What Is Allopurinol? Uses, Dosage, and What You Need to Know in 2026

Allopurinol is one of the most widely prescribed medications in the United States, with millions of Americans taking it daily for gout prevention. Yet many patients start allopurinol without fully understanding how it works, what to expect, or when to be concerned. This comprehensive guide covers everything you need to know about allopurinol in 2026.

What Is Allopurinol?

Allopurinol is a prescription medication that belongs to a class of drugs called xanthine oxidase inhibitors (XOIs). Its primary function is to reduce the amount of uric acid produced in the body. High uric acid levels (hyperuricemia) can cause gout — a painful form of arthritis — and kidney stones. By keeping uric acid levels low, allopurinol prevents these conditions from occurring.

Allopurinol has been on the market since 1966, when it was first approved by the FDA under the brand name Zyloprim. Today it's almost exclusively used as a generic drug, making it one of the most affordable long-term medications available. Other brand names include Lopurin and Aloprim (the IV formulation).

What Conditions Does Allopurinol Treat?

Allopurinol is FDA-approved for three conditions:

1. Gout: Allopurinol is the first-line urate-lowering treatment for chronic gout recommended by the American College of Rheumatology. It prevents gout attacks by keeping uric acid levels at or below 6 mg/dL — the level at which crystals stop forming. Note: allopurinol does NOT treat acute gout attacks; it prevents future ones.
2. Tumor lysis syndrome prevention: In cancer patients receiving chemotherapy, rapidly dying cancer cells release large amounts of uric acid. Allopurinol is started 24–48 hours before chemotherapy to prevent dangerous uric acid buildup (hyperuricemia) and protect the kidneys.
3. Recurrent calcium oxalate kidney stones: For patients who develop calcium oxalate kidney stones due to high uric acid in their urine (hyperuricosuria), allopurinol at 200–300 mg/day can reduce stone formation.

Off-label uses include Lesch-Nyhan syndrome, prevention of uric acid kidney stones, and as an adjunct to azathioprine therapy in inflammatory bowel disease (at reduced azathioprine doses).

What Forms and Strengths Does Allopurinol Come In?

• Oral tablet: 100 mg, 200 mg, 300 mg (most common)
• Intravenous (IV) powder for injection: 500 mg — used in hospital settings for patients who can't take oral medication

How Is Allopurinol Dosed?

For gout, your doctor will start you on a low dose and slowly increase it based on your uric acid levels:

• Starting dose: 100 mg once daily (50 mg in patients with significant kidney disease)
• Titration: Increase by 100 mg every 2–4 weeks until serum uric acid reaches ≤6 mg/dL
• Typical maintenance dose: 200–400 mg/day for most gout patients
• Maximum dose: 800 mg/day (men); 750 mg/day (women)

The target is a serum uric acid level of ≤6 mg/dL. Once you reach this target consistently, gout flares should decrease and eventually stop.

How Should I Take Allopurinol?

• Take at the same time each day — consistency matters
• Take with food or after a meal to reduce nausea
• Take with a full glass of water and drink plenty of fluids throughout the day (8–10 glasses)
• Do NOT stop taking allopurinol if you have a gout flare — continue and treat the flare separately
• It may take several months before you see the full benefit — uric acid doesn't drop overnight

Is Allopurinol a Controlled Substance?

No. Allopurinol is not a controlled substance and has no DEA scheduling. It does not have potential for abuse or dependence. This means it can be prescribed via telehealth in all states, refills are straightforward, and there are no restrictions on the quantity dispensed.

How Much Does Allopurinol Cost?

Allopurinol is one of the most affordable prescription medications available. Without insurance, it typically costs $3–$15 per month with a GoodRx or SingleCare coupon. With insurance, most plans cover generic allopurinol at Tier 1 — often just a $0–$10 copay. For a detailed breakdown, see our guide on how to save money on allopurinol in 2026.

Key Takeaways

• Allopurinol prevents gout by reducing uric acid production — it does not treat acute flares
• It's also approved for tumor lysis syndrome prevention and recurrent calcium oxalate kidney stones
• Start at 100 mg/day and titrate to uric acid target ≤6 mg/dL
• Early flares are expected — don't stop the medication without talking to your doctor
• Stop immediately if you develop any rash and call your doctor