High uric acid: causes, gout and what you can influence yourself

Many people know this pattern. Your lab report lists uric acid, with an asterisk next to it. You have no pain, no swollen joint, nothing.

And still, it nags at you. Are you no longer allowed a beer, a steak? Is the apple juice in the morning suddenly a problem?

Or the other way round: you woke up at night because even the duvet on your big toe hurt. And your uric acid was normal.

Both situations become easier to understand once you keep three things apart: the lab value, the crystals and the disease called gout.

What uric acid is and why your body does not simply break it down

Your body breaks down and rebuilds cells every day. Every cell contains genetic material, and that genetic material contains building blocks called purines. Purines also come in with food, especially with meat, organ meats and seafood.

When purines are broken down, a small molecule sits at the end of the chain: uric acid. The enzyme that handles the step just before it is called xanthine oxidase. Incidentally, this is exactly where allopurinol and febuxostat act later on.

In most mammals, the process continues. An enzyme called uricase breaks uric acid down into a highly soluble substance that leaves easily with the urine. In humans, this station is missing.

Lab Why evolution arranged things this way remains open. A laboratory study around Kratzer reconstructed the uricase enzymes of extinct mammalian ancestors: their activity declined step by step until the gene fell silent in the great apes. The idea that this loss helped convert fructose into fat more quickly is a hypothesis from cell experiments and not evidence in humans.

Waste product or protective substance? Both are discussed

Uric acid has a bad reputation. Yet as early as 1981, Ames and colleagues showed in laboratory experiments with red blood cells that urate can scavenge oxygen radicals, in these experiments roughly as effectively as vitamin C. This gave rise to the hypothesis that uric acid is one of the most important antioxidants in the blood, a hypothesis from the test tube.

A working group around Nakayama goes one step further in a review and writes that the notion "the lower, the better" is not correct. Values that are too high and values that are too low can both cause problems.

The solubility limit: when dissolved suddenly turns solid

As long as uric acid floats dissolved in the blood, you feel nothing. It becomes a problem when it precipitates as a sodium salt, monosodium urate. Under the microscope, these crystals look like tiny needles.

In its diagnostics chapter, the German S3 guideline on gout gives a solubility product of approx. 6.8 to 7 mg/dl, and in its therapy chapter, for body conditions of pH 7.4 and 37 °C, up to approx. 6.5 mg/dl. With cold, poor circulation and in tissue already damaged by osteoarthritis, the limit is lower. That is why it is better to speak of a zone around 6.8 mg/dl than of a sharp cut-off.

Around 70 percent of uric acid leaves the body via the kidneys, the rest mainly via the gut. How fructose is processed in the liver and why uric acid can also be produced in the process is explained in detail in Sugar and fructose: the liver is where it happens. Here, the focus is on what happens to uric acid afterwards.

And now you know why one and the same substance can remain invisible in the blood and trigger severe pain in a joint.

Uric acid level: why there is no single normal value for everyone

Put two reports from two laboratories side by side. It is quite possible that uric acid comes with two different reference ranges, one in green, one with an asterisk.

That is not a mistake. The German general practice guideline on acute gout states that the reference ranges for serum uric acid given by individual laboratories differ considerably. That is why you deliberately will not find a table of normal values here.

Two different questions: statistics and physics

A reference range describes which values are common in a comparison group. It depends on that comparison group and on the measurement method, and it tells you what is usual. The solubility limit says something else: the point at which uric acid can crystallize under body conditions. A value can therefore be statistically unremarkable and still lie in the zone where crystals can form. The American College of Rheumatology guideline uses the same order of magnitude for asymptomatic hyperuricemia: uric acid above 6.8 mg/dl without previous gout attacks and without gout nodules under the skin.

A word on units: some laboratories report mg/dl, others µmol/l. The NICE guideline equates 6 mg/dl with 360 µmol/l.

Timing changes the number

During a gout attack, the value can be normal. The S3 guideline writes that values during an attack can be normal or even low, and recommends measuring uric acid again after the inflammation has subsided. Citing a study referenced there, the German general practice guideline from 2023 gives a rate of false normal results of about one third. The NICE guideline recommends repeating the measurement at least two weeks after the attack has settled if gout is strongly suspected and the value during the attack is below 360 µmol/l.

After prolonged fasting, the value can be considerably higher. In a small study of 21 days of water fasting, uric acid more than doubled on average. More on this in the section on the drivers.

Medications shift the value, for example water tablets and low-dose aspirin upwards. More on that shortly.

