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rheumatology

Methotrexate for Rheumatoid Arthritis: Side Effects Guide

Methotrexate, the most common first-line DMARD for rheumatoid arthritis, is generally well-tolerated. The most frequent side effects — nausea, fatigue around the dose, and hair thinning — are often reduced with folic acid supplementation. Serious liver or lung effects are rare but require regular monitoring.

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Why is methotrexate used for rheumatoid arthritis?

Methotrexate is a disease-modifying antirheumatic drug (DMARD) — meaning it reduces the underlying immune-driven inflammation that causes joint damage in RA, rather than only relieving pain temporarily. The 2021 American College of Rheumatology guideline recommends methotrexate as the preferred initial DMARD for most people with RA, given its effectiveness, long track record, manageable side-effect profile, and low cost 1. The 2022 EULAR update reinforces this position as the anchor drug in RA management 2.

Methotrexate for RA is taken once a week (not daily, as it is used for cancer at much higher doses). It takes several weeks to months to reach its full effect, which is why short-term anti-inflammatory treatment (NSAIDs or a short corticosteroid course) is often used alongside it in the early weeks.

What are the most common side effects?

Nausea and gastrointestinal discomfort are the most frequently reported side effects, typically occurring in the 24–48 hours after the weekly dose 1. Strategies that often help:

  • Taking the dose in the evening, so any nausea occurs during sleep
  • Splitting the dose into two halves taken 12 hours apart
  • Taking methotrexate with food
  • Adequate hydration
  • Folic acid supplementation (see below) — this is one of the most effective approaches 3
  • In persistent cases, switching from oral to injected methotrexate (subcutaneous) is often better tolerated

Fatigue — sometimes called "methotrexate hangover" — is the day-after tiredness that some people experience. This often improves over time or with the same strategies used for nausea.

Hair thinning can occur, typically as diffuse shedding rather than patchy loss. It is usually mild and often reversible if the dose is reduced or folic acid is optimized. Severe hair loss is uncommon 1.

Mouth sores (mucositis): Occasional ulcers inside the mouth can occur. Folic acid supplementation reduces this significantly 3.

What is folic acid and why does everyone on methotrexate take it?

Methotrexate works in part by interfering with folate metabolism in rapidly dividing cells. Folic acid (vitamin B9) supplementation compensates for this, significantly reducing the incidence of nausea, mouth sores, and hair loss without meaningfully reducing the drug's anti-inflammatory benefit 13.

Most rheumatologists prescribe folic acid to be taken on the days when methotrexate is not taken. The typical dose is 1–5 mg daily (except on the day of methotrexate). Some use leucovorin (folinic acid) instead in cases of severe side effects. If you are taking methotrexate without folic acid, ask your clinician about adding it.

What about more serious side effects?

Liver effects: Methotrexate is metabolized by the liver, and long-term use can cause liver inflammation or, rarely, fibrosis. The risk is substantially higher in people who drink alcohol regularly, have pre-existing liver disease, or are obese 1. Regular blood tests (liver function tests every 4–12 weeks initially) are part of standard monitoring 4. Most people on methotrexate should minimize or avoid alcohol.

Lung effects: A rare but serious complication called methotrexate pneumonitis (lung inflammation) can occur 3. Symptoms include a new dry cough, shortness of breath, or fever. Contact your rheumatologist promptly if these develop while on methotrexate — this is not something to wait on.

Bone marrow suppression: In rare cases, methotrexate can lower blood cell counts. CBC monitoring is part of routine follow-up 4.

Infection risk: Methotrexate suppresses the immune system, which can reduce the body's ability to fight infections. It does not carry the same degree of infection risk as high-dose biologics, but live vaccines should not be given while on methotrexate.

Is methotrexate safe to take long-term?

For most people, yes — with proper monitoring 1. Methotrexate has one of the longest and most studied safety track records among RA medications. Decades of real-world use and clinical trial data support its safety profile at the doses used for RA. The key is adherence to monitoring: regular blood tests for liver function and complete blood count allow your rheumatologist to catch any problems early and adjust treatment if needed 4.

Pregnancy: Methotrexate is not safe during pregnancy or while trying to conceive — it is teratogenic (can cause fetal harm). It must be stopped before conception; the recommended washout period should be discussed with your rheumatologist. Reliable contraception is essential during methotrexate use in people who could become pregnant 1.

What if I cannot tolerate methotrexate?

