saudigastro.com/patients/methotrexate-gi
This article is educational and does not replace your doctor's advice. Seek urgent care for any red-flag symptoms.
Drug class
Immunomodulator (antimetabolite)
Examples
Methotrexate (tablets or injection)
How it works
Methotrexate reduces the activity of immune cells that drive inflammation in the gut. Used for IBD, it is given far less often than in cancer treatment, so it is a different and much lower-intensity use. It can take a few weeks to a few months to work.
What it treats
- Keeping Crohn’s disease in remission, especially when other immune-calming medicines are not suitable
- Sometimes added to a biologic medicine to help it keep working
- Other inflammatory conditions (for example arthritis or psoriasis), as decided by your doctor
How to take it
It is taken ONCE A WEEK on the same day, not daily. Taking it daily by mistake can be very dangerous, so check the label and your plan carefully, and ask the pharmacist if you are unsure. Your doctor usually also prescribes folic acid (a vitamin) on a different day to reduce side effects. It may be given as tablets or as an injection under the skin. Your doctor sets the dose; do not change it yourself.
Common side effects
- Nausea, poor appetite or mouth sores (folic acid often helps)
- Tiredness or feeling unwell for a day or two after the weekly dose
- Headache or dizziness
- Mild hair thinning
- Mild rises in liver tests, which are checked with blood tests
Serious side effects — call your doctor
New dry cough, shortness of breath or fever
Rarely the lungs can become inflamed. Seek medical care the same day; go to the emergency department if breathing is difficult.
Fever, chills, sore throat or mouth ulcers that do not heal
May mean low white blood cells or an infection. Contact your doctor the same day.
Yellow skin or eyes, dark urine, or persistent upper-right abdominal pain
Can mean liver injury. Contact your doctor promptly.
Unusual bruising or bleeding, or severe paleness
May mean low blood counts. Contact your doctor promptly; urgent care if bleeding does not stop.
Severe rash, or marked swelling of the face or lips with trouble breathing
Could be a serious allergic reaction. Call emergency services or go to the emergency department now.
Interactions
Some medicines can raise methotrexate levels or add to its effects, including certain antibiotics (such as trimethoprim/co-trimoxazole), anti-inflammatory painkillers (NSAIDs), and some stomach-acid medicines. Always tell every doctor and pharmacist that you take methotrexate before starting anything new, including over-the-counter and herbal products. Alcohol can add to liver strain, so ask your doctor what is safe for you. Avoid live vaccines unless your doctor agrees.
Monitoring
Blood tests (blood count, liver and kidney tests) are done before starting, frequently at first, and then regularly while you take it. Your doctor may also check for hepatitis B and C and for previous chest problems beforehand. Keep all appointments.
When and how to stop
Do not stop or skip doses without speaking to your doctor. It may be paused during an infection or if blood tests change, and it must be stopped well before a planned pregnancy, as advised by your doctor.
Pregnancy & breastfeeding
Methotrexate can cause miscarriage and serious birth defects, so it must NOT be used during pregnancy or breastfeeding. Women who can become pregnant need reliable contraception while taking it, and men and women are both advised to stay off it for a period before trying to conceive; your doctor will tell you how long. If you think you might be pregnant, contact your doctor straight away and do not take another dose until you have spoken to them.
Questions to ask your doctor
Save this list or print it before your appointment — doctors appreciate prepared patients.
- Which day of the week should I take it, and how do I avoid dosing mistakes?
- Should I take folic acid, and on which days?
- How often do I need blood tests?
- What contraception do you recommend, and how long before pregnancy should I stop?
- What should I do if I get an infection or need other medicines?
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Status: Approved for publication by SGA; individual clinician review is ongoing · Published 24/04/2026
For general education only; it does not replace your doctor’s advice. Individual clinician review of this guide is ongoing. SGA clinician? Review this guide