Low hemoglobin and anemia are common in cancer patients and may result from bone marrow involvement, chronic inflammation, blood loss, or cancer treatment. This article explains which cancers cause anemia, how it is diagnosed, and available treatment options.
With cancer comes a host of symptoms that make patients and caregivers wonder, 'Is it my cancer causing this?' One such symptom is anemia, a condition in which the body does not have enough hemoglobin to carry oxygen and nutrients to various organs and tissues. The hemoglobin threshold to diagnose anemia varies with gender, age, and pregnancy status. Normal hemoglobin levels are approximately 14-16 g/dL for men and 12-15 g/dL for women.
Key Takeaways
• Low hemoglobin (anemia) is common in cancer patients and can result from bone marrow involvement, chronic inflammation, blood loss from tumors, or cancer treatment such as chemotherapy.
• Six categories of cancer cause low hemoglobin: hematological cancers (leukemia, lymphoma, myeloma, MDS), solid tumors causing blood loss, cancers causing chronic inflammation, tumors that infiltrate the bone marrow, chemotherapy and radiation effects, and kidney cancer affecting erythropoietin production.
• A complete blood count (CBC) is the primary test for detecting anemia, and additional tests such as iron studies, ferritin, vitamin B12, folate levels, and bone marrow biopsy may be needed to identify the cause.
• Low hemoglobin in cancer patients is associated with decreased quality of life and shorter survival times; approximately 39% of cancer patients have anemia at any given time, and up to 90% may experience it at some point during treatment.
• Treatment depends on the cause and may include iron supplementation, blood transfusions, or erythropoiesis-stimulating agents (ESAs). Persistently low hemoglobin that does not improve with standard treatment should be evaluated for an underlying malignancy.
Signs and Symptoms of Anemia in Cancer Patients
Anemia can manifest in various ways. Some common symptoms that anemia can cause include:
- Fatigue
- Feeling dizzy or light-headed
- Headaches
- Shortness of breath, especially after exercise
- Cold hands or feet
- Brittle nails
- Rapid heartbeat
- Weakness
- Pica (unusual cravings for non-food items such as ice)
If anemia is severe, it can lead to more critical symptoms and signs such as:
- Rapid breathing and heart rate
- Pale skin
- Loss of consciousness and falls
What Types of Cancer Cause Low Hemoglobin?
Several different types of cancer can cause low hemoglobin, and this may be related to chronic inflammation, direct infiltration of the bone marrow by tumor cells or fibrous tissue as a result of cancer, nutrient deficiencies, chemotherapy, or blood loss.
The cancers that cause anemia can be differentiated into hypoproliferative or hyperproliferative.
1. Hypoproliferative Anemia
Occurs when the bone marrow is unable to produce enough cells. This will have a low reticulocyte count, which is a marker of how well the bone marrow can produce red blood cells. Causes of hypoproliferative anemia include destruction of the bone marrow itself by tumor, fibrous tissue, chemotherapy, or other toxins, or nutritional deficiencies, where the bone marrow does not have enough substrate to manufacture red blood cells.
2. Hyperproliferative Anemia
This can be due to blood loss or blood cell destruction in the circulating blood. In this form of anemia, the bone marrow, or the site of production, is not affected, and the reticulocyte count is generally higher, as the bone marrow tries to produce more red blood cells to compensate for the loss.
6 Categories of Cancer That Lower Hemoglobin
1. Hematological Cancers
These cancers directly affect blood cell production and can lead to low hemoglobin counts due to bone marrow dysfunction. These include: leukemia, lymphoma, multiple myeloma, and myelodysplastic syndromes.
2. Solid Cancers Causing Blood Loss
These cancers lead to slow, continuous bleeding, such as bleeding with bowel movements, dark-colored stools, increased vaginal bleeding, or bloody urine. These cancers include: colorectal cancer, stomach cancer, cervical cancer, ovarian cancer, and bladder cancer.
