Allopurinol — what it is and why people take it

Allopurinol lowers uric acid in the blood. That’s its main job. Doctors prescribe it mainly to prevent gout attacks, reduce uric acid after chemotherapy (tumor lysis syndrome), and help stop uric-acid kidney stones. It won’t stop a sudden gout flare — it’s for prevention, not fast pain relief.

How it works and when to use it

Allopurinol blocks an enzyme called xanthine oxidase, which the body uses to make uric acid. Over time that lowers uric acid levels and reduces crystal buildup in joints and tissues. People usually start it when they have frequent gout attacks, visible tophi (crystal lumps), very high uric acid, or repeated kidney stones tied to uric acid. Your doctor may also use it before certain cancer treatments to prevent a sudden uric acid surge.

Expect results over weeks to months. Uric acid often needs testing and dose changes until you reach the target level your clinician wants — commonly under 6 mg/dL, though your target may differ.

Dosing, side effects and safety tips

Typical practice is to start low and go slow. Many people begin at 50–100 mg daily, especially if kidney function is reduced, and then increase until uric acid is controlled. Some patients stay on 100–300 mg/day; others need higher doses. Always follow the dose your prescriber sets and check kidney or liver tests as recommended.

Common side effects are mild: stomach upset, rash, or headache. A new skin rash matters — stop the drug and contact your prescriber if you get one. A rare but serious reaction is allopurinol hypersensitivity syndrome (fever, worsening rash, kidney problems, liver issues). Risk is higher with poor kidney function and in people with certain genetic markers (for example HLA-B*5801 in some Asian groups). If you belong to a higher-risk group, your doctor may test before starting.

Watch for drug interactions. Allopurinol can make azathioprine or mercaptopurine much more toxic, so those combinations need careful dose changes or usually are avoided. It can also affect some blood thinners and other medicines — always tell every clinician and your pharmacist that you take allopurinol.

Starting allopurinol can trigger short-term gout flares as uric acid levels shift. That’s normal. Doctors often prescribe low-dose colchicine or an NSAID for the first few months to reduce flare risk.

Practical checklist before you start: get baseline blood tests (kidney, liver, uric acid), review other meds for interactions, ask about genetic risk if you’re from a high-risk ethnic group, and plan follow-up testing. If you’re pregnant, breastfeeding, or have active liver or severe kidney disease, talk to your doctor — the plan may change.

Want to learn more? Check reliable sources, ask your pharmacist, and keep a list of symptoms to report. With the right monitoring, allopurinol is a useful option to lower uric acid and prevent future problems.