Uric Acid: Causes, Symptoms & Treatment – Complete Guide
- What is uric acid? Normal levels and function
- Causes of high uric acid (hyperuricemia)
- Symptoms of high uric acid – gout, kidney stones, tophi
- Uric acid kidney stones – unique features and treatment
- Diagnosis – blood tests, 24‑hour urine, imaging
- Treatment – medications (allopurinol, febuxostat, probenecid)
- Diet to lower uric acid – what to eat and avoid
- Interactive FAQ – 10 common questions
What is uric acid? Normal levels and function
Uric acid is a waste product formed when the body breaks down purines – substances found naturally in the body and in certain foods (organ meats, seafood, beer). Most uric acid dissolves in the blood, travels to the kidneys, and is excreted in urine. However, if the body produces too much uric acid or the kidneys excrete too little, levels rise – a condition called hyperuricemia.
Normal uric acid levels:
- Men: 3.5‑7.2 mg/dL (210‑430 µmol/L)
- Women: 2.5‑6.0 mg/dL (150‑360 µmol/L)
- For kidney stone prevention, target <6.0 mg/dL for men and <5.5 mg/dL for women.
Hyperuricemia does not always cause symptoms, but when uric acid crystallises, it can cause gout (joints) or uric acid kidney stones.
Causes of high uric acid (hyperuricemia)
Hyperuricemia results from overproduction or underexcretion of uric acid:
- Overproduction (10‑20% of cases): Genetic disorders (Lesch‑Nyhan syndrome), high purine diet (red meat, organ meats, seafood), high fructose intake, obesity, alcohol (especially beer), certain cancers (lymphoma, leukaemia) or chemotherapy (tumour lysis syndrome).
- Underexcretion (80‑90% of cases): Chronic kidney disease, dehydration, medications (thiazide diuretics, low‑dose aspirin, cyclosporine), hypothyroidism, metabolic syndrome, lead toxicity.
- Mixed causes: Idiopathic (unknown) – common.
At Vivekananda Hospital, we perform a 24‑hour urine test to determine whether a patient is an overproducer or underexcreter – this guides treatment (allopurinol for overproducers, uricosuric agents for underexcreters).
Symptoms of high uric acid – gout, kidney stones, tophi
High uric acid itself is asymptomatic. Symptoms arise when urate crystals deposit in tissues:
- Gouty arthritis (gout): Sudden, severe joint pain, swelling, redness, and warmth – most commonly in the big toe (podagra), but also ankles, knees, wrists, and fingers. Attacks often start at night. Gout can become chronic with tophi formation.
- Uric acid kidney stones: Crystals form stones in the kidney, causing flank pain, hematuria, nausea. Unlike calcium stones, uric acid stones are radiolucent (invisible on X‑ray).
- Tophi: Chalky, yellowish deposits of urate crystals under the skin – seen in chronic gout, typically around joints, elbows, ears, or fingers.
- Chronic kidney disease: Long‑standing hyperuricemia can cause urate nephropathy (crystal deposition in kidney tubules), leading to progressive kidney damage.
Uric acid kidney stones – unique features and treatment
Uric acid stones have distinct characteristics that make them different from calcium stones:
- Appearance: Smooth, round, reddish‑brown or brick‑red.
- Radiology: Radiolucent on plain X‑ray (KUB) – they do not show up. Visible on CT (density 200‑500 HU, less than calcium stones).
- Cause: Low urine pH (persistently <5.5) is the most important factor – uric acid is poorly soluble in acidic urine. Dehydration and high purine intake contribute.
- Treatment: Unlike calcium stones, uric acid stones can be dissolved with medical therapy (potassium citrate to raise urine pH to 6.5‑7.0). Dissolution takes 3‑6 months. For large stones causing obstruction, ureteroscopy with laser is effective.
- Prevention: Alkalinise urine (potassium citrate), allopurinol (reduce uric acid production), high fluid intake, low purine diet.
Diagnosis – blood tests, 24‑hour urine, imaging
Diagnosing hyperuricemia and uric acid stones involves several steps:
- Blood test (serum uric acid): Measures uric acid level. For stone formers, target <6.0 mg/dL (men) or <5.5 mg/dL (women).
- 24‑hour urine test: Measures urine volume, pH, uric acid excretion, calcium, oxalate, citrate. Low urine pH (<5.5) suggests uric acid stone risk. Uric acid excretion >800 mg/day in men or >750 mg/day in women indicates overproduction.