Some cancers can also rupture or hemorrhage and cause internal bleeding. Examples include hepatocellular (liver) cancer and Gastrointestinal stromal tumors (GIST) involving the stomach, where stomach cancer symptoms such as anemia often result from chronic blood loss.
3. Cancers Causing Chronic Inflammation
One of the reasons anemia develops in cancer patients is chronic inflammation. This type of anemia is generally referred to as anemia of chronic disease. Several different types of cancers can lead to a chronic inflammatory state, resulting in decreased blood cell production.
4. Solid Tumors Affecting Bone Marrow
Some tumors can affect the bone marrow due to infiltration by metastatic cancer or due to abnormal fibrous tissue replacing the normal tissue that produces red blood cells. This specific type of anemia is called myelophthisic anemia. It includes breast cancer, prostate cancer, and lung cancer
5. Chemotherapy and Radiation-Related Anemia
Chemotherapy, or the medications given to suppress malignant cells, can have several adverse effects. One unfortunate side effect is anemia. Radiation therapy can also affect the bone marrow and cause low hemoglobin.
6. Kidney Cancer Affecting Erythropoietin Production
Erythropoietin is a hormone produced by the kidneys that stimulates the bone marrow to produce more blood cells. Kidney cancer can lead to lower erythropoietin production, thus leading to anemia.
Understanding Your Blood Test Results: Hemoglobin, Hematocrit, and Related Values
When a blood test shows low hemoglobin, other related values on the complete blood count (CBC) are often abnormal as well. Understanding what these values mean can help patients and caregivers make sense of their lab results.
Hematocrit (HCT) measures the percentage of blood volume made up of red blood cells. Because red blood cells carry hemoglobin, hematocrit typically drops alongside hemoglobin. A low hematocrit confirms that the body has fewer red blood cells than normal.
Mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) reflect the amount of hemoglobin inside individual red blood cells. When MCH and MCHC are low, it often points to iron deficiency as a contributing cause of anemia, which is common in cancers that cause chronic blood loss such as colorectal or stomach cancer.
Red cell distribution width (RDW) measures variation in the size of red blood cells. An elevated RDW can suggest iron deficiency, vitamin B12 deficiency, or a mixed cause of anemia. In cancer patients, an abnormal RDW may indicate that the bone marrow is responding to blood loss by releasing immature red blood cells of varying sizes.
When hemoglobin, hematocrit, MCH, and MCHC are all low together, doctors use these values in combination with iron studies and a peripheral blood smear to determine whether the anemia is caused by iron deficiency, chronic disease, bone marrow infiltration, or another mechanism.
How Is Anemia Diagnosed in Cancer Patients?
Important laboratory tests that are performed while evaluating patients with cancer include a complete blood count, a peripheral blood smear, which allows assessment of blood cell abnormalities, and possibly a bone marrow biopsy if further evaluation is needed.
Ruling out nutritional deficiencies such as iron, vitamin B12, and folate is important, as this is an easily correctable cause of anemia.
Iron studies, including serum ferritin, serum iron, total iron-binding capacity (TIBC), and transferrin saturation, help distinguish iron deficiency anemia from anemia of chronic disease. Low ferritin typically indicates true iron deficiency, while normal or elevated ferritin with low serum iron suggests anemia of chronic inflammation. When hemoglobin and platelets are both low (a condition called pancytopenia), it may indicate that the bone marrow is directly affected by cancer and further evaluation with a bone marrow biopsy is often necessary.
How Is Anemia Treated in Cancer Patients?
The treatment of anemia depends on the underlying cause and must be weighed carefully against possible risks and benefits.
Anemia due to nutritional deficiencies, such as iron, can be treated with oral iron supplementation, which is generally well-tolerated.
Transfusions are considered when hemoglobin falls below a certain threshold (generally below 7 g/dL) and can be given as needed.
Erythropoiesis-stimulating agents (agents that can stimulate increased red blood cell growth) have their own set of risks and benefits and are administered on a case-by-case basis.