And your stage of life plays a part. In women, the value shifts with menopause.

How perimenopause shows up overall and when it begins is explained in Perimenopause: recognizing the symptoms and when it begins.

And when uric acid is too low

That happens too. A review around Ben Salem defines hypouricemia as uric acid of 2.0 mg/dl or less. That is the definition used in this review and not a laboratory cut-off for everyone.

As causes, the paper lists severe liver disease, cancer, impaired reabsorption of uric acid in the kidney tubules, inherited disorders of purine metabolism and medications. Drug-induced hypouricemia most commonly occurs when urate-lowering drugs lower the value more than necessary. Some medications outside gout therapy can also lower the value.

One rare but important form is inherited renal hypouricemia. The review around Nakayama describes that it is often accompanied by complications such as exercise-induced acute kidney injury, meaning kidney damage after strenuous physical exertion. How much a merely slightly low value without an identifiable cause matters, on the other hand, has been little studied.

So a very low value is no reason for joy and no reason for panic. It should be assessed by a doctor. If you take urate-lowering medication, the prescribing practice decides on any adjustment.

And now you know why the same number can mean something different depending on the laboratory, the day, your stage of life and your medication list.

Hyperuricemia is not gout: how often the value turns into a disease

This may be the most important sentence in this article: a high uric acid value is a risk factor and not yet gout. Hyperuricemia only means that uric acid in the blood is high. Gout means that crystals have been deposited and trigger inflammation.

There is a long way in between. As a summary figure, the genetics paper around Vitart states that about 10 percent of people with hyperuricemia develop gout. How strongly this depends on the value is shown by a large analysis from the US.

In its full text, the American College of Rheumatology guideline cites a similar order of magnitude from observational data: of people with asymptomatic hyperuricemia above 9 mg/dl, only 20 percent developed gout within five years.

What symptoms does high uric acid cause?

Usually none. That is the honest answer, and for many a reassuring one. Symptoms arise where uric acid precipitates: as a gout attack in a joint, as gout nodules under the skin or as a uric acid stone in the urinary tract.

Online you often read that uric acid makes you tired, causes water retention or a vague aching in the joints. The research for this article found no reliable study on such complaints as a direct consequence of a high value. That does not prove they do not exist. But it does suggest looking for other causes behind fatigue or swelling as well.

Crystals without an attack: what ultrasound shows

And now you know why the sentence "You have uric acid, so you have gout" is not true, and why the sentence "Uric acid is just a lab value" falls just as short.

High uric acid, the causes: kidneys, gut, genes, insulin and medications

You eat sensibly, rarely drink alcohol, and meat is not on the table every day. And still uric acid appears with an asterisk on your report. Research offers a well-studied explanation for this.

The kidney as the bottleneck

A large study around Qi confirms this picture in 4,873 people with gout. Based on how their kidneys handled uric acid, 60.9 percent showed pure underexcretion, 23.1 percent a mixed type, 8.8 percent renal overload and 7.2 percent an unremarkable pattern. This applies to people with gout, not automatically to every case of hyperuricemia.

This fits with what the S3 guideline writes about kidney function: the frequency of gout rises from 16 percent at an estimated filtration rate of 60 ml/min/1.73 m² or more to 35.6 percent at below 30 ml/min/1.73 m². That is why kidney values belong in every assessment of high uric acid.

The second exit: the gut

Genes shift the starting point

Whether your transporters work generously or sparingly is to a large extent inherited. SLC2A9, also called GLUT9, is one example, ABCG2 a second.

Since then, the list has grown long. An analysis around Tin with 457,690 people of different ancestries found 183 gene loci, with the kidneys and liver as the most important target organs. How ancestry and genes shape metabolism overall is covered in Genes, ancestry and metabolism.

Insulin: the bridge to metabolism

This is where it gets interesting from a functional perspective. One of the factors that can narrow the kidney exit is a hormone.

This fits with a cross-sectional study around Facchini: in 36 healthy people without diabetes, insulin resistance was closely related to uric acid and inversely related to the kidneys' uric acid clearance. And in the US health survey NHANES III, 62.8 percent of people with gout had metabolic syndrome, compared with 25.4 percent of those without gout.

For me, this is why high uric acid is first of all an invitation to look at blood sugar, insulin, waist circumference, blood pressure and blood lipids. How insulin resistance develops and why it can make weight loss harder is explained in Insulin resistance and weight loss.

Less often, increased production is behind it, for example with rapid cell breakdown during chemotherapy, a separate situation for the treating oncology team.

