Low Hemoglobin in Cancer: What It Means and Next Steps

Low hemoglobin (anemia) is common in people with cancer and often relates to the disease itself or its treatments. Hemoglobin helps red blood cells carry oxygen; when it’s low, the body gets less oxygen, leading to fatigue and shortness of breath. ^[1] Anemia is generally defined as a hemoglobin level below about 12 g/dL in adults, and many cancer‑related cases fall in the 7–11 g/dL range. ^[2] Symptoms vary, but tiredness can be significant and may affect daily life. ^{[1] [3]}

Why hemoglobin drops in cancer

• Cancer and inflammation: Tumors and inflammation can impair red blood cell production and iron handling. This reduces hemoglobin. [PM11]
• Chemotherapy effects: Myelosuppressive chemotherapy can lower bone marrow production of red blood cells, causing anemia. [PM9]
• Iron deficiency: Bleeding, poor intake, or iron sequestration can lead to absolute or functional iron deficiency. Both can reduce hemoglobin and are treatable. [PM11]
• Other causes: Nutritional deficits (B12/folate), kidney issues (less erythropoietin), or bleeding from the tumor or surgery may contribute. [PM11]

How it may feel

• Common symptoms: Fatigue, shortness of breath with activity, dizziness, palpitations, headaches, and pale skin are typical; not everyone has all symptoms. ^{[1] [4]}
• Impact on daily life: Fatigue from anemia can strongly affect quality of life and emotional well‑being. Large surveys show fatigue is frequent and burdensome in cancer. [PM29]

Does low hemoglobin affect outcomes?

Low hemoglobin has been linked to worse treatment responses and survival in several cancers, and maintaining adequate levels can be beneficial. ^[5] [PM29] In some settings, higher pre‑treatment hemoglobin has been associated with better outcomes, such as in anal squamous cell carcinoma. ^[6] These are general associations and may vary by cancer type and overall health.

When to be concerned

• Rapid declines or very low levels (around or below 7–8 g/dL) can be more serious and may require urgent evaluation. Transfusion thresholds are individualized but often considered at lower hemoglobin with symptoms. [PM9]
• New or worsening symptoms like chest pain, severe shortness of breath, lightheadedness, or signs of bleeding should prompt immediate medical contact. ^[4]

How anemia is evaluated

• Blood tests: Complete blood count (CBC) for hemoglobin/hematocrit; iron studies (ferritin, transferrin saturation) to detect iron deficiency; B12 and folate when indicated. Iron deficiency can be absolute (low ferritin) or functional (low transferrin saturation with normal/high ferritin). [PM11]
• Medication and treatment review: Assess recent chemotherapy and other drugs that can lower blood counts. [PM9]
• Check for bleeding: Especially in gastrointestinal or surgical contexts. [PM11]

Treatment options

Management depends on cause, cancer plan, and symptom severity. Goals are to improve symptoms and reduce transfusion needs while balancing risks. [PM9] [PM19]

• Red blood cell transfusion: Quickly raises hemoglobin and relieves symptoms; kept to a minimum due to risks and resource considerations. [PM11]
• Iron therapy: Intravenous iron is often preferred in cancer‑related absolute or functional iron deficiency and can enhance response to erythropoietic agents and reduce transfusions. [PM11] [PM18]
• Erythropoiesis‑stimulating agents (ESAs, e.g., epoetin, darbepoetin): For anemia due to myelosuppressive chemotherapy when the aim is to avoid transfusions. Use the lowest effective dose and generally target around 12 g/dL to minimize transfusion needs. [PM19] ESAs carry risks, including blood clots and possible tumor effects, so they are used selectively and according to labeling and guidelines. ^{[7] [8]}
• Treat underlying causes: Address B12/folate deficiency, manage bleeding, optimize nutrition, and adjust contributing medications when possible. [PM11]

Practical steps you can take

• Report symptoms early: Don’t “power through” severe fatigue or breathlessness; these can be signs of anemia. Request a CBC to check hemoglobin if symptoms rise. ^[3]
• Ask about iron status: If hemoglobin is low, ask whether iron studies have been done and whether IV iron could help. IV iron can be useful even when ferritin is normal but transferrin saturation is low (functional deficiency). [PM11]
• Discuss ESA appropriateness: If you’re on myelosuppressive chemotherapy and symptomatic anemia persists, ask whether ESAs are suitable in your specific situation, considering risks and goals of treatment. They should be used only in chemotherapy‑induced anemia and at the lowest dose to avoid transfusions. ^{[7] [8]}
• Understand thresholds: Clarify your team’s transfusion thresholds and plan, especially if you have heart or lung disease where higher hemoglobin may be needed. Strategies aim to improve symptoms and safety. [PM9]

At a glance: anemia in cancer

Topic	Key points
Definition	Hemoglobin below ~12 g/dL is typically considered anemia in adults. [2]
Common symptoms	Fatigue, shortness of breath, dizziness, palpitations, headaches, pallor. [1] [4]
Causes	Cancer/inflammation, chemotherapy, iron deficiency, B12/folate deficiency, bleeding, kidney issues. [PM11] [PM9]
Risks	Reduced quality of life; associations with poorer outcomes in several cancers. [PM29] [5]
Evaluation	CBC, iron studies, B12/folate, review of chemo and bleeding risks. [PM11] [PM9]
Treatments	Transfusion (as needed), IV iron for deficiency, selective ESA use in chemo‑induced anemia, treat underlying causes. [PM11] [PM19] [7] [8]

Bottom line

Low hemoglobin in cancer is common and often manageable with the right work‑up and treatment plan. [PM9] You don’t have to ignore significant fatigue there are evidence‑based options like IV iron, transfusion when needed, and carefully selected ESAs to improve symptoms and reduce risks. [PM11] [PM19] Talk with your care team about recent hemoglobin levels, iron status, and the safest strategy tailored to your cancer treatment and overall health. ^[3]