Doctor's Assessment Included
Every result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
Haematocrit: Normal Values and What a High Result Means
Hematocrit monitoring becomes increasingly valuable with age, as changes in blood composition can affect energy levels, cognitive function, and overall well-being. Regular testing supports the early detection of anemia and dehydration, common concerns in seniors.
Results within 1–3 working days after your blood draw (estimate)
What It Measures
Haematocrit indicates what proportion of your blood consists of red blood cells. Blood is broadly made up of fluid (plasma) and cells; haematocrit is the share taken up by the red cells, often reported as l/l or as a percentage.
The value is measured as standard in the complete blood count and tracks closely with your haemoglobin and red cell count.
Because haematocrit is a ratio rather than an absolute amount, it is strongly influenced by your fluid balance. Dehydration shrinks the plasma fraction and therefore raises the haematocrit, without you having produced any more red blood cells.
Why It Matters
A low haematocrit fits anaemia: there are too few red blood cells to carry enough oxygen. The causes run parallel to those of a low haemoglobin: iron deficiency, blood loss, a lack of vitamin B12 or folate, a chronic illness or reduced kidney function.
A high haematocrit means your blood is thicker and more viscous. Dehydration is the most common, and usually harmless, explanation. Smoking, sleep apnoea, time at high altitude and a bone marrow disorder can genuinely increase red cell production.
Testosterone therapy also raises the haematocrit. For that reason the value is checked as standard during TRT: when the blood becomes too thick the risk of clot formation increases and the dose may need to be adjusted.
When to Test
Haematocrit is measured as standard in the complete blood count, for example for fatigue, pallor or breathlessness on exertion.
The value is also important to follow during testosterone therapy, because that can raise the haematocrit. It is relevant for endurance athletes too, since blood that is too thick can actually impede flow.
Make sure you are well hydrated at the time of the blood draw and test at rest where possible. Dehydration or hard exertion shortly before the measurement can artificially raise the haematocrit and lead to a wrong conclusion.
Symptoms
Low Levels
High Levels
Lifestyle Tips
Drink enough, certainly on the day of the blood draw. Dehydration is by far the most common reason for an apparently raised haematocrit.
Stopping smoking lowers a structurally raised haematocrit, because your body then needs to make fewer red cells to achieve the same oxygen transport.
If you use testosterone, have your haematocrit checked as agreed. A persistently high value calls for a discussion with your doctor about dosing or other measures; do not experiment with this yourself.