Uric acid raised by medications: why stopping them is not the answer

A meta-analysis of cohort studies around Evans found a relative risk of 2.39 for new gout with diuretics. From this, the S3 guideline derives an expert recommendation addressed to physicians (quoted here in translation): "Medications that raise serum uric acid, in particular loop and thiazide diuretics, should only be used with strict indication; possible alternatives should be sought." As further examples, the guideline names metoprolol and low-dose aspirin. It describes the cholesterol-lowering drug bempedoic acid as contraindicated in known gout. This is addressed to prescribers: anyone taking one of these drugs does not stop it on their own, but raises uric acid with the prescribing practice.

There is also the opposite direction. According to the S3 guideline, an SGLT2 inhibitor in diabetes, kidney or heart failure can "additionally have a lowering effect on the uric acid level" (in translation), and losartan and fenofibrate are also described as lowering uric acid, without evidence of fewer gout attacks. The American guideline gives conditional recommendations to prescribers on this, for example to prefer losartan when choosing a blood pressure drug, but advises against switching to fenofibrate specifically because of gout. These are considerations for the prescribing practice and not a call to change anything yourself.

And now you know why high uric acid rarely has a single cause, but usually a sum of kidneys, genes, insulin, medications and only then the plate.

Fructose, alcohol, purines, weight, fasting: what drives the value

Anyone searching for "lowering uric acid" quickly lands on long lists of forbidden foods. Red column, green column, done. It is not that simple. Still, there are drivers that are well studied, each presented here with the question of how certain we are.

Fructose and sugar-sweetened drinks

The large cohort studies come from the US. In 46,393 men, drinking two or more sugar-sweetened soft drinks a day over 12 years was associated with a relative risk of gout of 1.85, compared with less than one serving a month. Diet soft drinks showed no association, whereas fruit juice and fructose-rich fruits did.

Observation is not experiment. That is why controlled feeding trials matter, in which people receive a predefined diet.

To be honest, not everything fits together when it comes to juice. In the cohort of women, orange juice was associated with more gout, whereas in the feeding trials fruit juice lowered the value. I would rather leave this contradiction standing than smooth it over.

Why fructose is processed differently from glucose in the liver is something I explain in Sugar and fructose. Fructose intolerance in the gut is a separate topic, see Lactose, fructose, sorbitol.

Alcohol, especially beer

In people who already have gout, the picture looks different. In a case-crossover study around Neogi with 724 participants, more than one to two alcoholic drinks in 24 hours were associated with a 1.36-fold and more than two to four with a 1.51-fold risk of an attack, and wine, beer and spirits were each associated with more attacks.

The research found no study on alcohol-free beer with uric acid or gout as an outcome, so I cannot say anything reliable about it. What alcohol can do in the gut even in small amounts is covered in Alcohol and the gut.

Purines: meat yes, vegetables hardly

Purines are the classic among uric acid tips, and the data are more nuanced than the lists. In the same cohort of men as above, the highest fifth of meat intake, compared with the lowest fifth, was associated with a relative risk of gout of 1.41, and the highest fifth for seafood with 1.51. Purine-rich vegetables and total protein intake, on the other hand, were not associated with more gout. Dairy products were associated with a lower risk, relative risk 0.56 for the highest versus the lowest fifth.

That is an observation and not a meal plan, but the statement "purine-rich equals bad" is too crude. For protein needs overall, see How much protein do you need. Organ meats are particularly rich in purines, more on this in Organ meats and bone broth.

Weight

In a meta-analysis of cohort studies around Evans, gout was 2.24 times as likely at a BMI of 30 or more, the study definition of obesity. A systematic review around Nielsen found changes in uric acid with weight loss ranging from minus 168 to plus 30 µmol/l in people with gout and overweight, and six of eight studies showed favorable effects on attacks. The evidence was low to moderate, and shortly after bariatric surgery, attacks tended to increase temporarily.

What matters to me here: weight is not a question of character, and a diet is not a harmless tool. A history of dieting and severe restriction carry their own risks, up to disordered eating, see Understanding eating disorders. How many building blocks interact when it comes to weight is shown in Understanding weight holistically.

Fasting and ketosis: why the value rises

This surprises many people: you eat nothing for days, and uric acid goes up.

Even after ten days of fasting, uric acid rose in 109 people in a study around Wilhelmi de Toledo; no gout attacks occurred in this group, which cannot be transferred to people with gout. The usual explanation: ketone bodies can compete with uric acid for excretion in the kidneys. That is mechanistically plausible, but not supported here by a study of its own.

