Folic Acid with Methotrexate: What You Need to Know

When you take methotrexate, a drug used to treat autoimmune diseases like rheumatoid arthritis and certain cancers by slowing down overactive immune cells or fast-growing cells. Also known as MTX, it works by blocking folate, a vitamin your body needs to make DNA and repair cells. That’s why doctors often prescribe folic acid, a synthetic form of vitamin B9 that helps your body produce healthy red blood cells and support cell division. Also known as folate, it’s not meant to cancel out methotrexate’s effects—it’s there to protect you from its side effects.

People on methotrexate often get mouth sores, nausea, low blood counts, or liver stress. These aren’t just annoyances—they can make you stop treatment. Taking folic acid daily, usually 1 mg, cuts those side effects by up to 80% in many cases. You don’t need to take it at the same time as methotrexate—most people take folic acid every day except the day they take methotrexate. Some doctors even suggest 5 mg once a week, right after the methotrexate dose. The key? Don’t skip it. Skipping folic acid doesn’t make methotrexate work better—it just makes you sicker.

It’s not just about pills. Folic acid helps your body handle the stress methotrexate puts on your system. If you’re on this combo for rheumatoid arthritis, psoriasis, or even Crohn’s, staying on folic acid means you’re more likely to stick with your treatment long-term. It doesn’t interfere with how well methotrexate fights inflammation or cancer—it just keeps you feeling better while it works. And if you’re worried about getting enough from food? Leafy greens, beans, and fortified cereals help, but they won’t replace the dose your doctor prescribes.

You’ll find posts here that dig into real experiences—how people manage nausea, what blood tests to ask for, why some doctors push folic acid harder than others, and what happens if you forget a dose. There’s no fluff. Just straight talk on what works, what doesn’t, and what to watch for when you’re managing this common but tricky pair.