Haematocrit

What it is

Haematocrit, often abbreviated as Hct, is a simple blood test that measures the proportion of your blood volume that is made up of red blood cells. Think of your blood as being made up of different components: red blood cells, white blood cells, platelets, and plasma (the liquid part). Haematocrit tells us what percentage of that total volume is taken up by red blood cells.

In the UK, the typical reference range for haematocrit in adults is generally between 0.4 and 0.54 litres per litre (l/l). This means that for every litre of blood, between 0.4 and 0.54 litres should be red blood cells. This can vary slightly between laboratories, and your GP will interpret your results in the context of your individual health.

Why it matters

Red blood cells are the workhorses of your circulatory system. Their primary job is to carry oxygen from your lungs to all the tissues and organs in your body, and to carry carbon dioxide back to the lungs to be exhaled. This oxygen delivery is vital for your body to function correctly, providing energy for everything from thinking to moving.

The haematocrit level gives doctors a good indication of how effectively your blood can carry oxygen. A haematocrit that is too high or too low can suggest that something might be affecting your body's ability to produce red blood cells, or that there's an issue with how they are being used or lost. It’s a key part of a Full Blood Count (FBC), which is a very common and informative blood test.

What can cause it to be high or low

Several factors can influence your haematocrit level.

Higher than normal haematocrit (high Hct) can sometimes be seen in situations where your body is trying to compensate for a lack of oxygen. This can include living at high altitudes, where the air has less oxygen. It can also be a response to certain lung diseases or heart conditions that affect oxygen levels. Dehydration is another common cause of a high haematocrit, as the plasma volume decreases, making the red blood cells appear to make up a larger proportion of the blood. Certain kidney tumours and genetic conditions can also lead to an increase in red blood cell production.

Lower than normal haematocrit (low Hct) is often associated with anaemia, a condition where the body doesn't have enough healthy red blood cells. This can happen for a number of reasons. Blood loss, whether from heavy periods, internal bleeding, or injury, can reduce the number of red blood cells. Nutritional deficiencies, particularly a lack of iron, vitamin B12, or folate, can impair the body's ability to produce red blood cells. Chronic diseases, such as kidney disease or inflammatory conditions, can also affect red blood cell production. Bone marrow disorders, where the body's red blood cell factory isn't working properly, can also result in a low haematocrit.

Lifestyle factors that may help

While your haematocrit is primarily influenced by underlying medical conditions, certain lifestyle choices can play a supportive role in maintaining healthy blood cell production and overall well-being.

• Balanced Diet: Ensuring your diet is rich in essential nutrients is important. Foods containing iron (like lean red meat, leafy green vegetables, and fortified cereals), vitamin B12 (found in animal products like meat, fish, and dairy), and folate (present in green leafy vegetables, beans, and fortified grains) are crucial for red blood cell formation. Discussing your dietary intake with a healthcare professional can help identify any potential gaps.
• Hydration: Staying adequately hydrated is important for maintaining a normal blood volume. Drinking enough fluids throughout the day helps ensure that your blood components are in the correct proportion.
• Regular Exercise: Moderate, regular physical activity can support overall cardiovascular health and circulation. However, the type and intensity of exercise should be considered, especially if you have any existing health conditions.

Questions to discuss with your GP

If your haematocrit results are outside the typical reference range, or if you have concerns about your blood count, it's always best to have a conversation with your GP. Here are some questions you might consider discussing:

• What does my specific haematocrit result mean in the context of my overall health?
• Are there any other tests that might be helpful to understand why my haematocrit is high or low?
• Could my current medications or any recent illnesses be affecting my haematocrit level?
• What are the potential long-term implications of my haematocrit result?
• Are there any specific dietary adjustments or lifestyle changes you would recommend for me to consider?
• What signs or symptoms should I be aware of that might indicate a need for further medical attention?