Animal An interesting counter-movement comes from the laboratory. Goldberg and colleagues found in rats with crystal-induced joint inflammation that a ketogenic diet raised the ketone body beta-hydroxybutyrate and dampened the inflammation, and in cell experiments this ketone body inhibited a central inflammatory signal in immune cells from mice and humans. In humans with gout, this has not been clinically tested and is therefore no argument for a ketogenic diet in gout.

A short eating window in everyday life is something different from ten or 21 days without food, and no comparable uric acid data on intermittent fasting are available here. How fasting can influence blood sugar and insulin resistance is covered in Fasting and blood sugar. If you have gout, discuss longer fasting with your doctor beforehand, because it can change uric acid rapidly. The S3 guideline describes attacks mainly with acute changes in uric acid, for example after rapid weight loss, bariatric surgery, excessive alcohol or high purine intake.

And now you know why a list of red and green foods falls short, and where drinks, alcohol and fasting still matter as real levers.

High blood pressure, kidneys, heart: is uric acid culprit or witness?

Perhaps you have read that uric acid is a silent driver of high blood pressure, declining kidney function and heart attacks. And in observational studies, people with high uric acid do indeed have these conditions more often. The only question is whether uric acid causes them or simply happens to be at the scene.

This is not hair-splitting: if uric acid were a cause, lowering it could protect. If it were only a witness, lowering it would likely do little for the heart. Research has approached the question in three ways.

Step one: observation

Step two: genes

So the genetic studies contradict each other. A large genetic analysis around Tin offers a possible explanation: uric acid shares many genetic foundations with other metabolic and cardiac traits, and the analyses pointed to a considerable role of genes with multiple effects. And for the kidneys, another interpretation suggests itself: a kidney that works less well excretes less uric acid. High uric acid would then be more a consequence than a cause. That is a plausible explanation, not proof.

Step three: treatment trials

In the end, what counts is whether lowering it changes anything. Large trials now exist here, and their results for symptom-free hyperuricemia are sobering.

So the large Western trials found no hard benefit for the kidneys or the heart. The Japanese FREED trial and the network meta-analysis of 23 trials are more positive, especially for the kidneys. Important for ALL-HEART: high uric acid was not an inclusion criterion there.

And now you know why the same body of evidence leads to a different recommendation in Japan than in the US, and why neither contradicts your own curiosity about the causes.

Gout attack and gout: symptoms, medical treatment and what the guidelines say

It often starts at night. You wake up, and your big toe is burning. Within a few hours the joint is red, hot and swollen, and even the duvet is too much.

The British NICE guideline describes the typical suspicion in exactly this way: rapid onset, often overnight, severe pain with redness and swelling in one or both big toe base joints. But the midfoot, ankle, knee, hand, wrist or elbow can also be affected. And it explicitly recommends considering septic arthritis, calcium pyrophosphate deposition and inflammatory joint diseases.

That is exactly why a gout attack should be looked at by a doctor. Not every hot joint is gout, and mistaking it for a joint infection can be dangerous. The German general practice guideline points out that general well-being is usually undisturbed during a gout attack, whereas in advanced septic arthritis it is typically worse. The red flags are in the box at the very top.

Gout is also not a series of isolated accidents. The Lancet review around Dalbeth describes it as a chronic disease, even if it shows itself in flares. And an attack is more than a painful toe: in English general practice data, a team around Cipolletta found that heart attacks and strokes occurred more often in the 60 days after a gout attack than in comparison periods of the same people, with an adjusted incidence rate ratio of 1.89. That is an observation, but a good reason to take attacks seriously.

The German S3 guideline: clear on the attack, divided on the target value

Since its revision in 2024, Germany has an interdisciplinary S3 guideline on gout, led by the German Society for Rheumatology and Clinical Immunology, with general practice among the participating disciplines. The most important recommendations, quoted in translation and deliberately without doses. The German wording "soll" (the strongest level) is rendered as "shall", "sollte" as "should" and "kann" as "can":

