What should you know about rdw blood test?

Red blood cells carry oxygen and normally have a relatively consistent size. RDW describes the spread of cell sizes in the sample. A result outside the laboratory range is a clue, not a diagnosis. The meaning changes according to haemoglobin, mean cell volume, iron-related results, vitamin levels and your symptoms. Variation can occur when the body is making new cells alongside older ones, or when red-cell production is affected by a nutrient problem, inflammation or another illness. A single value cannot identify the cause on its own.

Review the complete report with a clinician rather than comparing the value with an online range. Mention tiredness, breathlessness, heavy menstrual bleeding, digestive symptoms, dietary restrictions, recent infection and long-term conditions. Depending on the pattern, the clinician may check iron, vitamin B12, folate, kidney function or signs of inflammation. Do not start iron or other supplements without advice, because treatment should match the underlying reason.

Arrange medical review if an abnormal RDW accompanies worsening fatigue, breathlessness, fainting, palpitations, unusual bleeding, black stools or persistent digestive symptoms. Seek emergency care for severe breathlessness, chest pain, collapse or confusion. The test result itself is not an emergency, but symptoms can require rapid assessment.

Which parts of my full blood count change the interpretation of RDW? Could iron, vitamin deficiency, kidney disease or inflammation be relevant? Do I need repeat testing or additional blood tests?