A Normal Haemoglobin Level

A Normal Haemoglobin (Hb) Level

A normal haemoglobin level (often abbreviated as Hb) is essential for ensuring your body’s tissues receive enough oxygen. Because biological requirements differ, the standard reference ranges are separate for men and women.

Normal Haemoglobin Ranges

In the UK and many international regions, haemoglobin is measured in grams per litre (g/L).

Key Takeaway: A level of 120 g/L is considered normal for a woman, but would be classified as anaemia for a man.

What is Haemoglobin and Why Does It Matter?

Haemoglobin is an iron-rich protein found within your red blood cells. It performs two vital functions:

1. Oxygen Transport: It picks up oxygen in the lungs and delivers it to the rest of the body.
2. Waste Removal: It helps transport carbon dioxide back to the lungs to be exhaled.

Your Hb level is a direct reflection of your red blood cell count. A higher number typically indicates a higher concentration of red cells.

High vs. Low Haemoglobin Levels

When your Hb falls outside the normal range, it is categorised as follows:

• Anaemia (Low Hb): Your blood has too few red cells or too little haemoglobin, leading to tiredness and shortness of breath.
• Polycythaemia (High Hb): Your blood has a high concentration of red cells, which can make the blood thicker. This leads to a higher chance of blood clotting.

Understanding Cell Size: The MCV Test

To find the cause of anaemia, doctors look at the Mean Cell Volume (MCV), which measures the average size of your red blood cells.

• Normal MCV Range: 80 – 100 fL (femtolitres).

Classification of Anaemia by Cell Size

Anaemia is a clinical sign, not a final diagnosis. It is categorized by the size of the cells:

1. Microcytic (Small Cells – Low MCV): Most commonly caused by Iron Deficiency. In adults, this is often due to blood loss (such as gastrointestinal or uterine bleeding).
2. Normocytic (Normal Sized Cells – Normal MCV):
   • Haemolytic: Cells are destroyed too quickly (e.g. Sickle Cell, Thalassaemia).
   • Non-haemolytic: Often caused by chronic conditions, such as Chronic Kidney Disease (CKD).
3. Macrocytic (Large Cells – High MCV):
   • Megaloblastic: Often due to Vitamin B12 or Folate deficiency.
   • Non-megaloblastic: Can be caused by alcohol use or liver disease.

Other Resources

United Kingdom (UK)

• NICE CKS: Anaemia – Iron Deficiency
• British National Formulary (BNF): Treatment of Anaemias

United States (US)

• ASH: American Society of Hematology – Iron Deficiency
• Mayo Clinic: Haemoglobin Test and Ranges