What is RDW in a Blood Test?
A red cell distribution width (RDW) test measures the differences in the volume and size of your red blood cells. Red blood cells carry oxygen from your lungs to every cell in your body, so any abnormalities in red blood cells can disrupt your body’s ability to deliver oxygen to your cells.
Normally, red blood cells are about the same size, but some conditions, like anaemia, can cause increased variation in their size. These variations can be measured as part of a Blood Health Profile test, which includes an RDW blood test as standard.
In this article, we explain in more detail what a red blood cell distribution width test is, how it can help diagnose certain medical conditions, and how healthcare professionals interpret the results.
What is an RDW (red blood cell distribution width) blood test?
An RDW, or red blood cell distribution width test measures the difference in volume and size of red blood cells. Red blood cells play a vital role in delivering oxygen from your lungs to all the cells in your body. Abnormalities in your red blood cell distribution width can interfere with the normal delivery of oxygen and cause health complications.
Although the name suggests that the width of your red blood cells is measured, this is incorrect. Cell distribution width refers to the distance between the cell sizes in a blood sample as plotted on a type of graph known as a histogram. Similar values indicate the same cell size and that your RDW value is low. Different values, indicating varied cell sizes, are spread out on a histogram and can demonstrate your RDW value is high.
If you have high RDW levels, it can mean that you have a nutrient deficiency, anaemia, or another medical condition.
A RDW blood test is included in a Blood Health Profile blood test, a test that analyses different aspects of your blood. This is because RDW blood test results alone cannot provide conclusive insights into the root cause of any problems with your red blood cells, and further insights from the analysis of other cells are usually required to help a doctor make a diagnosis.
When would an RDW blood test be needed?
A full Blood Health Profile test, which includes a RDW blood test, is often carried out as part of a routine check of your overall health, but can also be beneficial if you have experienced:
- Symptoms of anaemia – this can include weakness, dizziness, pale skin, and cold hands and feet
- A family history of thalassemia, sickle cell anaemia, or another inherited blood disorder
- A chronic illness, like Chrohn’s disease, or HIV/AIDS
- A diet deficient in iron and other essential minerals
- A long-term infection or repeated infections in a short space of time
- Excessive blood loss from an injury or surgical procedure
Symptoms
As anaemia is one of the most common reasons people have an RDW blood test, it is important you are aware of the symptoms of this condition. They can include:
- Fatigue
- Shortness of breath
- Feeling cold
- Dizziness
- Feeling weak
- Unusually pale or dry skin
- Frequent headaches
Conditions
An RDW blood test along with other blood tests commonly included as part of a Blood Health Profile test can be used to help diagnose anaemia and its root cause. Conditions commonly associated with anaemia include:
- Cancer
- Cardiovascular disease
- Kidney disease
- Liver disease
- Thalassemia
- Chronic diseases, like Crohn’s disease or diabetes
- Vitamin and mineral deficiencies
- Long-lasting infection
- Significant loss of blood from an injury or surgery
How are the RDW results interpreted?
Although an RDW blood test is a useful way to measure your red blood cell distribution width, it is rarely used on its own to provide a diagnosis of a medical condition, such as anaemia. That’s because other blood tests included as part of a Blood Health Profile test help build a better picture of any abnormalities and their underlying cause.
However, an RDW blood test can offer useful insights into the variation in size of your red blood cells and show if you have high, low, or normal RDW levels.
High RDW levels
Elevated RDW blood test results mean that there is variation in the size of your red blood cells above what is considered ‘normal’. High RDW levels can be a sign of anaemia or a related condition. Usually, the result of your RDW blood test will be reviewed alongside other blood tests included as part of a Blood Health Profile test, like your average red blood cell size or MCV, to help healthcare professionals assess the health of your red blood cells.
Low RDW levels
Low RDW levels are not normally a cause for concern and aren’t associated with any particular types of anaemia.
Normal RDW levels
An RDW blood test normal range means that your red blood cells are similar in size. Your Results Report will highlight what is considered a normal range, flag if your results fall outside of this and indicate any necessary follow-up required.
Is there any risk to a RDW blood test?
An RDW blood test is a standard blood test and has very little risk of side effects. You may experience a sharp scratch when the needle is inserted and some bruising at the site where blood is taken, but this will fade within a few days.
Some people experience lightheadedness after having their blood taken, but the effects are only temporary and usually clear quickly. If you know you tend to feel faint after having a blood test, let your health assessment specialist know beforehand, and they can help you manage feelings of lightheadedness by encouraging you to rest for a few moments after the test and get up slowly when you feel ready.
How can I check my RDW levels?
It’s easy to check your RDW levels as an RDW blood test is a standard part of our Blood Health Profile test. A Blood Health Profile test analyses different cells in your blood to provide information about your general health and help diagnose conditions like anaemia.
A trained health assessment specialist will use a small needle to take a blood sample from a vein in your arm. Once the needle is inserted, a small amount of blood is collected into a test tube, which is then sent to a lab for testing. Appointments can be booked at locations across the UK at a time and date to suit you, making it a quick, easy, and convenient way to gain insights into your RDW levels.
A Blood Health Profile test is a useful tool for providing vital insights into your overall health so is included as standard in many of our full-body health assessment packages. Our full body health checks also include key metrics like your blood pressure and weight as well as your risk of some common medical conditions, like diabetes to give you a better picture of your general health.
With all our tests, we use the latest technologies to ensure accurate results. In addition, you get a comprehensive Results Report and free access to a 24/7 GP helpline for a year for complete peace of mind following your health assessment.
