If you or someone you love is living with rheumatoid arthritis, psoriatic arthritis, or another autoimmune condition, there’s a good chance you’ve heard of methotrexate. It’s one of the most commonly prescribed medications in rheumatology, and while effective, it often brings up a few important questions—especially why it’s only taken once a week.

What Is Methotrexate?

Methotrexate is a medication with a history that goes back over 40 years. Originally used in high doses for chemotherapy, it’s now a low-dose, highly effective treatment for autoimmune diseases like rheumatoid and psoriatic arthritis. It belongs to a class of drugs known as DMARDs—disease-modifying anti-rheumatic drugs—which help slow or stop the immune system from attacking the joints.

In these conditions, your immune system becomes overactive and targets healthy joints, causing pain, swelling, and long-term damage. Methotrexate helps reduce that immune attack.

Why Is Methotrexate Taken Once a Week?

Unlike most medications that are taken daily, methotrexate is prescribed just once a week. This once-weekly dosing is key for both safety and effectiveness.

Methotrexate works by slowing down the growth of cells, especially immune cells. If taken daily, even at low doses, the medication can accumulate and become toxic. Weekly dosing allows enough time between doses for your body to process the drug safely while still controlling inflammation effectively.

This schedule also reduces the risk of serious side effects and helps protect your liver and other organs. It’s critically important to never take methotrexate daily unless specifically instructed—doing so can be dangerous and even life-threatening.

How Is Methotrexate Taken

Methotrexate can be taken in two ways:

• Orally (by pill)

• By injection under the skin (similar to an insulin shot)

The injectable form may be used if the oral form causes side effects like nausea or if the oral dose isn’t providing enough benefit.

What Are the Side Effects?

Like all medications, methotrexate has potential side effects. Common ones include:

• Nausea or upset stomach

• Fatigue the day after taking it

• Mouth sores

• Hair thinning

• Low white blood cell count (rare)

To reduce these risks, most patients take folic acid, a B vitamin that helps protect healthy cells from methotrexate-related side effects. Folic acid is typically taken daily.

More serious side effects—though less common—can include liver damage, lung inflammation, increased infection risk, and birth defects if taken during pregnancy. This is why routine blood tests and close medical monitoring are essential.

Is It Chemotherapy?

Technically, yes—but not in the way many people think. At high doses, methotrexate is used for cancer treatment. In rheumatology, we use much lower doses. The goal isn’t to destroy cells but to gently calm an overactive immune system. Think of it like the difference between a race car and a regular car—they may share components, but they’re used very differently.

When Will You See Results?

Methotrexate isn’t an overnight fix. It typically takes 4 to 8 weeks to start working. In the meantime, other treatments like short-term steroids or anti-inflammatory medications may help manage symptoms.

Can You Stop Methotrexate Later?

Yes, some patients go into remission. If your symptoms remain controlled over time, your doctor may gradually reduce your dose—or even stop it—if it’s safe to do so.

Are There Alternatives

Yes, other options include biologic medications and JAK inhibitors. However, methotrexate is often the first choice because it’s affordable, well-studied, and can enhance the effects of other treatments when used together.

Conclusion

Methotrexate is a time-tested, effective treatment for autoimmune arthritis. Taken weekly, it balances safety and results when monitored carefully. If you’re starting methotrexate or already using it, understanding how it works is the first step toward managing your condition confidently.

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