Understanding your blood results for dialysis & transplant patients
This leaflet has been written to help you to understand your blood results. It will explain the different types of basic blood tests used in renal & transplant medicine. It will tell you why the components of the blood that are tested are important to your body. You will find the normal levels for these blood tests listed on the last page.
Before we start, a warning - blood results in kidney patients are frequently not normal. Do not be alarmed by this. To understand your blood results better, you must talk to your doctor or nurse about them. They will help you to understand their meaning, not this leaflet!
1. FBC - full blood count
A full blood count provides your medical team with a range of information on the components of your blood. The four most significant are your white blood cell count, your haemoglobin level, your platelet count and ferritin.
- White cell count – there are 5 different types of white cells. They are part of the body’s defence systems against invading germs. A higher than normal count suggests that you have an infection caused by germs as the body releases more white cells to counter the threat caused by the invaders. A lower than normal count suggests that you are more at risk of infection.
- Haemoglobin – is a component of the red blood cells, which allows the red blood cells to carry oxygen from the lungs to the body’s tissues and carbon dioxide from the body’s tissues to the lungs.
- Platelets – are by comparison to red and white blood cells much smaller. Their job is to stop bleeding when damage occurs to small blood vessels, preventing blood from flowing into tissues and they play an important part in blood clotting processes after injury to larger vessels
- Ferritin – is a protein that stores iron in the body. Measurements of the amount of ferritin in the blood are used as an indication of the body’s need for iron including the need for treatment with iron therapy.
- Haematocrit or Packed Cell Volume (PCV) – is a measurement of the percentage of blood that is red blood cells. For example, in an average adult man every 100 mls of blood would consist of about 45 mls (0.45) of red blood cells and 55 mls of plasma. A high haematocrit can be an indication for venesection where the patient is bled deliberately in order to lose red blood cells.
2. Urea & Electrolytes (U & Es)
U & Es provide your medical team with an account of your basic blood chemistry, the different mixture of chemicals in the bloodstream. About 5 mls of blood are needed. The most important things measured are:
- Sodium - sodium is important in maintaining the balance of water in your body. It attracts water to it, binding with it. Too much sodium in the body and you will retain too much water in your body. In kidney failure, the damaged kidneys are unable to eliminate excess sodium leading to fluid retention. The symptoms of fluid retention are swollen ankles and extremities, raised blood pressure and increasing breathlessness as the heart comes under pressure from having to cope with pumping the extra fluid in the bloodstream around the body. It is also important, with potassium, in the conduction of messages in nerve fibres.
- Potassium – an important electrolyte, allowing nerve fibres to conduct messages and muscle cells to work normally. Maintaining potassium levels correctly is essential. Fluctuations in potassium levels can affect the heart causing abnormal heartbeats or even make it stop beating.
- Urea & creatinine – waste products from normal body processes turning food into energy in the cells of the body. When your kidneys fail you are unable to off-load these waste products and they build up in the body. Eventually, they are poisonous to the body and you will suffer the symptoms of ‘uraemia’. These include nausea, sickness, skin irritation, loss of appetite
Creatinine is used by doctors to assess the extent of kidney failure. It is a more reliable measure than urea. Creatinine may be measured in the blood but more accurate estimates of kidney function are obtained by measuring creatinine in the urine as well (a 24 hour urine collection for creatinine clearance).
3. Other tests
Other substances are measured in your blood which are important to renal patients. These are described below:
- Calcium – is vital for having good strong bones. It is also an important electrolyte, associated with the control of fluid in the body.
- Phosphate - a mineral that is also important in the maintenance of strong bones. Phosphate and calcium need to be in balance in the body. If phosphate levels in the blood become to high, the body strips calcium from the bones to balance things up in the blood, weakening the bones. In kidney failure, excess phosphate is not removed from the blood. Dialysis is unable to control phosphate levels easily. Therefore, calcium tablets may be given to you to bind with the phosphate in your food and stop it being absorbed into the body from the gut. This stops permanent damage being caused to your bones.
- Albumin – albumin is a protein found in the blood that helps to carry other materials in the bloodstream. For example, it can combine with fatty acids. These are concentrated sources of energy broken down from the food you eat and released into the bloodstream. When they combine with albumin they can be moved to cell tissues where they can be broken down and converted into energy to allow the cell to work properly.
Albumin is used by your medical team as an indicator for protein lost in the normal process of peritoneal dialysis. The dietitian often requests high protein diets for PD patients as a result. It is also a marker for poor nutritional status particularly in haemodialysis patients and is closely monitored by dietitians.
- Lipids – lipids are a group of molecules found in the in the body. Two important types of lipids are triglycerides and cholesterol. Triglycerides are the body’s most concentrated source of energy and cholesterol is important in the construction of cells and liver function. High levels of triglycerides and cholesterol are a risk factor for cardiovascular disease, although smoking and high blood pressure are more important. Low levels are a sign of poor food intake. It is difficult to give a normal range of results, particularly for cholesterol because lipids do vary according to factors such as age, weight and medical history.
4. INR - ‘International Normalised Ratio’
If you take the drug warfarin to prevent problems caused by blood clotting, you will have regular blood tests to check your INR. It is a measurement of the time that it takes for blood to clot. Your doctor will alter the dosage of warfarin according to the results of the test, as necessary.
When you first start warfarin, you will have your INR checked on an almost daily basis. As your results stabilise on a certain dosage, you will not need to have blood tests as frequently. Some people have checks once every one or two months.
Normal values - for blood tested at University of Hospital of Wales laboratories
These values give the statistical range that most healthy adult population will fall within when tested. As noted above, kidney patients will often find their blood results are not ‘normal’. This does not mean that they are bad. It is important to discuss your blood results with your doctor or nurse to understand what they mean to you as an individual.
- White blood cells 4-11 ´ 109
- Haemoglobin men 13-16.5 grams per decilitre (g/dl)
- women 11.5-15.5 g/dl
- Platelets 150-400 ´ 109
- Ferritin 15-300 micrograms per litre (m g/l)
- Haematocrit men 0.34-0.50
- (measured as index) women 0.30-0.48
- Sodium (Na) 133-144 millimoles per litre (mmol/l)
- Potassium (K) 3.4-5 mmol/l
- Urea 2.5-7.5 mmol/l
- Creatinine 70-120 mmol/l
- Calcium (Ca) 2.2-2.6 mmol/l
- Phosphate 0.8-1.45 mmol/l
- Albumin 35-50 grams per litre (g/l)
- Triglycerides 0.6–2.0 mmol/l
- Cholesterol no normal value available