Methotrexate is usually taken as a single dose once per week, although occasionally the dose is split into two to improve absorption or avoid side effects. Your doctor also may prescribe a folic acid (or folate) supplement to decrease the chance of side effects. 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. 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. 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. NHS medicines information on dosage for methotrexate, how to take it and what to do if you miss a dose or take too much. For both rheumatoid arthritis and psoriasis, methotrexate should be administered at a weekly dosage ranging from 7.5 mg to 25 mg, with individualized titration based on clinical response and tolerability. 1, 2 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. Follow applicable special handling and disposal procedures.1. The recommended starting dosage of Methotrexate Tablets is 20 mg/m2 orally once weekly, as part of a combination chemotherapy. Detailed Methotrexate dosage information for adults and children. Includes dosages for Rheumatoid Arthritis, Psoriasis, Breast Cancer and more; plus renal, liver and dialysis adjustments. 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.