Used with other medicines: Dose is based on body size and must be determined by your doctor. The dose is usually 10 mg per meter squared (m (2)) of body size 2 times a week. NHS medicines information on dosage for methotrexate, how to take it and what to do if you miss a dose or take too much. The standard methotrexate dosage for rheumatoid arthritis is 7.5-25 mg per week. Use our methotrexate dosage chart to find the recommended and maximum doses of methotrexate. Concomitant administration of NSAIDs with high dose methotrexate has been reported to elevate and prolong serum methotrexate levels, resulting in deaths from severe hematologic and GI. Detailed Methotrexate dosage information for adults and children. Includes dosages for Rheumatoid Arthritis, Psoriasis, Breast Cancer and more; plus renal, liver and dialysis adjustments. For healthy adults with rheumatoid arthritis, start methotrexate at 7.5-15 mg orally once weekly, with rapid escalation to at least 15 mg weekly within 4-6 weeks to optimize efficacy. 1 Taking more methotrexate than prescribed or taking methotrexate more often than prescribed can lead to severe side effects and cause death. If you are not sure how often to take methotrexate, ask your healthcare provider or pharmacist. Methotrexate is prescribed for autoimmune conditions, certain cancers, and ectopic pregnancies, with a unique dosage of once weekly to prevent toxicity. Understanding the correct usage of methotrexate is crucial for its effectiveness and safety. Methotrexate dosage and administration guide from FDA labeling. How to take, recommended doses, and forms available. • ALL: The recommended dosage is 20 mg/m2 orally once weekly as a part of a combination chemotherapy maintenance regimen. (2.2) • Mycosis fungoides: The recommended dosage is 25 to 75 mg orally.