Methotrexate is one of the most commonly prescribed drugs for rheumatoid arthritis, psoriasis, and other inflammatory conditions, and it comes with a meaningful list of things to steer clear of. Some interactions raise the risk of serious side effects, while others can quietly undermine how well the drug works. Here’s what you need to know.
NSAIDs Like Ibuprofen and Naproxen
This is one of the most common and underappreciated risks. Over-the-counter painkillers like ibuprofen (Advil, Motrin) and naproxen (Aleve) can interfere with how your kidneys clear methotrexate from your body, allowing it to build up to toxic levels. A study of patients on low-dose methotrexate found that taking NSAIDs at the same time raised the risk of serious adverse events by 40%, with kidney failure and dangerously low blood cell counts among the specific complications.
This doesn’t mean you can never take an anti-inflammatory again. Many rheumatologists do prescribe NSAIDs alongside methotrexate, but with careful monitoring. The key is to avoid casual, frequent self-dosing with these drugs. Acetaminophen (Tylenol) is generally considered a safer choice for routine pain relief, though it has its own limits for people with liver concerns. Talk to your prescriber before reaching for any painkiller regularly.
Alcohol
Methotrexate is processed through the liver, and alcohol adds stress to an organ that’s already working harder than usual. Over time, the combination increases the risk of liver fibrosis and cirrhosis. In studies of rheumatoid arthritis patients on methotrexate, about 7% developed mild liver fibrosis after cumulative doses of 1.5 grams or more, and a history of heavy drinking is one of the strongest risk factors.
Current guidelines don’t require total abstinence for most people. National recommendations suggest keeping alcohol well within standard limits: no more than two to three units a day for women and three to four for men, with at least one or two alcohol-free days each week. If you have psoriasis or psoriatic arthritis, the threshold is stricter: no more than six units per week, because these conditions carry an independently higher risk of liver damage. A unit is roughly half a pint of beer or a small glass of wine.
Herbal Supplements and Certain Teas
Several popular supplements can cause real problems with methotrexate. The ones with the strongest evidence of interaction include:
- Echinacea: Often taken for immune support, it can work against methotrexate’s intended effect of calming an overactive immune system. Combining the two may reduce the drug’s effectiveness.
- St. John’s wort: Classified as having high interaction potential with multiple medications, including methotrexate. It can alter how your body processes the drug.
- Green tea extract: High-dose green tea supplements or large amounts of brewed green tea should be avoided. Green tea extracts have been specifically flagged as unsafe to combine with methotrexate.
- Willow bark: Contains natural salicylates, compounds chemically similar to aspirin. These can reduce the kidney’s ability to clear methotrexate, potentially raising drug levels in your blood by a meaningful amount.
A good rule of thumb: tell your prescriber about every supplement you take, even ones that seem harmless. “Natural” does not mean free of drug interactions.
Live Vaccines
Because methotrexate suppresses parts of the immune system, live vaccines pose a risk. Live vaccines contain weakened but active viruses, and a suppressed immune system may not be able to handle them safely. The CDC lists known severe immunosuppression as a contraindication for the MMR (measles, mumps, rubella) and varicella (chickenpox) vaccines. The shingles vaccine is listed as a precaution for people on low-dose methotrexate.
Inactivated vaccines, like the flu shot or COVID boosters, are generally considered safe and are actually encouraged since methotrexate can make you more vulnerable to infections. If you need a live vaccine, your doctor may recommend pausing methotrexate temporarily, though specific timing varies by situation.
Sun Exposure and UV Light
Methotrexate can make your skin significantly more sensitive to ultraviolet light. When UV rays interact with the drug in your system, the result can be a phototoxic reaction: skin damage that looks and feels like a severe sunburn or rash, even from sun exposure that wouldn’t normally bother you. Photoallergic reactions, where the immune system overreacts to UV-altered skin, are also possible.
The UK’s medicines regulator specifically advises patients on methotrexate to avoid intense sunlight between 11 a.m. and 3 p.m., skip tanning beds entirely, use high-SPF sunscreen, and wear a hat and clothing that covers the arms and legs when outdoors. This applies year-round, not just in summer.
Pregnancy and Conception
Methotrexate can cause serious birth defects and pregnancy loss. This applies to both women taking the drug and men whose partners could become pregnant. If you’re planning a family, the drug label recommends women wait three to six months after stopping methotrexate before trying to conceive, though some providers consider one to three months sufficient. Reassuringly, studies have not found methotrexate-related birth defects in babies born to women who stopped the drug before conception.
For men, the recommendation is to use effective contraception while on methotrexate and for at least three months after the final dose. This waiting period allows the body to fully clear the medication and produce unaffected sperm.
Skipping Your Folic Acid
This isn’t something to avoid taking, but rather something to avoid forgetting. Folic acid supplementation is a standard part of methotrexate therapy because the drug works partly by interfering with folate metabolism, which is also what causes many of its side effects: mouth sores, nausea, fatigue, and abnormal blood counts. A common dosing approach is 5 mg of folic acid taken the morning after your methotrexate dose. Skipping it consistently can make side effects noticeably worse.
Caffeine: Less Clear Than You Might Think
You may have heard that coffee reduces methotrexate’s effectiveness. The evidence is mixed. Animal studies and some research in rheumatoid arthritis patients have suggested caffeine can blunt the drug’s benefits, since methotrexate works partly through a pathway that caffeine directly opposes. However, a study of 64 patients with psoriasis and psoriatic arthritis found no correlation between caffeine intake and the methotrexate dose needed to control their disease. The effect may depend on which condition you’re treating. If you drink several cups of coffee a day and feel your methotrexate isn’t working well, it’s worth mentioning to your doctor, but blanket caffeine avoidance isn’t currently a standard recommendation.
Kidney and Liver Concerns
Methotrexate is cleared primarily through the kidneys, so anything that impairs kidney function can cause the drug to accumulate dangerously. Dehydration is a common and avoidable risk factor. Staying well hydrated, especially during illness, hot weather, or exercise, helps your kidneys process the drug efficiently. If you develop vomiting, diarrhea, or any illness that limits fluid intake, contact your prescriber, as even temporary dehydration can shift methotrexate levels.
For the liver, the combination of methotrexate with other liver-stressing substances (alcohol, certain supplements, acetaminophen in high doses) is what drives the greatest risk over time. Your provider will monitor liver function through regular blood tests, typically every four to eight weeks. Persistently abnormal results may lead to a dose reduction or a switch to a different medication.