- Stone analysis: Infrared spectroscopy of passed or removed stones – definitive diagnosis.
- Imaging: Non‑contrast CT shows uric acid stones (less dense than calcium stones). Ultrasound may miss small stones but detects hydronephrosis.
Treatment – medications (allopurinol, febuxostat, probenecid)
Treatment of hyperuricemia depends on the underlying cause:
- Allopurinol (Zyloric): First‑line for overproducers and most gout patients. Dose 100‑300 mg daily. Reduces uric acid production. Side effects: rash (rare, but serious), nausea. HLA‑B*5801 testing recommended before use in high‑risk populations (Asian descent).
- Febuxostat (Febucare, Adenuric): Alternative for patients intolerant to allopurinol. Dose 40‑80 mg daily. More expensive. Black box warning for cardiovascular events in patients with existing heart disease.
- Probenecid: Uricosuric agent for underexcreters – increases uric acid excretion. Dose 500‑1000 mg twice daily. Requires adequate hydration to prevent stone formation.
- Potassium citrate (Urocit K, Cytra K): For uric acid stones – alkalinises urine to pH 6.5‑7.0. Dose 20‑60 mEq daily. Can dissolve existing stones.
- Acute gout treatment: NSAIDs (ibuprofen, naproxen, diclofenac), colchicine, or corticosteroids. Do not start allopurinol during an acute flare – it can worsen symptoms.
Diet to lower uric acid – what to eat and avoid
Dietary changes can lower uric acid by 1‑2 mg/dL – significant but often not enough alone for severe hyperuricemia. Combine with medication.
Foods to avoid (high purine):
- Organ meats: liver, kidney, brain, sweetbreads
- Game meats: venison, rabbit, goose
- Certain seafood: sardines, anchovies, mackerel, herring, scallops, mussels, tuna
- Red meat: beef, pork, lamb – limit to 1‑2 servings/week
- Beer and hard liquor – beer is especially high in purines
- Sugary drinks and foods with high fructose corn syrup
Foods to eat (low purine):
- Low‑fat dairy (milk, yoghurt, cheese) – may actually lower uric acid
- Vegetables (all, including peas, beans, lentils – contrary to old myths, vegetables do not increase uric acid)
- Fruits (except avoid excessive fructose – limit fruit juice)
- Whole grains, nuts, eggs
- Coffee (moderate amounts may lower uric acid)
- Water – 2.5‑3 litres daily
Cherries and cherry juice have modest uric acid‑lowering effects – 1‑2 cups daily may help.
Interactive FAQ – Uric acid
Levels >10 mg/dL significantly increase risk of gout and kidney stones. For stone formers, target <6 mg/dL (men) or <5.5 mg/dL (women).
Yes – chronic hyperuricemia can cause urate nephropathy, where crystals deposit in kidney tubules, leading to chronic kidney disease. Treating hyperuricemia may slow progression.
Dietary changes can lower uric acid by 1‑2 mg/dL within 4‑6 weeks. For most patients with gout or stones, medication is needed to reach target levels.
Yes – hydration increases urine volume, diluting uric acid and reducing stone risk. However, it does not significantly lower serum uric acid – that requires medication or diet.
Yes, allopurinol is safe for long‑term use in most patients. Rare side effects include severe rash (DRESS syndrome) – stop immediately if rash appears. HLA‑B*5801 screening reduces risk.
Vitamin C (500 mg daily) may slightly lower uric acid by increasing renal excretion. However, high doses (>1000 mg) can increase oxalate and cause calcium oxalate stones – not recommended.
Moderate coffee consumption (2‑3 cups daily) is associated with lower uric acid levels and reduced gout risk. The effect is from caffeine and antioxidants, not diuresis.
Sometimes, but not reliably. Uric acid stones are radiolucent on X‑ray and may be missed on ultrasound if small. Non‑contrast CT is the gold standard.
Both reduce uric acid production. Febuxostat is more expensive and has a black box warning for cardiovascular events. Allopurinol is first‑line due to cost and safety profile.
No – hyperuricemia is usually a chronic condition. Stopping medication will cause uric acid to rise again. Continue lifelong therapy unless the underlying cause is corrected (e.g., stopping a medication).
Disclaimer: This information is for educational purposes. If you have high uric acid, gout, or uric acid kidney stones, consult a urologist or rheumatologist at Vivekananda Hospital for personalised treatment.