Haemoglobin
Hb
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Category
Blood
Sample
Blood
Report Time
1 hr
Fasting
Not needed
About Haemoglobin
Hemoglobin (Hb) is the iron-rich protein inside red blood cells that picks up oxygen in the lungs and delivers it to every tissue in the body. It is also what gives blood its red colour. A hemoglobin test measures how much of this protein is in a given volume of blood, and it is the single most important number used to diagnose anaemia.
When hemoglobin is low, the body gets less oxygen than it needs, which can cause tiredness, breathlessness, paleness, dizziness, headaches and a racing heart. Anaemia is extremely common in India, especially among women, adolescent girls, pregnant women and young children, and iron deficiency is the leading cause. When hemoglobin is high, the blood can become thicker, and doctors look for causes such as dehydration, smoking, living at high altitude, or conditions that make the bone marrow produce too many red cells.
Hemoglobin is measured as part of a complete blood count (CBC), but it can also be tested on its own as a quick, low-cost check. Results are reported in grams per decilitre (g/dL). A single reading is a starting point: your doctor will look at your red cell indices, such as MCV, along with symptoms to find out why the level is low or high.
When Should You Get This Test?
A hemoglobin test is useful for:
- Symptoms of anaemia — tiredness, weakness, pale skin, dizziness, breathlessness on exertion, headaches, cold hands and feet, brittle nails or hair fall.
- Routine health check-ups, especially for women of childbearing age and adolescents.
- Every stage of pregnancy — usually at the first visit and repeated in the second and third trimesters.
- Heavy or prolonged periods, or any source of ongoing blood loss, such as piles or stomach ulcers.
- Before surgery or blood donation.
- Monitoring people with chronic kidney disease, cancer, long-term inflammatory disease or those on iron, vitamin B12 or folic acid treatment.
- Assessing the nutrition and growth of infants and children.
- Living or working at high altitude, or smoking heavily, when high hemoglobin is suspected.
Conditions This Test Can Detect
An abnormal hemoglobin may point to:
- Low hemoglobin (anaemia): iron deficiency, vitamin B12 or folate deficiency, chronic blood loss, thalassaemia or sickle cell disease, chronic kidney disease, long-standing infection or inflammation, hookworm infection, and bone marrow problems.
- High hemoglobin: dehydration, smoking, chronic lung disease, living at altitude, sleep apnoea, certain medicines such as testosterone, and polycythaemia vera, a rare bone marrow condition.
The cause is found with follow-up tests such as MCV and other red cell indices, serum ferritin, iron studies, vitamin B12 and folate levels, and, where appropriate, a peripheral blood smear or hemoglobin electrophoresis.
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How to Prepare
- No fasting is needed for a hemoglobin test alone. If it is part of a larger panel with blood sugar or lipids, the lab may ask you to fast for 8–12 hours.
- Drink water normally. Being very dehydrated can falsely raise hemoglobin, while being overhydrated can slightly lower it.
- Tell your doctor if you recently had a blood transfusion, are pregnant, or have been bleeding.
- Avoid taking iron tablets just before the sample if your doctor has advised a baseline test; otherwise continue medicines as prescribed.
Normal Reference Ranges
Normal values vary with age, sex, pregnancy and altitude, and slightly between labs. Typical ranges are:
| Group | Typical hemoglobin (g/dL) |
|---|---|
| Adult men | 13.5 – 17.5 |
| Adult women (non-pregnant) | 12.0 – 15.5 |
| Pregnant women | 11.0 or above (below 11 is anaemia; below 7 is severe) |
| Children 6 months – 5 years | 11.0 or above |
| Children 5 – 12 years | 11.5 or above |
| Newborns | 14.0 – 24.0 (falls over the first weeks) |
The World Health Organization classifies anaemia as mild, moderate or severe depending on how far hemoglobin falls below these cut-offs. Your doctor decides on treatment based on the cause, not the number alone.
Further reading: MedlinePlus – Lab tests, Mayo Clinic – Tests & procedures, Cleveland Clinic – Diagnostics, Lab Tests Online. Values are approximate and may vary by laboratory; this page is general information, not medical advice.
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Frequently Asked Questions
What is a normal hemoglobin level for women?
For adult non-pregnant women, about 12.0–15.5 g/dL is considered normal. In pregnancy, 11.0 g/dL or above is the usual target.
How can I increase my hemoglobin?
It depends on the cause. For iron deficiency, doctors usually prescribe iron tablets and advise iron-rich foods such as leafy greens, pulses, jaggery, dates, dried fruit and, for non-vegetarians, meat and fish, along with vitamin C to improve absorption. Vitamin B12 or folate deficiency needs those supplements. Don't self-medicate with high-dose iron without a test, since not all anaemia is due to iron deficiency.
Do I need to fast before a hemoglobin test?
No, not for hemoglobin alone. Fasting is only needed if other tests like blood sugar or a lipid profile are done at the same time.
What symptoms suggest low hemoglobin?
Persistent tiredness, pale skin, dizziness, breathlessness on climbing stairs, palpitations, headaches, cold extremities and poor concentration. Severe anaemia can cause chest pain or fainting and needs urgent care.
Can dehydration affect my hemoglobin result?
Yes. Dehydration concentrates the blood and can make hemoglobin look falsely high, so drink water normally before the test.
How often should hemoglobin be checked in pregnancy?
Usually at the first antenatal visit and again in the second and third trimesters, and more often if anaemia is found.
Is hemoglobin the same as a CBC?
No. Hemoglobin is one measurement within a complete blood count, which also includes white cells, platelets and red cell indices. A CBC gives a fuller picture, which helps find the cause of anaemia.
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Medical Disclaimer: This page is for informational purposes only and does not constitute medical advice. Lab test results should always be interpreted by a qualified healthcare professional in the context of your clinical history. Do not self-diagnose or alter your treatment based on test results alone.
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