Sugar and metabolism
Urinezuur
A waste product from the breakdown of purines; at a high value, crystals can form that cause gout or kidney stones.
Everything about this testWhat it measures
Uric acid is formed during the breakdown of purines, substances found in body cells and in food, for example in meat, fish and beer. Most uric acid leaves the body via the kidneys in the urine, and part via the gut. If the body makes a lot of uric acid or the kidneys excrete too little, the value in the blood rises. At a high value, uric acid can form crystals in joints, under the skin or in the kidneys.
- Raised uric acid (hyperuricemia), the most important risk factor for gout
- Monitoring of uric acid lowering treatment in gout
- Increased chance of uric acid stones in the kidneys
High
A raised uric acid does not mean that you have gout. According to Thuisarts, about 1 in 10 people with a lot of uric acid in the blood develop gout; most people with a high value therefore never get symptoms. A high value is more common in men, with overweight, a lot of alcohol (especially beer), a lot of meat or fish, sugary soft drinks and reduced kidney function. Diuretics (including hydrochlorothiazide and furosemide) and a low dose of acetylsalicylic acid also raise uric acid. Gout itself causes a sudden, very painful, red and swollen inflammation of a joint, usually of the big toe. Rarely, a strongly raised value fits a rapid breakdown of cells in a blood disease or a hereditary metabolic disease.
Low
According to the Dutch Society for Clinical Chemistry (NVKC), a low uric acid is much less common and is rarely a cause for concern. It occurs with the use of uric acid lowering medicines (such as allopurinol) and during pregnancy. Rarely, a low value is linked to a liver or kidney disease or a hereditary metabolic disease; the test is not suitable for showing these.
If your result is abnormal
With a raised uric acid without symptoms, the GP usually gives general lifestyle advice at most, such as less alcohol and losing weight if overweight, and looks at medicines, kidney function and risk factors for cardiovascular disease. With symptoms of gout, the GP assesses the joint according to the Dutch GP guideline (NHG) on arthritis and repeats the uric acid a few weeks after the attack. If the diagnosis is in doubt, referral for examination of joint fluid follows.
Reliability
Uric acid weighs the chance of gout, but does not make a diagnosis. According to the Dutch Society for Clinical Chemistry (NVKC), the test is not specific for gout and a raised value leads to symptoms in only a limited share of people. According to the Dutch GP guideline (NHG) on arthritis, gout is mainly diagnosed based on the symptoms and examination of the joint; during an attack, uric acid can even be normal. In people with gout who use uric acid lowering medicines, the value is a good measure of the treatment: the FMS guideline names a target value below 0.36 mmol/l.
Limitations
- Alcohol, a purine-rich meal, fasting, dehydration and heavy exertion temporarily raise the value.
- Diuretics and a low dose of acetylsalicylic acid raise uric acid; losartan, fenofibrate and uric acid lowering medicines lower it.
- During or just after a gout attack, the value can be normal while there is still gout.
- Men have higher normal values than women; after menopause, uric acid rises in women.
How common is this
Gout is the most common inflammatory rheumatic disease in the Netherlands: according to the Dutch medical specialists' guideline (FMS), based on RIVM figures, about 480,000 people had gout in 2017. Gout is much more common in men, especially over the age of 40, and in women mainly after menopause. A raised uric acid without symptoms is more common than gout, because most people with a high value never have an attack.
Who is this useful for
The result is most meaningful with symptoms that fit gout, such as a suddenly painful, red and swollen joint, in known gout to monitor treatment, and with kidney stones. Uric acid can also be measured with reduced kidney function. In people without symptoms, a raised value says little: most people with a high value never get gout, and a raised value without symptoms is generally not treated.
Downsides and risks
- A raised uric acid without symptoms can wrongly give the idea that you have or will get gout.
- A normal value during an attack can give false reassurance.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results