Urate (uric acid)

Uric acid (urate) forms when the body breaks down purines, substances produced in our cells and obtained through food. This test shows the amount of uric acid in the blood and is most often performed for suspected gout or kidney stones, during gout treatment and as part of general check-ups.

Who the test is for

• people with sudden pain, swelling and redness of a joint, most often the big toe, when gout is suspected;
• people receiving urate-lowering medicines for gout;
• people with kidney stones and those having kidney function assessed, alongside creatinine and urea;
• patients being treated for leukaemia or lymphoma, when the breakdown of many cells can rapidly raise urate;
• people having a general check-up, alongside glucose, blood lipids and liver tests.

What uric acid is and what it indicates

Most uric acid is produced in the body, while a smaller amount comes from purine-rich foods such as offal, red meat and seafood. Most is excreted by the kidneys in urine and the rest through the intestines.

Blood levels rise when the body produces too much uric acid or the kidneys excrete too little. If urate remains elevated, it can accumulate as crystals in joints and tissues. This underlies gout, a painful joint inflammation, and crystals can also form stones in the urinary tract.

High uric acid (hyperuricaemia) is more common in people who are overweight or have high blood pressure, diabetes or impaired kidney function. However, many people with elevated urate never develop gout.

Preparation and sample

Uric acid is measured in venous blood. Fasting is not essential for the test alone, but blood is often taken in the morning alongside tests requiring fasting, such as glucose and blood lipids.

The day before sampling, avoid a large meal rich in meat or offal, alcohol and exhausting exercise, because these can temporarily raise urate. Tell your doctor which medicines and supplements you take: diuretics, low-dose acetylsalicylic acid and niacin (vitamin B3) can raise urate, while gout medicines lower it. Do not stop medicines without medical agreement.

If a doctor requests urine uric acid, for example when investigating kidney stones, urine collected over 24 hours is required.

How results are interpreted

Uric acid is expressed in µmol/L. The reference interval depends on sex, age and method and is printed on the report; values in women before menopause are generally lower than in men. A doctor interprets the result alongside symptoms, kidney function and your medicines.

High urate

The most common causes of high uric acid are:

• a diet rich in meat, offal and seafood, alcohol, particularly beer, and fructose-sweetened drinks;
• excess body weight and metabolic syndrome;
• impaired kidney function and medicines that reduce urate excretion, particularly diuretics;
• increased cell breakdown, for example in some blood diseases, extensive psoriasis or during chemotherapy;
• fasting, dehydration and very intense physical exertion.

High urate alone is not a diagnosis of gout. Gout is recognised through symptoms and joint examination and, when possible, confirmed by finding crystals in joint fluid. High urate without symptoms is usually not treated with medicines; a doctor instead advises dietary and lifestyle changes and assesses blood pressure, glucose, blood lipids and kidney function.

Urate in gout

During an acute gout attack, urate can be normal. British NICE guidelines therefore advise that if the result during an attack is below 360 µmol/L but gout remains suspected, testing should be repeated at least two weeks after the attack resolves.

With urate-lowering medicines, the usual target is below 360 µmol/L. If uric acid nodules under the skin (tophi) are present or attacks continue, a doctor may set a lower target, below 300 µmol/L. Urate is checked more often while the dose is adjusted and less frequently once the target is reached.

Low urate

Low urate is rarely clinically significant. It is most often due to urate-lowering medicines, and levels are also lower in the first half of pregnancy. Less often, it accompanies severe liver disease or kidney tubular disorders, which a doctor assesses using other findings.

How to arrange testing

You can have blood taken without an appointment or referral at one of our branches across Croatia (listed on the Contact page). Prices for all tests and panels are available in the service price list. Uric acid is included in the Extended Preventive Panel, which also includes, among other tests, blood count, glucose, blood lipids, liver tests, urea and creatinine. Because of the glucose and lipids, arrive fasting for blood sampling for this panel.

Frequently asked questions

Can my uric acid be normal even if I have gout?

Yes, particularly during an attack, when urate temporarily falls in some patients. A doctor then repeats testing after inflammation resolves. Symptoms, joint examination and, when possible, joint fluid examination are decisive for diagnosis.

What should I eat if my uric acid is high?

A balanced diet with less offal, red meat and seafood, less alcohol, particularly beer, and fewer sweetened drinks and fructose-containing juices is usually recommended. Gradual loss of excess weight also helps. Diet lowers urate only moderately, so in gout with recurrent attacks a doctor usually also recommends medication.

Is high uric acid dangerous if I have no symptoms?

It does not cause symptoms by itself, and most people with mildly elevated urate never develop gout. However, it often accompanies high blood pressure, diabetes, high blood lipids and reduced kidney function, making it a useful reason for a doctor to assess these factors too.

What do amorphous urates in urine mean?

Amorphous urates are small collections of uric acid salts visible in urine sediment. They most often form in concentrated, acidic urine or when a sample cools, so usually have no special significance and do not indicate blood uric acid levels. Read more about this test in the article on urinalysis: dipstick and sediment.