Who Should Not Take MSM (Methylsulfonylmethane)

MSM rarely causes problems, but that does not mean it is suitable for everyone. The editorial team examined who should avoid the supplement, who needs a doctor's consultation, and who needs only a cautious start.

Why even a "safe" supplement has restrictions

MSM has a reputation as one of the safest supplements for joints, and this reputation is largely deserved: toxicological studies in animals have shown low toxicity, and in clinical studies in humans side effects were mild (Butawan et al., 2017).

However, official contraindications, similar to those specified in the instructions for medicines, have not been formulated for MSM. This does not mean there are none; it means that certain groups of people simply have not been studied.

Therefore the editorial team considers contraindications in three categories: situations where it is better to avoid MSM; situations where intake is possible only after discussion with a doctor; and situations that require a cautious start and observation.

This approach is based on the general principles of safe use of dietary supplements: in the absence of data, caution takes priority, especially for vulnerable groups.

Pregnancy, breastfeeding, and children

There is no data on the safety of MSM during pregnancy in humans. The study by Magnuson and co-authors (2007) in rats found no effect on fetal development even at high doses, but the results of animal studies cannot be directly transferred to humans.

Likewise, there are no studies on the penetration of MSM into breast milk and its effect on the infant. Given that MSM is a small water-soluble molecule that is well distributed in the body, this possibility cannot be ruled out.

Clinical studies of MSM were conducted mainly in adults. For children and adolescents, doses and safety have not been established, and joint pain in childhood always requires examination by a doctor rather than self-administration of supplements.

The editorial team's position: during pregnancy, breastfeeding, and in childhood, it is worth refraining from MSM unless it has been prescribed by a doctor for a specific reason.

Taking medications and chronic diseases

There are no systematic studies of MSM's interactions with medicines. Most often the theoretical effect on blood clotting is discussed, so people who take anticoagulants (for example, warfarin) or antiplatelet agents need a doctor's consultation before starting intake.

MSM is excreted predominantly in the urine (Magnuson et al., 2007), so people with kidney diseases should discuss intake with a nephrologist. Data on people with impaired liver function are also insufficient.

Chronic diseases of the gastrointestinal tract — inflammatory bowel disease, peptic ulcer disease, irritable bowel syndrome — may increase the likelihood of digestive side effects. In these cases, intake should also be agreed with a doctor.

Before planned surgical interventions, doctors often ask patients to stop taking supplements with an unclear effect on blood clotting. MSM formally belongs to this group, so the surgeon and anesthesiologist should be informed about taking it.

Allergy and intolerance: "sulfur" or not

A common question: can people with an allergy to "sulfonamides" or "sulfites" take MSM? These are chemically different substances. Sulfonamide antibiotics contain a specific group to which allergy develops, and sulfites are preservatives in food and wine. MSM belongs to neither the first nor the second group.

Thus, an allergy to sulfonamides or sensitivity to sulfites does not automatically mean a reaction to MSM. At the same time, in people with multiple drug allergies, any new supplement should be introduced cautiously, and better still, after consulting an allergist.

True allergic reactions to MSM are described rarely. If a rash, itching, swelling, or difficulty breathing appears after intake, intake should be stopped immediately and MSM avoided thereafter.

One should also not forget about excipients. A reaction may be caused not by MSM but by a dye, flavoring, the gelatin of a capsule, or another component of the complex.

Athletes and special situations

MSM is not on the WADA Prohibited List, so taking it in itself does not violate anti-doping rules. However, for athletes who undergo doping control, the main risk is contamination of the product by other substances during manufacturing.

Elite athletes should choose products with independent certification for the absence of banned substances and keep the packaging and batch number.

People who sleep poorly should start with morning intake: although the connection between MSM and sleep disturbances has not been proven, individual users report it.

Finally, MSM should not be taken for self-treatment of acute joint pain, swelling, or injury. In these situations the "contraindication" is the delay of diagnosis, not the substance itself.

• Not on the WADA list, but product contamination is possible.
• Certified products are a priority for athletes.
• Acute pain and injury: see a doctor first.

Editorial conclusions

No official contraindications have been established for MSM, but it is worth refraining from intake during pregnancy, breastfeeding, and in childhood due to a lack of data.

People who take anticoagulants or other ongoing medications, have kidney, liver, or digestive tract diseases, or are preparing for surgery need a prior doctor's consultation.

An allergy to sulfonamides or sulfites is not an automatic contraindication, but any reaction to MSM is a reason to give it up.

Also read: "Side Effects of MSM," "How to Take MSM," and "Myths About MSM."

References

1. Butawan M, Benjamin RL, Bloomer RJ. Methylsulfonylmethane: applications and safety of a novel dietary supplement. Nutrients. 2017;9(3):290.
2. Magnuson BA, Appleton J, Ryan B, Matulka RA. Oral developmental toxicity study of methylsulfonylmethane in rats. Food Chem Toxicol. 2007;45(6):977–984.
3. Magnuson BA, Appleton J, Ames GB. Pharmacokinetics and distribution of [35S]methylsulfonylmethane following oral administration to rats. J Agric Food Chem. 2007;55(3):1033–1038.
4. Horváth K, Noker PE, Somfai-Relle S, et al. Toxicity of methylsulfonylmethane in rats. Food Chem Toxicol. 2002;40(10):1459–1462.
5. World Anti-Doping Agency. The 2025 Prohibited List: International Standard. Montreal: WADA; 2025.