What is Uric Acid and Why Does it Build Up? 

Uric acid is a natural waste product found in the blood, created when the body breaks down chemicals called purines. While it is usually a harmless substance that the body filters out effectively, problems arise when the balance between production and excretion is disrupted. When uric acid levels become too high, a state known as hyperuricaemia, it can lead to the formation of painful crystals in the joints. Understanding exactly what this substance is and why your body might be holding onto too much of it is the first step in managing conditions like gout and protecting your long-term kidney health. 

What We’ll Discuss in This Article 

• The biological definition of uric acid and its origin in purines 

• How the body typically processes and eliminates this waste product 

• The difference between overproduction and under-excretion 

• Key factors that cause levels to rise, including diet and genetics 

• The relationship between uric acid buildup and joint inflammation 

• When high uric acid levels require urgent medical investigation 

Defining Uric Acid and Purines 

Uric acid is a byproduct of the metabolic breakdown of purines. Purines are nitrogen-containing compounds that are essential for life; they are found in the DNA and RNA of every cell in your body. When cells grow, die, and are replaced, these purines are broken down, and uric acid is produced as the final waste result. It is also found in many of the foods we eat, meaning our total uric acid level is a combination of what our body produces internally and what we ingest through our diet. 

In a healthy system, uric acid dissolves in the blood and travels to the kidneys. From there, it is filtered out and leaves the body through urine, with a smaller amount excreted through the digestive tract. According to NHS information on high uric acid, problems only occur when the concentration in the blood exceeds the point where it can stay dissolved, leading to the precipitation of solid crystals. 

Internal source: 

The natural breakdown of the body’s own cells. 

External source: 

The digestion of purine-rich foods and drinks. 

Solubility: 

The ability of blood to hold uric acid in a liquid state. 

Crystallisation: 

The process of the acid turning into solid, needle-like urate. 

Why Uric Acid Builds Up: Overproduction 

One reason uric acid builds up is that the body produces more than it can handle. This overproduction can be caused by a variety of factors. Certain medical conditions that cause rapid cell turnover—such as psoriasis or some blood disorders—can lead to a spike in uric acid because the body is breaking down more DNA than usual. 

Dietary choices are the most common driver of overproduction. Consuming large quantities of high-purine foods, such as red meat, game, and specific seafood (like sardines or shellfish), provides the body with an excess of raw material to turn into uric acid. Furthermore, fructose—a sugar found in many processed drinks and sweets—uniquely stimulates the liver to produce uric acid as it is metabolised. High alcohol intake also forces the liver to produce more urate while simultaneously hindering the body’s ability to get rid of it. 

Cell Turnover: 

Rapid growth or death of body cells releasing purines. 

High-Purine Diet: 

Over-consumption of meats and seafood. 

Fructose Impact: 

Sugary drinks stimulating chemical production in the liver. 

Alcohol Breakdown: 

The metabolic byproduct of drinking, especially beer. 

Why Uric Acid Builds Up: Under-Excretion 

For the vast majority of people with high levels (about 90% of cases), the buildup isn’t caused by eating too much purine, but by the kidneys not getting rid of enough uric acid. This is known as “under-excretion.” Even if you eat a perfectly balanced diet, if your kidneys are not filtering efficiently, uric acid will gradually accumulate in the bloodstream. 

This lack of clearance is often linked to kidney health. As we age, or if we develop conditions like high blood pressure or diabetes, the kidneys’ filtration units can become less effective. Genetics also play a major role here; some people are simply born with kidneys that are genetically “programmed” to reabsorb more uric acid back into the blood rather than letting it pass into the urine. This explains why gout often runs in families, regardless of shared dietary habits. 

The Impact of Medications and Dehydration 

External factors can also temporarily or permanently reduce the body’s ability to clear uric acid. Dehydration is a common cause of sudden buildup; when there is less fluid in the blood, the concentration of uric acid naturally rises, and there is less water available for the kidneys to flush waste away. This is why many gout attacks occur after periods of heavy sweating or inadequate water intake. 

Certain medications can also interfere with the kidneys’ handling of urate. Diuretics, or “water tablets,” which are frequently used to treat high blood pressure, can cause the kidneys to hold onto uric acid. Low-dose aspirin and some medications used after organ transplants can have a similar effect. If you are starting a new medication and notice joint sensitivity, it is vital to monitor your symptoms closely. 

From Buildup to Inflammation 

It is important to note that having a buildup of uric acid (hyperuricaemia) does not always cause symptoms. Many people live with high levels for years without experiencing pain. However, for some, the high concentration eventually leads to the formation of monosodium urate crystals. These crystals tend to settle in areas where the temperature is slightly lower, such as the joints of the feet and hands. 

Once these crystals are lodged in the joint, they act like tiny needles. The body’s immune system detects them as foreign objects and sends white blood cells to attack them. This “battle” between the immune system and the crystals is what causes the intense inflammation, heat, and pain of a gout flare. Without addressing the underlying buildup of uric acid, these crystals will continue to deposit, potentially leading to long-term joint damage or kidney stones. 

Conclusion 

Uric acid is a natural waste product that becomes problematic only when it builds up to excessive levels in the blood. This buildup is usually a result of the kidneys not excreting it efficiently, though diet and high cell turnover can also contribute to overproduction. Maintaining a healthy weight, staying hydrated, and understanding your genetic risks are key to keeping uric acid in check and preventing the painful crystallisation that leads to gout. 

If you experience severe, sudden, or worsening symptoms, especially if accompanied by a high temperature or feeling generally unwell, call 999 immediately or visit an A&E department, as these can be signs of a serious joint infection (septic arthritis). 

Authority Snapshot (E-E-A-T Block) 

This article was written by Dr. Stefan Petrov, a UK-trained physician with an MBBS and extensive experience across general medicine, emergency care, and anaesthesia. Dr. Petrov is certified in BLS and ACLS and has worked within hospital wards and intensive care units to provide patient-focused clinical guidance. This guide provides a comprehensive overview of gout based on NHS and NICE standards to ensure you receive accurate, safe, and evidence-based medical information.