Low Hemoglobin: What It Means and What to Do Next
Low hemoglobin means your blood is carrying less of the protein that moves oxygen around your body, which is the definition of anemia. Quest's adult reference ranges are 13.2–17.1 g/dL for men and 11.7–15.5 g/dL for women, but go by the range printed on your report. The most common cause is iron deficiency, often from heavy periods, pregnancy or slow bleeding in the gut. Low B12 or folate, chronic inflammation, kidney disease and inherited conditions such as thalassemia trait are other common causes. The MCV (red cell size) on the same CBC is the quickest clue to which one it is.
What Causes Low Hemoglobin?
Iron Deficiency
The most common cause worldwide. Heavy periods, pregnancy, frequent blood donation, a low-iron diet and poor absorption (celiac disease, weight-loss surgery) all deplete iron. Red cells are usually small (low MCV) and ferritin is low.
Blood Loss
Slow bleeding from the stomach or bowel, from ulcers, NSAID use, polyps or cancer, can cause anemia with no visible blood. In men and in women after menopause, iron-deficiency anemia should prompt a check of the gut.
B12 or Folate Deficiency
Without enough B12 or folate the marrow makes fewer, larger red cells (high MCV). Causes include a vegan diet, pernicious anemia, metformin, heavy drinking and gut conditions.
Chronic Inflammation or Disease
Long-term conditions such as rheumatoid arthritis, inflammatory bowel disease, chronic infections and cancer reduce how well the body uses its iron. Red cells are usually normal-sized and ferritin can be normal or high.
Kidney Disease
The kidneys make erythropoietin (EPO), the hormone that tells the marrow to make red cells. As kidney function falls, so does hemoglobin.
Pregnancy
Blood volume expands in pregnancy, which dilutes hemoglobin, and the baby's needs use up iron. Anemia in pregnancy is common and is screened for routinely.
Inherited Conditions
Thalassemia trait causes mild anemia with very small red cells and normal iron, and is often mistaken for iron deficiency. Sickle cell disease and other inherited conditions are less common causes.
Hemolysis and Bone-Marrow Problems
Less often, red cells are destroyed early (by antibodies, some medications or an enzyme deficiency such as G6PD) or the marrow does not make enough of them. These usually show other abnormal counts.
Associated Symptoms
What to Do Next
1. Retest to confirm
A single abnormal result should be confirmed with a repeat test. Temporary factors like stress, illness, or medications can affect results.
2. Related tests to consider
3. When to see a doctor
If your Hemoglobin is significantly abnormal, if you have severe symptoms, or if repeated results confirm the abnormality, consult a healthcare professional for appropriate evaluation and treatment.
Related Conditions
Frequently Asked Questions
This page is for informational purposes only and does not constitute medical advice. Consult a healthcare provider for interpretation of your results.
Content reviewed for accuracy by the JustLabs editorial team.