If you accidentally took 2 allopurinol (Zyloprim), call Poison Control at 1-800-222-1222 or your pharmacist now. Tell them your usual daily dose and whether you have kidney disease. Those two facts help them judge how much the extra tablet matters. Call 911 for trouble breathing or swelling of your lips, mouth or throat.
The US call is free and confidential, according to Poison Control. In Canada, call 1-844-764-7669, or 1-800-463-5060 in Quebec (Health Canada).
The NHS says: "Taking an extra dose of allopurinol is unlikely to cause problems, but it's important to get medical advice if you take too much as it can sometimes be dangerous." Two facts from the FDA label help explain that "sometimes": normal doses differ a lot from person to person, and the drug leaves your body through the kidneys.
This article provides general information about medication management and is not a substitute for professional medical advice. Consult your doctor or pharmacist for advice specific to your medications.
What to Do If You Accidentally Took 2 Allopurinol
- Check the bottle. Allopurinol tablets come in 100, 200 and 300 mg. So "two pills" can mean 200, 400 or 600 mg.
- Add up today. Count every tablet you took today, and say if your plan is twice a day.
- Call with the facts. Give your daily dose, any kidney disease and your other medicines. The label flags several, including warfarin, azathioprine, mercaptopurine and thiazide water pills.
- Ask about your next dose before it's due. Don't decide on your own whether to take it.
- Watch for a rash. The label says to stop allopurinol and get medical help right away at the first sign of one.
Not sure the second pill was allopurinol? See what to do if you took the wrong pill, and call anyway. For other medicines, see taking medication twice by mistake.
Can You Take 2 Allopurinol at Once?
The label limits how much goes in at one time: "Doses in excess of 300 mg should be administered in divided doses." Two 300 mg tablets swallowed together are 600 mg at once. That's twice the largest single dose the label describes, even for people who take 600 mg over a whole day.
Two 100 mg tablets make 200 mg, which is under that 300 mg line. If your plan is 200 mg a day, taking both at once may be exactly what your prescription says. If your plan is 100 mg, the second one is still an extra dose.
When a dose is missed, the label says there's no need to double up: "If a single dose of allopurinol tablets is occasionally forgotten, there is no need to double the dose at the next scheduled time."
Is 600 mg of Allopurinol Too Much?
For some people, 600 mg is a normal day. For people whose kidneys work normally, the FDA label starts at 100 mg a day. The dose goes up 100 mg a week until uric acid hits the target, to at most 800 mg a day. Mild gout is usually controlled with 200 to 300 mg a day, it says, and moderate to severe gout with tophi (uric acid lumps) at 400 to 600 mg.
| What you took | Total | Where it sits on the FDA label | What to do |
|---|---|---|---|
| Two 100 mg tablets | 200 mg | Inside the 100 to 200 mg "minimal effective dosage." Four times the 50 mg start for weaker kidneys | Call Poison Control or your pharmacist |
| Two 200 mg tablets | 400 mg | Low end of the 400 to 600 mg a day for moderate to severe gout with tophi. Above the 300 mg given at one time | Call Poison Control or your pharmacist |
| Two 300 mg tablets | 600 mg | Top of that 400 to 600 mg range. Twice the 300 mg given at one time | Call Poison Control or your pharmacist |
| An extra 300 mg on a 300 mg twice-a-day plan | 900 mg that day | Above the 800 mg daily maximum | Call Poison Control or your pharmacist |
Every row ends the same way on purpose. The table tells you where your number sits on the label. It can't tell you what that number means for you.
Allopurinol Max Dose With Kidney Disease
Your body turns allopurinol into oxipurinol, the form that does most of the work. Your kidneys clear both. The label says changes in kidney function have "a profound effect" on how much of the drug your body is exposed to.
So the label starts people with weaker kidneys much lower. With an eGFR (a kidney score from a blood test) above 30 and up to 60, the starting dose is 50 mg a day. Above 15 and up to 30, it's 50 mg every other day. The label also says a maximum dose for each level of kidney function "is not defined."
If you have kidney disease, say so first when you call.
What Happens If You Take Too Much Allopurinol?
The FDA label's overdose section says there is "no specific antidote for allopurinol tablets." Dialysis can remove both allopurinol and oxipurinol. But the label says how useful that is in an overdose is "unknown."
Two published cases point back to the kidneys. Doctors in Australia reported an acute allopurinol overdose in a patient with advanced chronic kidney disease and measured the drug in the blood. A 2018 case report that shows up for "allopurinol overdose" is about a 12-year-old with a rare genetic condition called Lesch-Nyhan syndrome. He had taken allopurinol since age 2. By the time of the report, his dose was about double the recommended amount for his weight, and he had kidney stones. That's a long-term dosing problem in a rare disease, not one extra pill.
A 2025 simulation study found that missing one or two doses, even repeatedly over a year, did not significantly change whether people reached their uric acid goal. That study was about missed doses. Let your pharmacist or Poison Control decide what comes next.
Allopurinol Overdose Symptoms and Warning Signs
The label lists nausea, diarrhea and raised liver tests as the most common side effects, and calls skin rash the most frequent reaction overall. Drowsiness and dizziness have been reported too. If they hit, the NHS says to wait until they pass before you drive.
