Uric acid is the acid that causes gout. When uric acid builds up in your bloodstream beyond a critical concentration, it forms sharp, needle-like crystals inside joints, triggering the intense pain and swelling of a gout attack. Normal blood levels sit below 6.8 mg/dL, which is the approximate solubility limit. Above that threshold, uric acid can crystallize in tissue.
How Your Body Produces Uric Acid
Uric acid is the end product of purine metabolism. Purines are compounds found in every cell of your body and in many foods. When cells break down or you digest purine-rich food, the purines are converted first into a molecule called hypoxanthine, then into xanthine, and finally into uric acid. A single enzyme, xanthine oxidase, drives both of those last two conversion steps. This enzyme is also the target of the most common gout medications, which work by slowing uric acid production at the source.
Your body also has a recycling system, called the salvage pathway, that reclaims some purines before they ever reach the uric acid stage. When this recycling works well, less uric acid is generated. When it doesn’t, or when purine intake overwhelms the system, uric acid levels climb.
Why Uric Acid Forms Crystals in Joints
Having elevated uric acid in your blood doesn’t automatically mean you’ll get gout. Crystals form when local conditions push uric acid past its solubility point. Temperature plays a surprisingly large role: a drop of just 2°C (about 3.6°F), from normal body temperature of 37°C down to 35°C, lowers the solubility threshold from 6.8 mg/dL to 6.0 mg/dL. This is one reason gout so often strikes the big toe, the coolest joint in the body, farthest from the core.
Acidity matters too. A lower pH in joint fluid promotes crystal formation through two routes: it directly encourages crystals to nucleate, and it raises local calcium levels, which further reduces uric acid’s ability to stay dissolved. Once the needle-shaped crystals of monosodium urate deposit in a joint, the immune system treats them as foreign invaders, launching an inflammatory response that causes the redness, heat, and extreme tenderness of a gout flare.
Why Uric Acid Builds Up
About 90% of the uric acid filtered by your kidneys is reabsorbed back into the bloodstream rather than excreted. This means your kidneys are already walking a fine line, and anything that tips the balance toward less excretion or more production can push levels into the danger zone. Most cases of gout are driven by the kidneys not clearing enough uric acid, rather than the body making too much of it.
In the kidney’s proximal tubule, specialized transporter proteins shuttle uric acid back and forth between your blood and urine. Two transporters on the cell surface, known as URAT1 and GLUT9, work together to pull uric acid out of urine and return it to the bloodstream. On the excretion side, a different transporter called ABCG2 pumps uric acid out. When any of these transporters malfunction, uric acid accumulates.
Genetics and Uric Acid Levels
The gene most strongly linked to gout risk is SLC2A9, which encodes the GLUT9 transporter. Certain variants of this gene actually lower uric acid levels and reduce gout risk by shifting the balance of uric acid reabsorption in the kidney. Other variants do the opposite.
The ABCG2 gene carries some of the most dramatic risk. A common variant called Q141K cuts uric acid excretion by roughly 54%. A rarer variant, Q126X, nearly eliminates the transporter’s function altogether. People who carry both variants can lose more than 75% of this transporter’s capacity, substantially raising their gout risk. ABCG2 also exports uric acid through the intestines, so when it’s impaired, you lose a second exit route for clearing uric acid from the body.
Foods That Raise Uric Acid
Because uric acid comes from purine breakdown, foods high in purines directly increase your blood levels. The worst offenders are organ meats like liver, kidney, and sweetbreads. Red meats (beef, lamb, pork) are moderate sources. Among seafood, anchovies, sardines, shellfish, and codfish are particularly high in purines.
One finding that surprises many people: vegetables high in purines, such as asparagus, spinach, and green peas, do not raise gout risk. The reason isn’t entirely clear, but studies consistently show that plant-based purines behave differently in the body than animal-based ones.
Fructose Is a Hidden Driver
Sugar-sweetened drinks and foods high in fructose raise uric acid through a completely different mechanism than purine-rich foods. When your liver processes fructose, it rapidly burns through a molecule called ATP, your cells’ energy currency. That rapid depletion generates a surge of a breakdown product called AMP, which feeds directly into the purine degradation pathway and gets converted into uric acid. In other words, fructose doesn’t contain purines, but it forces your body to create them. This makes sodas, fruit juices with added sugar, and high-fructose corn syrup significant gout triggers that many people overlook.
How Different Alcoholic Drinks Compare
Beer carries the highest gout risk of any alcoholic beverage. It hits you from two directions: the ethanol itself inhibits uric acid excretion by the kidneys, and beer is rich in compounds that are metabolized into uric acid, increasing production at the same time. It’s a double problem that other drinks don’t share to the same degree.
Spirits have fewer purines than beer, but their high ethanol concentration promotes lactic acid production, which competes with uric acid for excretion through the kidney. The result is that uric acid backs up in your blood, even without extra purine intake.
Wine appears to carry the lowest risk among alcoholic drinks. Red wine contains polyphenolic compounds that may counteract some of the ethanol’s harmful effects by reducing oxidative stress and inhibiting xanthine oxidase, the same enzyme that gout medications target. This protective effect is dose-dependent, though. Beyond moderate intake, the damage from ethanol overtakes any benefit from polyphenols.
What the Numbers Mean
Hyperuricemia, the medical term for elevated uric acid, is typically defined as levels above 7.0 mg/dL in men and above 6.0 mg/dL in women. Not everyone with hyperuricemia develops gout, but the higher your levels and the longer they stay elevated, the greater the chance that crystals will form in your joints.
For people already diagnosed with gout, the American College of Rheumatology recommends a treatment target of below 6 mg/dL, which sits comfortably under the 6.8 mg/dL solubility threshold. Staying below this level allows existing crystal deposits to slowly dissolve over months to years, reducing the frequency and severity of flares. Treatment typically involves medications that either block xanthine oxidase to reduce uric acid production or enhance kidney excretion, with doses adjusted based on repeated blood tests until the target is reached.