Methotrexate Guide — what you need to know to use it safely

Methotrexate is a common and powerful medicine used for rheumatoid arthritis, psoriasis, and certain cancers. It works well, but it can also cause serious side effects if not managed right. This guide gives clear, practical steps you can use now — how it’s taken, what labs you’ll need, common warnings, and when to call your healthcare team.

Dosing and monitoring

Methotrexate dosing depends on the reason you’re taking it. For autoimmune diseases like rheumatoid arthritis, low-dose methotrexate is usually given once weekly by mouth or injection. For cancer, doses are higher and schedules vary. Never take a weekly dose daily — that mistake can be dangerous.

Your provider will order baseline and routine tests: complete blood count (CBC), liver function tests (ALT/AST), and kidney function (creatinine). Early checks are typically every 2–4 weeks when starting or changing dose, then every 1–3 months once stable. If your liver tests or blood counts change, your doctor may lower or stop the medicine.

Folic acid is commonly prescribed with methotrexate. It reduces mouth sores, nausea, and some blood effects. Take folic acid as your provider recommends — usually daily except the methotrexate day, but follow their plan.

Safety tips and common questions

Watch for red flags: fever, sore throat, unusual bruising or bleeding, severe mouth sores, persistent cough, or yellowing skin. These can signal bone marrow suppression, infection, or liver injury. Stop the drug and contact your provider immediately if you have these symptoms.

Don’t drink alcohol regularly while on methotrexate. Alcohol increases liver stress and raises the chance of liver damage. Ask your doctor how much, if any, is safe for you.

Drug interactions matter. Common culprits include trimethoprim-sulfamethoxazole, some NSAIDs, and certain antibiotics. Tell every prescriber and your pharmacist that you take methotrexate before starting new meds.

If you miss a weekly dose, call your provider. Do not double up to make up for a missed dose. For injectable methotrexate, learn safe injection technique and where to store supplies.

Methotrexate can harm a pregnancy. Women and men should discuss contraception before starting treatment. If you’re planning pregnancy, talk to your specialist well before stopping the drug — stopping suddenly without guidance isn’t ideal. Live vaccines are usually avoided while on methotrexate; inactivated vaccines are safer but ask your provider for a plan.

Travel or surgery? Bring a note that lists methotrexate and recent lab results. For minor surgery or dental procedures, your team may advise temporarily holding the drug.

Simple steps reduce risk: keep lab appointments, take folic acid, avoid regular alcohol, report new symptoms fast, and tell every clinician you see about methotrexate. When used carefully, methotrexate helps many people stay active and control disease. If anything feels off, call your clinic — quick action prevents problems.