The label says to stop allopurinol and get medical help right away for a skin rash, blisters, fever, painful urination, blood in the urine, eye irritation, or swelling of the lips or mouth. Call 911 for trouble breathing or a swollen throat or tongue, which the NHS lists as signs of a severe allergic reaction.
For yellow skin or eyes, itching or extreme tiredness, MedlinePlus says to stop allopurinol and call your doctor right away or get emergency treatment. The label also asks you to report unusual bleeding or bruising, loss of appetite or signs of infection to your doctor.
The label says starting low and going up slowly lowers the risk of serious reactions. It adds that severe skin reactions mostly happen in the first few months. A 2012 study also tied higher starting doses, measured against kidney function, to a higher risk of allopurinol hypersensitivity syndrome. That's a rare but potentially fatal reaction. If you're new to allopurinol or have weaker kidneys, make sure your prescriber hears about the extra tablet.
Was It the Allopurinol or the Colchicine?
The allopurinol label recommends colchicine or another anti-inflammatory to prevent flares when you start, so you may have two gout bottles at home.
Not sure which one you doubled? The colchicine label says if you take too much, "go to the nearest hospital emergency room right away." You can call Poison Control on the way. The label warns that deaths have followed as little as 7 mg taken over four days, and that toxicity usually starts within 24 hours with stomach pain, nausea, vomiting and diarrhea. So diarrhea after a mix-up may not be the allopurinol. Our colchicine guide covers colchicine doses.
Can You Take Extra Allopurinol During a Gout Attack?
It can be tempting to take an extra allopurinol when a flare hits. The label says starting low and raising the dose slowly "decreases the risk of gout flares." It also says shifting uric acid levels can set off flares. During a flare, allopurinol "need not be discontinued," and the flare is treated alongside it, as your prescriber decides.
If flares keep pushing you toward extra tablets, ask your prescriber for a written flare plan. Our guide to gout flares after starting allopurinol explains the bumpy first months. If a flare followed a night out, see allopurinol and alcohol. And if you've been leaning on cherry juice, here's why allopurinol does the real work.
How Pillo Helps
If the extra tablet came from a memory gap, the fix is a record you can check. Pillo's persistent alarm keeps going until you respond. Once you mark the dose as taken, Adherence Reporting keeps it in your dose history. A pill box can't do that, which is why a pill organizer alone won't stop dose mistakes.
Take colchicine too? Pillo's Pill Identifier lets you type the imprint code or scan a tablet to see what it is. Dose Notes let you note what each tablet looks like next to the right medicine. It's a lookup, not a clinical check. Pillo is free for unlimited medications, with ads, and you can manage a parent's gout medicines too, free for up to two dependents.
Frequently Asked Questions
What if I accidentally took 600 mg of allopurinol?
Call Poison Control at 1-800-222-1222 (1-844-764-7669 in Canada) or your pharmacist. The FDA label lists 400 to 600 mg a day for moderate to severe gout with tophi. But it also says doses above 300 mg should be split, and people with weaker kidneys start at 50 mg a day or less. Tell them your usual dose and any kidney disease.
Should I skip my next dose after accidentally taking 2 doses of allopurinol?
Don't decide on your own. Tell Poison Control or your pharmacist when your next dose is due, and they will tell you what to do with it.
I can't remember if I took my allopurinol. Should I take another?
The NHS says not to take 2 doses to make up for a missed one. If you truly can't tell, call your pharmacist before taking another tablet. Here's more on what to do when you can't remember taking your medication.
Can you take allopurinol twice a day?
Yes, if that's how it's prescribed. The label allows split doses and says doses above 300 mg should be split. Twice a day means two planned doses. A third tablet that day is still a call to your pharmacist.
How long does allopurinol stay in your system?
Allopurinol itself has a half-life of about 1 to 2 hours. Its active form, oxipurinol, has a half-life of about 15 hours, according to the FDA label. Both are cleared by the kidneys.
This article is for informational purposes only and does not constitute medical advice. If you think you or someone else took too much allopurinol, call Poison Control at 1-800-222-1222 (1-844-764-7669 in Canada), or 911 in an emergency.
Sources
- Allopurinol tablets prescribing information (NorthStar Rx), DailyMed
- Allopurinol tablets 100 mg, 200 mg and 300 mg prescribing information, DailyMed
- Colcrys (colchicine) prescribing information, DailyMed
- Allopurinol: a medicine to treat gout, NHS
- Allopurinol, MedlinePlus
- Poisoning, MedlinePlus
- Double dosing: What to do if you take too much, Poison Control
- Canada launches new toll-free 1-844 POISON-X number for poison centres, Health Canada
- White-Koning M, et al. Relative forgiveness of different allopurinol implementation patterns in people with gout. Clin Pharmacokinet. 2025
- Stamp LK, et al. Starting dose is a risk factor for allopurinol hypersensitivity syndrome. Arthritis Rheum. 2012
- Kannangara DR, et al. Oxypurinol, allopurinol and allopurinol-1-riboside in plasma following an acute overdose of allopurinol in a patient with advanced chronic kidney disease. Br J Clin Pharmacol. 2012
- Shields LBE, et al. Xanthine calculi in a patient with Lesch-Nyhan syndrome and factor V Leiden treated with allopurinol: case report. BMC Pediatr. 2018
