Hemoglobin · low result
Low hemoglobin: what it means, causes, symptoms and what to check next
Short answer
Low hemoglobin is anemia — below about 13.0–13.5 g/dL in men and 12.0 in non-pregnant women on most lab ranges. The red cell size (MCV) points to the type: small cells suggest iron deficiency or thalassemia trait; large cells suggest vitamin B12 or folate deficiency, alcohol, liver or thyroid disease, or certain medications; normal-sized cells suggest recent blood loss, chronic disease or inflammation, kidney disease, or a marrow problem. Iron deficiency — from heavy periods or slow gut blood loss — is the most common cause, which is why ferritin is the first test added. Severity and speed matter: a hemoglobin that has drifted to 11 over months is a different situation from one that has fallen to 8 in weeks.
Medically reviewed by Youmna DiStefano, MD · Last reviewed November 2026
When does this result need same-day care?
- Hemoglobin below about 8 g/dL, or any low value with chest pain, breathlessness at rest, fainting or confusion — same-day care
- Black, tarry or bloody stools, or vomiting blood — emergency care; this is active bleeding
- A fast fall from a previously normal value within days to weeks, or anemia with fever, bruising or bleeding gums
What is the normal range for Hemoglobin?
- Male, age 18+: 13.5 – 17.5 g/dL
- Female, age 18+: 12.0 – 15.5 g/dL
Commonly associated with anemia from iron deficiency, blood loss, chronic disease, or certain vitamin deficiencies.
Full reference table, citations and testing options: Hemoglobin biomarker page.
What are the common causes of low Hemoglobin?
- Iron deficiency — heavy menstrual bleeding, gastrointestinal blood loss (ulcers, aspirin and NSAIDs, polyps or colon cancer, hemorrhoids, inflammatory bowel disease), low intake, celiac disease, bariatric surgery
- Vitamin B12 or folate deficiency — pernicious anemia, metformin, long-term acid suppressants, alcohol, poor diet
- Recent or occult blood loss — surgery, trauma, heavy periods, slow gut bleeding
- Chronic kidney disease — less erythropoietin once eGFR falls below about 45
- Anemia of chronic disease or inflammation — infection, autoimmune disease, cancer, heart failure
- Hypothyroidism, chronic liver disease, alcohol use disorder
- Inherited red cell disorders — thalassemia trait (small cells with normal ferritin), sickle cell disease, G6PD deficiency
- Medications — chemotherapy, methotrexate, zidovudine, some anticonvulsants and antibiotics
- Hemolysis — autoimmune, mechanical heart valves, some infections and drugs
- Bone-marrow disorders — myelodysplasia, aplastic anemia, leukemia, myeloma; usually with other counts abnormal
- Dilution — pregnancy, intravenous fluids, over-hydration
What symptoms go with low Hemoglobin?
- Often none when mild or slow to develop
- Fatigue, weakness, poor exercise tolerance, breathlessness on stairs
- Pale skin, lips or nail beds; a fast or pounding heartbeat; dizziness on standing
- Headaches, cold hands and feet, trouble concentrating
- Ice craving (pica) and restless legs with iron deficiency; numbness, tingling and unsteadiness with B12 deficiency
What do clinicians usually check next?
- Read the MCV and RDW on the same CBC: MCV under 80 fL points to iron deficiency or thalassemia trait, over 100 to B12, folate, alcohol, thyroid or liver causes, 80–100 to bleeding, chronic disease, kidney disease or the marrow
- Ferritin with iron, TIBC and transferrin saturation — ferritin under 30 ng/mL is iron deficiency; under 100 can still be deficiency when CRP is raised
- Vitamin B12 and folate when MCV is high, when there are nerve symptoms, or in anyone over 60, vegan, on metformin or acid suppressants
- Reticulocyte count — high means the marrow is responding to bleeding or hemolysis; low means under-production
- Metabolic panel (creatinine and eGFR; bilirubin and LDH for hemolysis), TSH, CRP, and a peripheral smear when the cause is unclear
- A stool blood test, and for men, post-menopausal women and anyone with gut symptoms, gastrointestinal evaluation — the source is in the gut until proven otherwise
- Hemoglobin electrophoresis when red cells are small but ferritin is normal, to identify thalassemia trait before anyone prescribes iron
Follow-up tests available at TestWell: TSH Test (Thyroid Stimulating Hormone) ($20.99), TSH with Reflex to Free T4 Test ($29.99), TSH + Free T4 Test ($27.99), Vitamin B12 Test ($19.99), Ferritin Test ($21.99), Transferrin Test ($23.99).
How do you recheck Hemoglobin?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Biological Age Panel | Panel · 3 tests | $59.99 | Yes | 1–3 business days |
| General Wellness Panel | Panel · 4 tests | $49.99 | Yes | 1–3 business days |
| Blood Clotting Panel | Panel · 4 tests | $149.99 | No | 3–7 business days |
| CBC with Differential Test | Test · 14 biomarkers | $17.99 | No | 1–3 business days |
Common questions
What hemoglobin level is anemia?
Below about 13.5 g/dL in men and 12.0 g/dL in non-pregnant women by most lab ranges (the WHO uses 13 and 12). Mild anemia still deserves a cause.
What is the most common cause of low hemoglobin?
Iron deficiency — from heavy periods in women of reproductive age and from slow gastrointestinal blood loss in men and older women. That is why ferritin is the first test added, and why iron deficiency in a man or post-menopausal woman leads to a gut evaluation rather than just iron tablets.
What hemoglobin level is dangerous?
Below about 8 g/dL most people are symptomatic and need same-day assessment; below 7 is the usual threshold for considering a transfusion, lower in young healthy people and higher in those with heart disease. How fast it fell matters as much as the number.
Is a hemoglobin of 11 serious?
It is mild anemia. On its own it is not dangerous, but it always has a cause worth finding — in most people iron deficiency — and the MCV and ferritin on the same draw usually point straight to it.
Can low hemoglobin cause hair loss or fatigue?
Fatigue, yes — it is the most common symptom, often before anything else is noticed. Hair shedding is more a feature of the iron deficiency that often underlies the anemia than of the hemoglobin level itself; both improve as iron is replaced, with hair lagging by months.
How do you raise hemoglobin?
By treating the cause. Iron deficiency corrects over 6–12 weeks of iron (oral, or intravenous when absorption is the problem) once the source of loss is addressed; B12 and folate deficiency respond within weeks; kidney-related anemia may need erythropoietin. Taking iron without a low ferritin can be harmful, so test first.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.