• Attack, recommendation 3.1, recommendation grade A: "Treatment of an acute gout attack shall be carried out promptly with colchicine, glucocorticoids or non-steroidal anti-inflammatory drugs (NSAIDs) (in alphabetical order) as first-choice agents." The choice shall be guided by concomitant medication, comorbidities and contraindications.
• No improvement, recommendation 3.5: if symptoms do not improve within 24 to 72 hours, "a re-evaluation and, if necessary, an adjustment of therapy should take place".
• Supportive, recommendation 3.6, recommendation grade B: rest, elevation and cooling "should be applied supportively".
• First attack, recommendation 4.1, recommendation grade 0: "At the first gout attack, all therapy options should be discussed with the patient in order to prevent further gout attacks."
• Long-term lowering, recommendation 4.2, recommendation grade 0: therapy with a xanthine oxidase inhibitor should be started in the case of a limiting or impairing attack, more than one gout attack per year or tophaceous gout.
• Target value, recommendation 4.5, recommendation grade 0: "In patients with diagnosed gout on XOI therapy, a serum uric acid of <6 mg/dl should be achieved." In tophaceous gout, "a target serum uric acid of <5 mg/dl can be considered" (4.6, recommendation grade 0).
• Cardiovascular comorbidity, recommendation 5, recommendation grade B: treatment should preferably be with allopurinol, alternatively with febuxostat.

One sentence from the guideline's rationale is particularly important to me, because it contradicts a common impulse: "Urate-lowering therapy that has already been started should not be interrupted because of a renewed gout attack, as fluctuations in the serum uric acid level can in turn favor gout attacks." If you have an attack while on treatment, discuss how to proceed with your treating practice.

And it is honest about the patience required: according to the rationale, significant effects on the number of attacks appear after 12 months at the earliest.

What the international guidelines say

And symptom-free hyperuricemia?

This is where the guidelines diverge most. The American College of Rheumatology guideline states: for people with asymptomatic hyperuricemia, meaning uric acid above 6.8 mg/dl without previous gout attacks or gout nodules, starting drug-based urate lowering with allopurinol, febuxostat or probenecid is conditionally not recommended. The rationale states that in the trials, fewer than 1 percent on treatment and 5 percent on placebo developed gout, and that 24 people would need to be treated for three years to prevent a single first gout attack.

The German S3 guideline applies to people with gout and contains neither a recommendation nor a statement on symptom-free hyperuricemia. The earlier German general practice guideline on chronic gout, now expired and incorporated into the S3, stated (in translation): "The current evidence does not allow a recommendation on the treatment of asymptomatic hyperuricemia." It also advised against routine measurement of uric acid without a specific reason. EULAR and NICE contain no treatment recommendation for symptom-free hyperuricemia in the texts reviewed. According to the review around Hisatome, the Japanese guideline recommends drug treatment in chronic kidney disease.

And now you know why a gout attack belongs in a doctor's practice, why the treatment afterwards requires patience and why a high value without symptoms does not automatically mean a tablet.

Lowering uric acid: what you can influence yourself, sorted by evidence

Now comes the part you may have been looking for first. I will start with an honest expectation.

For the S3 guideline, the German Institute for Quality and Efficiency in Health Care (IQWiG) evaluated randomized trials on lifestyle in gout. Of ten trials, eight compared an active measure with placebo, no treatment or usual care. Six trials reported on the outcome of gout attacks: five of them, with omega-3, tart cherry products, turmeric or skim milk powder, had no significant results or very low quality. Only a small pilot study with a probiotic and 30 participants showed significant effects. Because of its limitations and a high risk of reporting bias, the guideline group did not use it for recommendations. The guideline therefore phrases things cautiously, recommendation 7.1, recommendation grade 0 (in translation): "A healthy, balanced diet with reduced meat consumption, a plant-based emphasis, reduced alcohol consumption and reduction of fructose-enriched foods can be recommended to patients with gout. There is no evidence-based recommendation for a specific diet that reduces gout attacks."

Added to this is recommendation 7.2 with recommendation grade B: education that obesity, overweight and excessive alcohol consumption increase the risk of gout attacks "should take place". The NICE guideline says something similar: there is not enough evidence that any particular diet prevents attacks or lowers uric acid.

So the levers in everyday life are real, but smaller than in many guides, and they do not replace medical gout therapy.

Vitamin C and cherries: two home remedies put to the test

And perhaps that is exactly where the freedom lies with this topic. It is not about fighting a number or never drinking a beer again. It is about improving your chances of quiet nights without a burning toe and understanding your metabolism well enough that the lab report frightens you less.

If you would like not only to read but to interpret your values together: below this article you will find the option to book an appointment.

And now you know why three calm levers can achieve more than a long list of bans.

Frequently asked questions about uric acid

Where uric acid connects to the rest of your metabolism

Uric acid rarely stands alone. It is linked to the liver and fructose, to insulin and weight, to alcohol, to genes and to your stage of life. Here are ten paths that lead on from this article.