If you cannot tolerate methotrexate despite adequate folic acid supplementation and dose adjustments, other DMARDs are available — hydroxychloroquine, sulfasalazine, leflunomide, and biologic agents 2. Your rheumatologist will choose based on which organs are affected, how active your RA is, your other medical conditions, and your preferences. Do not stop methotrexate without talking to your rheumatologist first — abrupt discontinuation can allow RA to flare.

Common questions

Why is methotrexate taken once a week for RA rather than every day?

The once-weekly schedule for RA is intentional — it reduces toxicity while maintaining efficacy. The anti-inflammatory effect in RA works through mechanisms that are effective with weekly dosing, and more frequent dosing significantly increases the risk of side effects. This is very different from the daily dosing used for cancer, and the two should not be compared directly.

Will my hair grow back if methotrexate causes thinning?

For most people, yes — hair thinning associated with methotrexate is generally reversible if the dose is reduced or folic acid is optimized. Complete hair loss from methotrexate alone (at RA doses) is uncommon.

Can I drink alcohol while taking methotrexate?

Alcohol significantly increases the risk of methotrexate-related liver damage, and rheumatologists generally advise avoiding or minimizing alcohol during methotrexate treatment. Even light drinking warrants a conversation with your clinician. Heavy or regular drinking is a contraindication to methotrexate.

How long does it take for methotrexate to work for RA?

Methotrexate typically takes 4–12 weeks to begin showing effect on joint inflammation, and maximum benefit may not be seen for 3–6 months. During this early period, your rheumatologist may use a short course of corticosteroids or continue NSAIDs to manage symptoms while the DMARD takes hold.

Do I need blood tests while on methotrexate?

Yes. Regular monitoring — including liver function tests and a complete blood count — is a standard and important part of methotrexate use for RA. Frequency is typically higher early in treatment (every 4–8 weeks) and can be spaced out once stable on a dose. Do not skip these monitoring visits.

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Methotrexate: when to contact your care team immediately

  • —New dry cough, shortness of breath, or fever while on methotrexate (possible lung inflammation)
  • —Severe nausea, vomiting, or abdominal pain
  • —Unusual bruising, bleeding, or signs of severe infection
  • —Mouth sores that are preventing eating or drinking
  • —Possible pregnancy or missed period while taking methotrexate — this is urgent

If you are pregnant or become pregnant while taking methotrexate, contact your rheumatologist immediately. If you develop chest tightness, severe shortness of breath, or cough with fever, seek same-day medical evaluation.

This article provides general educational information about methotrexate side effects in the context of rheumatoid arthritis. It does not cover all possible interactions or contraindications. All decisions about starting, continuing, or stopping methotrexate must be made with your rheumatologist.

References

  1. 1.Fraenkel L, Bathon JM, England BR, St Clair EW, Arayssi T, et al. (2021). 2021 American College of Rheumatology Guideline for the Treatment of Rheumatoid Arthritis. Arthritis & Rheumatology. doi:10.1002/art.41752 ✓Methotrexate as preferred first-line DMARD; folic acid co-prescription; liver and CBC monitoring requirements; alcohol avoidance; pregnancy contraindication; dose adjustment strategies
  2. 2.Smolen JS, Landewé RBM, Bergstra SA, et al. (2023). EULAR recommendations for the management of rheumatoid arthritis with synthetic and biological disease-modifying antirheumatic drugs: 2022 update. Annals of the Rheumatic Diseases. doi:10.1136/ard-2022-223356 ✓Methotrexate as anchor DMARD in RA; biologic and targeted synthetic DMARD alternatives when methotrexate insufficient or not tolerated
  3. 3.Onda K, Honma T, Masuyama K (2023). Methotrexate-related adverse events and impact of concomitant treatment with folic acid and tumor necrosis factor-alpha inhibitors: An assessment using the FDA adverse event reporting system. Frontiers in Pharmacology. doi:10.3389/fphar.2023.1030832 ✓Folic acid reduces hepatotoxicity and myelosuppression reporting odds ratios; methotrexate adverse events include interstitial lung disease (ILD), hepatotoxicity, and myelosuppression; ILD as a serious rare complication
  4. 4.National Library of Medicine (2024). Methotrexate Injection: MedlinePlus Drug Information. MedlinePlus. link ✓Requirement for regular laboratory monitoring (liver function, CBC) before, during, and after methotrexate treatment; potential for liver damage, bone marrow suppression, and serious infection risk

4 sources, numbered by first appearance. General health information, not medical advice — synthetic demonstration content.