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Haemoglobin

The amount of haemoglobin in a volume of blood. Haemoglobin is the iron-containing protein inside red blood cells that binds oxygen in the lungs and releases it in the tissues, so the figure is a proxy for how much oxygen the blood can carry. It is measured on almost every full blood count and is usually reported next to haematocrit, red cell count and the red cell indices (MCV, MCH), which together say more than haemoglobin alone.

General information only — not a diagnosis, not treatment and not a substitute for your doctor. Reference ranges differ between laboratories, so the range printed on your own report is the one that counts, and only a clinician who knows your history can say what a result means for you. Never start, stop or change a medicine or supplement based on this page.

Usual adult reference range

The ranges below are typical adult reference intervals. Your own laboratory sets its own, printed next to your result, and that is the one to compare against.

Source: Typical adult reference interval published by clinical laboratories; intervals are sex-specific and differ between laboratories. · checked 2026-09-02

What a high result generally indicates

A raised haemoglobin most often reflects concentration rather than production: dehydration shrinks the plasma volume and the same red cells look denser. Living at altitude, smoking and chronic lung disease raise it for a physiological reason — less available oxygen. A persistently high value with no such explanation is investigated further.

What a low result generally indicates

A low haemoglobin is anaemia. It is a finding, not a diagnosis: iron deficiency, B12 or folate deficiency, blood loss, chronic inflammation, kidney disease and several inherited conditions all produce it, and the red cell size (MCV) is usually the first clue to which. Symptoms, when present, are tiredness, breathlessness on exertion, pallor and palpitations.

These are general patterns, not a diagnosis. Many things cause a high or low result, and the same figure means different things in different people. What yours means is a question for the doctor who ordered the test.

What affects this result

• Hydration — a dehydrated sample reads higher, an over-hydrated one lower.
• Altitude — people living high above sea level run higher haemoglobin.
• Smoking raises it; carbon monoxide reduces the oxygen each cell carries.
• Menstruation and pregnancy both lower it, pregnancy partly by dilution.
• Posture and tourniquet time can shift a result by a few per cent.
• Endurance training can lower it slightly by expanding plasma volume.

Before the test

No fasting needed. Hydration status matters more than food.

Any preparation instruction that comes with your test slip overrides this general note — follow the one your clinician or laboratory gave you.

The one thing to take from this page

The range above is a typical interval for orientation. Your own laboratory's range, printed beside your result, is the one that applies to you — and a result is only meaningful alongside your symptoms, your history, your medicines and your other tests. That reading is a clinician's job. This page cannot diagnose anything, cannot tell you to change a medicine or a supplement, and is not a substitute for the person who ordered your test.

Frequently asked questions

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