia, hemoglobin C or E, obstructive jaundice or an absent spleen. Teardrop cells (one tapered tail) point to a scarred or crowded bone marrow such as myelofibrosis or marrow infiltration, or to thalassemia major or severe megaloblastic anemia. Schistocytes (sharp-edged fragments and helmet cells) mean red cells are being physically torn apart; more than about 1% with a low platelet count suggests TTP, HUS or DIC and is urgent.

Can poikilocytosis go away?

Yes, if the cause is reversible. Shape changes from iron, B12 or folate deficiency, alcohol and acute hemolysis resolve over two to four months once the cause is treated, because the abnormal cells are gradually replaced. Poikilocytosis from inherited conditions (thalassemia, hereditary spherocytosis, sickle cell disease) and from an absent spleen is lifelong, and in those cases it is simply part of the expected picture rather than a sign of deterioration.

Does poikilocytosis mean cancer or leukemia?

Rarely. The vast majority of poikilocytosis is nutritional, inherited, hepatic or artifactual. The pattern that raises concern for a marrow disorder is teardrop cells together with nucleated red cells and immature white cells (a leukoerythroblastic smear), or marked poikilocytosis with macrocytosis and low white cell or platelet counts that no deficiency explains, usually in older adults. That picture warrants a hematology referral, but even then the causes include non-cancerous conditions such as myelofibrosis, infection and severe deficiency.

Can the blood sample itself cause poikilocytosis?

Yes. Red cells stored in EDTA for many hours become crenated (echinocytes), and a film that dries slowly, is spread too thickly or is examined near its edges can show artificial teardrops, fragments and spherocyte-like cells. Teardrops that all point the same direction are a classic preparation artifact. If a mild finding does not fit your other results, a repeat smear made promptly from a fresh draw is a reasonable first step.

References

Blood smear. MedlinePlus, US National Library of Medicine (2023)View source
Bain BJ. Diagnosis from the blood smear. New England Journal of Medicine (2005)
Palmer L, Briggs C, McFadden S, et al.. ICSH recommendations for the standardization of nomenclature and grading of peripheral blood cell morphological features. International Journal of Laboratory Hematology (2015)
Zini G, d'Onofrio G, Briggs C, et al.. ICSH recommendations for identification, diagnostic value, and quantitation of schistocytes. International Journal of Laboratory Hematology (2012)
Ford J. Red blood cell morphology. International Journal of Laboratory Hematology (2013)
Overview of hemolytic anemia. Merck Manual Professional Version (2024)
Evaluation of anemia. Merck Manual Professional Version (2024)
Lynch EC. Peripheral blood smear (Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd edition). Butterworths; NCBI Bookshelf (1990)
Niihara Y, Miller ST, Kanter J, et al.. A phase 3 trial of L-glutamine in sickle cell disease. New England Journal of Medicine (2018)
Joly BS, Coppo P, Veyradier A. Thrombotic thrombocytopenic purpura. Blood (2017)
Perrotta S, Gallagher PG, Mohandas N. Hereditary spherocytosis. Lancet (2008)
Camaschella C. Iron-deficiency anemia. New England Journal of Medicine (2015)

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This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.