In addition to medical treatment, patients can support their hemoglobin levels by eating iron-rich foods (such as red meat, beans, spinach, and fortified cereals), ensuring adequate vitamin B12 and folate intake, staying hydrated, and avoiding excessive alcohol, which can suppress bone marrow function. Patients should report any new or worsening symptoms such as increased fatigue, shortness of breath, or dizziness to their care team promptly.
What Else Causes Anemia? Non-Cancer Factors That Lower Hemoglobin
Anemia can be caused by many factors. Poor nutrition is one of the most common causes of anemia, such as iron deficiency. Other causes include infections, blood loss, such as heavy menstruation, chronic diseases, inherited disorders of blood cells, and many more.
As the bone marrow is the site of production of red blood cells, damage to the bone marrow, either directly or indirectly, can lead to anemia.
The Impact of Anemia on Cancer Patients
Cancer-associated anemia decreases the quality of life in patients with cancer and also affects the type of treatment they receive. Importantly, it has also been shown to be associated with shorter survival times. A large multinational prospective study showed that approximately 39% of patients with cancer were anemic. Gynecological cancer had the largest proportion of anemic patients, followed by lung cancer, and then lymphoma/myeloma. The study also found an increased likelihood of developing anemia with longer durations of chemotherapy. Overall, up to 90% of cancer patients may experience anemia at some point during their treatment, making it one of the most common complications of cancer care.
If you are experiencing any signs or symptoms of anemia, please consult your healthcare provider for personalized recommendations.
When Should Low Hemoglobin Raise Concern About Cancer?
Low hemoglobin does not always indicate cancer. Most cases of anemia are caused by iron deficiency, nutritional factors, chronic diseases, or blood loss from non-cancerous sources. However, anemia that develops without a clear explanation, does not improve with standard treatment such as iron supplements, or is accompanied by other symptoms such as unexplained weight loss, persistent fatigue, or abnormal bleeding should be evaluated further.
Persistently low hemoglobin, particularly levels that remain below 10 g/dL despite treatment, may warrant additional investigation including imaging, endoscopy, or a bone marrow biopsy to rule out an underlying malignancy. Patients with a family history of blood cancers or those who have previously undergone cancer treatment should discuss their anemia with an oncologist or hematologist.
Frequently Asked Questions
Does low hemoglobin always mean cancer?
No. Low hemoglobin (anemia) has many possible causes, and cancer is only one of them. Iron deficiency from poor diet or blood loss, vitamin B12 or folate deficiency, chronic kidney disease, infections, and inherited blood disorders such as sickle cell disease or thalassemia are all common non-cancer causes of anemia. However, if anemia persists without a clear explanation or does not respond to standard treatment, further evaluation is appropriate to rule out an underlying malignancy.
Can low hemoglobin be the first sign of cancer?
Yes, in some cases. Anemia can be one of the earliest detectable signs of certain cancers, particularly blood cancers such as leukemia, lymphoma, and multiple myeloma, where abnormal cells crowd out healthy blood-forming cells in the bone marrow. It can also be an early sign of gastrointestinal cancers such as colon or stomach cancer, where slow, chronic bleeding from a tumor leads to iron deficiency anemia before other symptoms appear. This is why unexplained anemia, especially in adults over 50, is often investigated with additional tests.
What does it mean when hemoglobin and hematocrit are both low?
When both hemoglobin and hematocrit are low, it confirms that the body has fewer red blood cells or less hemoglobin than normal, a condition broadly defined as anemia. The two values almost always move together because hematocrit measures the proportion of blood occupied by red blood cells, and hemoglobin is the oxygen-carrying protein inside those cells. The next step is to determine why they are low by examining additional blood test values such as MCH, MCHC, RDW, iron studies, and reticulocyte count, which help narrow down whether the cause is iron deficiency, chronic disease, bone marrow problems, or another factor.
About Author
Chandra Kakarala, MBBS, is an internal medicine resident interested in hematology/oncology, global health, and medical education. She is passionate about improving cancer detection rates and preventive care.
Works Discussed
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