Full blood count (FBC / CBC)
Haemoglobin blood test: what a high or low result means
What a haemoglobin (Hb) result measures, what a low or high level can mean, and what to ask your doctor.
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Explain my results → Available on web, iOS & Android.What is haemoglobin?
Haemoglobin is the protein inside your red blood cells that carries oxygen from your lungs to the rest of your body, and it is what gives blood its red colour. It is measured as part of a full blood count (FBC), called a complete blood count (CBC) in the US. On your results it may appear as Hb or Hgb, and in the US it is spelled hemoglobin.
Why is this test done?
- To check for anaemia if you feel tired, breathless or look pale
- As part of a routine health check or before an operation
- To monitor a long-term condition, such as kidney disease, or a treatment that can affect your blood
- To follow up a previous result that was outside the range
What does a high haemoglobin mean?
A high haemoglobin means there is more oxygen-carrying protein in your blood than usual. It is less common than a low result and is often mild.
Possible reasons include:
- Dehydration, which concentrates the blood
- Smoking
- Living at high altitude
- Long-term lung or heart conditions that lower oxygen levels
- Less commonly, a bone marrow condition that makes too many red cells
What does a low haemoglobin mean?
A low haemoglobin is called anaemia. It can make you feel tired, weak or short of breath, although a mild drop may cause no symptoms at all.
Possible reasons include:
- Iron deficiency, for example from heavy periods, pregnancy, diet or slow bleeding from the gut
- Low vitamin B12 or folate
- Blood loss
- Long-term conditions such as kidney disease or inflammatory conditions
- Pregnancy, when the blood naturally becomes more diluted
Why we don't list a "normal range". Reference ranges differ between laboratories and can depend on your age, sex and whether you are pregnant. The range printed next to your result on your own report is the one that applies to you, so use that, and talk to your doctor about what your result means for you.
What can affect your haemoglobin result?
- Your sex and age, which is why labs use different ranges for men, women and children
- Pregnancy
- Recent blood loss or a recent blood transfusion
- How well hydrated you were when the sample was taken
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Results are easier to understand together. Patiently AI explains your report as a whole and writes personalised questions for your next appointment.
Try it with your own results → Paste, upload or photograph your results.Questions to ask your doctor
- Is my haemoglobin low enough to explain how I have been feeling?
- If I have iron deficiency without an obvious cause, do I need stomach or bowel tests?
- Do I need other tests, such as ferritin, vitamin B12 or folate, to find the cause?
- Should I take iron or any other supplement, and for how long?
- When should my blood be checked again?
Frequently asked questions
Is low haemoglobin the same as anaemia?
Yes. Anaemia means your haemoglobin is lower than the range for your age and sex. Anaemia is a finding rather than a diagnosis in itself, so the next step is usually to find out why it is low, often with iron, vitamin B12 and folate tests.
What is the difference between Hb and Hgb?
None. Both are abbreviations for haemoglobin. Different labs and countries simply use different short forms.
Can I raise my haemoglobin with diet?
If the cause is iron deficiency, iron-rich foods can help, but a doctor may also recommend iron tablets. Diet alone will not fix anaemia with another cause, which is why finding the cause matters.
Can Patiently AI explain my haemoglobin result?
Yes. Paste your results, or upload a photo, PDF or Word file, and Patiently AI explains them in plain English, sticking to the numbers and ranges on your own report rather than adding its own, and suggests questions to ask your doctor. It is free, needs no account, and removes identifying details on your device first.