Anemia Tests: Which Blood Tests Find Anemia and Its Cause?
A CBC can identify anemia, but finding the cause often requires ferritin, iron studies, a reticulocyte count, or other follow-up tests.
Medically reviewed by Rhonda Collins, FNP-C | Mito Health on August 27, 2026.
The usual first blood test for anemia is a complete blood count (CBC). It measures hemoglobin, hematocrit, red blood cell count, and red blood cell indices. A CBC can show that anemia is present, but it usually cannot identify the cause on its own. Ferritin, iron studies, a reticulocyte count, vitamin B12, folate, and other tests answer different follow-up questions.
What blood test shows anemia?
A complete blood count is the standard starting point for checking whether the blood has enough healthy red blood cells to carry oxygen. The National Heart, Lung, and Blood Institute identifies four CBC measurements that help assess anemia:
- Hemoglobin measures the oxygen-carrying protein inside red blood cells.
- Hematocrit measures the proportion of blood made up of red blood cells.
- Red blood cell count measures the number of red blood cells in the sample.
- Mean corpuscular volume (MCV) describes the average size of those cells.
These results establish a pattern, not a complete explanation. Age, pregnancy, altitude, medical history, and the laboratory’s own reference interval can affect how a result should be interpreted.
Which anemia test answers which question?
No single test identifies every type or cause of anemia. The useful next test depends on what the CBC shows and why anemia is suspected.
| Test | What it helps answer | What it cannot establish alone | | --- | --- | --- | | CBC with red cell indices | Is anemia present, and are red cells smaller, larger, or otherwise unusual? | The underlying cause | | Ferritin | Are the body’s stored iron levels low? | Whether a high result reflects excess iron; interpret it with other iron markers and clinical context | | Iron, TIBC, and transferrin saturation | How much iron is circulating and available for transport? | The cause of an abnormal pattern without clinical context | | Reticulocyte count | Is bone marrow releasing an expected number of young red blood cells? | Why production or loss is abnormal | | Vitamin B12 and folate | Could one of these nutrient deficiencies contribute to the blood-count pattern? | Other possible causes of anemia |
MedlinePlus explains that a reticulocyte count measures young red blood cells and can help assess whether bone marrow is making red blood cells at the expected rate. Its result is interpreted with the CBC, history, and other tests.
A CBC checks for anemia. Ferritin checks iron stores
Anemia and iron deficiency are related but not interchangeable. Anemia describes reduced oxygen-carrying capacity in the blood. Iron deficiency is one possible cause, and iron stores can become low before the CBC meets criteria for anemia.
A ferritin test measures a protein that stores iron. MedlinePlus describes ferritin testing as part of an iron assessment that can help investigate iron deficiency anemia. Ferritin can also rise for reasons unrelated to iron stores, including inflammation and some liver or chronic conditions, so it should not be interpreted in isolation.
If the visitor’s question is specifically about iron stores, the exact commercial handoff is the Mito ferritin test. If the question is whether anemia is present, start with the CBC with differential and platelets.
How clinicians investigate the cause after a CBC
The next step is guided by the CBC pattern, symptoms, history, and risk factors. The American Society of Hematology notes that an iron-deficiency evaluation can include a CBC plus ferritin, serum iron, total iron-binding capacity, transferrin, or transferrin saturation. The NHLBI also describes blood smears, reticulocyte counts, iron tests, and other targeted testing as possible follow-up after anemia is identified.
Examples of cause-directed follow-up include:
- ferritin and iron studies when iron deficiency or altered iron handling is plausible;
- vitamin B12 and folate when the red-cell pattern or history supports those possibilities;
- a reticulocyte count when the question is whether marrow production is responding as expected;
- kidney, inflammation, bleeding, hemolysis, or inherited-condition testing when the history and initial results point in those directions.
An abnormal result deserves a cause-focused evaluation. Starting iron or another supplement before the cause is clear can delay that evaluation and may be inappropriate when the deficiency is not present.
Can you test for anemia at home?
Some home devices estimate hemoglobin from a finger-stick sample, while mail-in kits may measure selected markers in a laboratory. The marker set matters more than the label on the box. A hemoglobin-only result can screen one part of the question, but it does not measure ferritin or explain why hemoglobin may be abnormal.
How to prepare for anemia bloodwork
A CBC generally does not require fasting. Preparation can change when it is ordered alongside iron tests or other bloodwork. MedlinePlus advises following the instructions for the exact tests ordered and notes that a provider may request fasting before a ferritin test. Do not fast, stop medication, or change supplements solely because of general internet advice. Follow the instructions attached to the order.
When symptoms need prompt medical attention
Testing is not the right first step for severe or rapidly worsening symptoms. Seek urgent medical care for chest pain, severe shortness of breath, fainting, confusion, signs of major bleeding, or a fast or irregular heartbeat with weakness. For persistent fatigue, breathlessness, dizziness, heavy bleeding, or an abnormal home result, arrange a clinician evaluation rather than relying on a single self-ordered marker.
Anemia test questions
What is the main test for anemia? A CBC is the usual starting test. It measures hemoglobin, hematocrit, red blood cells, and indices such as MCV.
Does a CBC include ferritin? No. Ferritin is a separate test of stored iron. A CBC can show an anemia pattern, while ferritin helps answer whether low iron stores may be involved.
Can a ferritin test diagnose anemia? Ferritin can support an iron-deficiency evaluation, but anemia itself is assessed with blood-count measurements such as hemoglobin and hematocrit.
Which tests check iron-deficiency anemia? A clinician may use a CBC with ferritin and other iron studies. The appropriate combination depends on the initial results and clinical context.
Should everyone order every anemia-related test? No. A broad bundle can produce findings that are hard to interpret and may still miss the relevant cause. Start with the test that matches the question, then use the initial result and clinical context to guide follow-up.
Related guides
- CBC Test Cost: What a Complete Blood Count Costs Across Labs
- Ferritin Test Cost: What a Ferritin Test Costs Across Labs
- Iron Panel Cost: Iron, TIBC and Saturation Prices
- Vitamin B12 Deficiency Diagnosis
Medical disclaimer
This guide is for informational purposes only. It does not diagnose anemia, identify its cause, or replace medical care. A qualified clinician should interpret abnormal results in the context of symptoms, history, examination, and other testing.
