People normally have low levels of uric acid in their bloodstreams. The body produces uric acid when it breaks down purines, organic chemical compounds found naturally in foods and drinks. After digestion, uric acid enters the bloodstream to be processed by the kidneys and excreted in the urine.
When there is too much uric acid in the bloodstream it is called hyperuricemia, and it can lead to gout.
When Does Hyperuricemia Occur?
Uric acid levels in the blood naturally fluctuate, and what is considered a "normal" may vary depending on the lab doing the analysis. Typically, a person is considered hyperuricemic if he or she has more than 7.2 mg of uric acid per deciliter of blood.1
Uric acid levels get too high when:
- A person eats a diet high in purines
- The body produces too much uric acid (most often this has a genetic cause)
- The kidneys are not able to adequately filter and flush out uric acid from the blood stream (most common)
When hyperuricemia occurs, the excess uric acid can deposit in joints, where it can form uric acid crystals. These crystals cause joint irritation that produces pain and can spur an immune system response which then causes additional pain, swelling, redness and warmth. This painful joint inflammation is commonly referred to as a "flare."
Does Hyperuricemia Always Cause Gout?
It is possible to have hyperuricemia and not have gout: in fact, most people with hyperuricemia do not have gout symptoms. Experts do not fully understand what causes some people to develop gout symptoms while others do not.
While asymptomatic hyperuricemia does not need to be medically treated, some doctors consider it a sign that dietary and lifestyle changes should be made.
Hyperuricemia and kidney stones
When uric acid crystals form, they can collect in the kidney and cause kidney stones. (There are different types of kidney stones; uric acid stones are just one type.) Experts estimate that among people who have gout, nearly 14% report having had kidney stones.2
Pseudogout earned its name because its symptoms are similar to gout. Unlike gout, which is caused by uric acid crystals, pseudogout is caused by calcium phosphate crystals.
- Medline Plus. Uric Acid - Blood. US National Library of Medicine & National Institutes of Health. www.nlm.nih.gov Updated April 29, 2013. Accessed January 28, 2014.
- Kramer HM, Curhan G. The association between gout and nephrolithiasis: the National Health and Nutrition Examination Survey III, 1988-1994. Am J Kidney Dis. 2002 Jul;40(1):37-42. PubMed PMID: 12087559.