Updated: March 26, 2026

What Is Methotrexate? Uses, Dosage, and What You Need to Know in 2026

Author

Peter Daggett

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What Is Methotrexate?
What Conditions Does Methotrexate Treat?
Autoimmune and Inflammatory Diseases
Cancer (Oncology Uses)
What Formulations Does Methotrexate Come In?
How Is Methotrexate Dosed?
Key Safety Facts

Methotrexate treats both cancer and autoimmune diseases, but how it works and how it's taken are very different. Here's everything you need to know about methotrexate in 2026.

Methotrexate is one of medicine's most versatile drugs — and one of its most misunderstood. It's both a chemotherapy agent and an immunosuppressant, used in doses that differ by 100-fold depending on the condition being treated. If you or a loved one has been prescribed methotrexate, here's what you need to know.

What Is Methotrexate?

Methotrexate (MTX) is a folic acid antagonist — a drug that interferes with folic acid metabolism in cells. It was first developed in the 1940s as a cancer treatment and received FDA approval in 1953. Today it remains one of the most widely prescribed medications worldwide for both oncology and autoimmune diseases.

The brand name Rheumatrex is discontinued; methotrexate is now available only as a generic. The subcutaneous auto-injector RediTrex remains available for RA and psoriasis patients who prefer an injectable route.

What Conditions Does Methotrexate Treat?

Methotrexate has FDA-approved indications for a wide range of conditions:

Autoimmune and Inflammatory Diseases

Rheumatoid arthritis (RA): Methotrexate is the gold-standard first-line DMARD for RA worldwide. It reduces joint inflammation, slows disease progression, and decreases joint damage on X-rays.

Polyarticular juvenile idiopathic arthritis (JIA): FDA-approved for children with multi-joint arthritis

Severe plaque psoriasis: For patients who don't respond to topical treatments or phototherapy

Psoriatic arthritis: Treats both joint and skin components of psoriatic disease

Cancer (Oncology Uses)

Acute lymphoblastic leukemia (ALL) — one of the most common childhood cancers

Non-Hodgkin's lymphoma

Osteosarcoma (bone cancer) in children and young adults

Breast cancer, head and neck cancers, lung cancer, bladder cancer

Choriocarcinoma and other gestational trophoblastic diseases

What Formulations Does Methotrexate Come In?

Oral tablets: 2.5 mg scored tablets; used for RA, psoriasis, and some cancer regimens

Injectable solution (25 mg/mL): Available in 2 mL, 10 mL, and 40 mL vials; used for cancer treatment and subcutaneous injection for RA

Subcutaneous auto-injector (RediTrex): 15 mg, 20 mg, 25 mg prefilled pens for RA and psoriasis

How Is Methotrexate Dosed?

This is one of the most important things to understand about methotrexate: doses vary enormously depending on the condition being treated.

RA and psoriasis (low dose): 7.5–25 mg taken ONCE WEEKLY. This is critical — this dose is taken weekly, not daily.

Juvenile idiopathic arthritis: 10 mg/m² once weekly, adjusted by weight and response

Cancer (high dose): Doses range from several hundred mg to several grams per m², administered by IV in hospital settings with leucovorin rescue

⚠️ Fatal dosing errors: Deaths have been reported when patients took their weekly RA dose daily by mistake. Always confirm your dosing schedule with your doctor.

Key Safety Facts

Not a controlled substance: No DEA schedule; any licensed prescriber can write for it

Contraindicated in pregnancy: Causes birth defects and fetal death; women of childbearing age need contraception during and for 6 months after stopping

Regular monitoring required: CBC and liver function tests every 1–2 weeks initially, then every 2–3 months while stable

No alcohol: Alcohol significantly increases the risk of liver damage with methotrexate

Curious about how methotrexate works at the cellular level? Read our post on how methotrexate works — mechanism of action explained. If you're having trouble finding methotrexate at your pharmacy, medfinder can help you locate it near you.

Frequently Asked Questions

Methotrexate is most commonly prescribed for rheumatoid arthritis, where it is the standard first-line disease-modifying antirheumatic drug (DMARD). It is also widely used for psoriasis, psoriatic arthritis, juvenile idiopathic arthritis, and a range of cancers including leukemia, lymphoma, and osteosarcoma.

At high doses, yes — methotrexate is used as a chemotherapy agent for cancer treatment. At the much lower doses used for rheumatoid arthritis and psoriasis (7.5–25 mg once weekly), it is classified as a disease-modifying antirheumatic drug (DMARD) and immunosuppressant rather than traditional chemotherapy.

For rheumatoid arthritis, most patients begin to notice clinical improvement within 3–6 weeks of starting methotrexate. Maximum benefit typically takes 3–6 months to achieve. Most studies show clinically meaningful improvement within 12 weeks. Regular monitoring is needed during this initiation period.

For non-cancer conditions like RA and psoriasis, methotrexate is taken once weekly because daily dosing causes severe, potentially fatal toxicity — including bone marrow suppression, GI hemorrhage, and liver failure. Weekly dosing provides therapeutic benefit while allowing cells to recover between doses. This is a key patient safety point emphasized in the drug's boxed warning.

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