Uric acid blood test: normal range explained

A uric acid test measures the amount of uric acid in a sample of your blood. Uric acid is a normal waste product that forms when the body breaks down purines, substances found in your own cells, especially as they die, and in some foods and drinks. The kidneys remove most uric acid in urine, so the blood level reflects both how much your body makes and how well the kidneys clear it.

Doctors order a blood uric acid test when someone has joint pain that might be gout, usually alongside a joint fluid test, and to follow uric acid levels during chemotherapy or radiotherapy, which release purines as cells break down. A 24-hour urine test, rather than the blood test, is used to find out whether uric acid is behind kidney stones. MedlinePlus says low blood levels are uncommon and usually not a problem.

Uric acid moves with food, drink, medicines, exercise and fluid balance as well as with the kidneys.

• Foods high in purines, such as red meat, organ meats and some seafood, raise uric acid, and so do fructose and alcohol of all types.
• Medicines such as diuretics, aspirin in small amounts, niacin, ciclosporin and tacrolimus raise it, while some blood pressure, cholesterol and gout medicines lower it. Tell your doctor what you take.
• Dehydration, fasting, a starvation diet and strenuous exercise all push the level up.
• Reduced kidney function lets uric acid build up, which your doctor considers with your kidney values.
• Some conditions, including an underactive thyroid, psoriasis, obesity and some blood disorders, raise it, and your doctor reads the result with them in mind.
• MedlinePlus suggests not eating or drinking for four hours before the test unless told otherwise, while Testing.com says fasting is not required; follow your lab's instructions.