Dimethyl fumarate is an oral medication prescribed for the treatment of multiple sclerosis (MS) symptoms. It’s sold in capsule form, under the brand name Tecfidera. Dimethyl fumarate is approved for use in the United States as a treatment for relapsing forms of MS. It helps decrease the frequency of MS relapses, which may delay or prevent permanent nerve damage that can lead to disability.

This medication also was shown to improve everyday functioning in one of the approval trials. The improvement was measured as a decrease in disability progression. However, this disability decrease wasn’t seen in the other trial upon which the FDA based their approval decision.

This medication is an Nrf2 activator, a type of drug that decreases inflammation (swelling). The exact mechanism of action leading to the observed clinical improvements in MS patients is unknown. Dimethyl fumarate is also used  to control skin inflammation in some psoriasis patients, but this use is not approved in the United States.

How to Take Dimethyl Fumarate

Dimethyl fumarate is a capsule taken twice a day. It’s important to take it around the same times each day. This regularity helps ensure that the medication will work as it’s supposed to. Take it every 12 hours for best results. If you miss a dose, don’t double up on capsules to make up for it. Instead, take the medication as soon as you remember to.

Your doctor will likely start you on the lowest dose possible, and gradually will increase the dosage each week. The National Multiple Sclerosis Society outlines a typical dosing schedule as follows:

  • week one: 120 mg, twice a day
  • week two: 240 mg, twice a day

The first week’s administration is called a “starter dose.” It contains half the dose of a regular prescription. The purpose of the 120 mg starter dose is to get your body accustomed to the medication and also to prevent flushing side effects.

Take dimethyl fumarate with food to decrease the risk of flushing. Be sure to swallow the capsules whole—don’t crush or break them.

Common Side Effects

You may experience side effects during the first few weeks of taking dimethyl fumarate. These are generally mild and go away without requiring additional medical attention. Call your doctor if your side effects are severe, or last longer than a month.

The most common side effects include:

  • flushing (which may include skin warmth, redness, itching, and burning)
  • nausea and vomiting
  • heartburn
  • abdominal pain
  • diarrhea

Dimethyl fumarate can also worsen a preexisting infection. Therefore, you should not start this medication if you’re fighting an infectious illness.

Important Tests Before Starting This Medicine

Your doctor will order certain tests before ordering your prescription. A blood cell count will be required in order to measure your level of white blood cells (lymphocytes). The National Multiple Sclerosis Society says that a blood cell count performed within the last six months is acceptable for this purpose. It is recommended that you get an annual blood cell count test while taking dimethyl fumarate.

Long-Term Risks

One of the biggest concerns associated with dimethyl fumarate is its ability to reduce white blood cell count. An adequate amount of white blood cells are needed to help prevent infections. According to the National Multiple Sclerosis Society, no reports of serious infections have been associated with this particular MS medication.

According to the World Journal of Neurosciences, the John Cunningham Virus (JCV) is unknowingly carried by 70 to 90 percent of the world's population. Immunosuppressive drugs can cause an increased risk of awakening the virus and developing an active infection. Having a depressed immune system also increase the risk of catching JCV even if you aren't already a carrier.

Dimethyl fumarate may weaken the immune system enough to allow the JCV virus to re-awake or increase the chances of catching the virus from someone else. Having an active JCV infection can increase the risk of developing progressive multifocal leukoencephalopathy (PML). PML may occure if JCV is carried to the brain. There, JCV may infect the white matter of the brain and attack the cells responsible for making myelin. If PML develops is can be disabling, even fatal.

Dimethyl fumarate has been found to increase liver enzyme levels in some patients. However, there have been no reports of serious liver toxicity. Discuss any concerns you may have with your doctor.


There is no cure for MS, but dimethyl fumarate decreases the frequency of active disease episodes in some patients. It may also possibly ease your symptoms and improve your quality of life.

Dimethyl fumarate works best for patients with recurring MS symptoms, and is designed for long-term use. Taking it regularly can help reduce incidents of muscle spasms and nerve damage.

It’s best to talk to your doctor about all treatment options, as well as your medical history, so the two of you can decide which treatment approach is best for you.