MSM (methylsulfonylmethane) side effects reported so far include an upset stomach, diarrhea, and in one small trial, insomnia. A 2015 presentation by a compounding-industry nominator (PCCA) to the FDA’s Pharmacy Compounding Advisory Committee quotes FDA briefing information saying the safety profile of MSM is poorly characterized and that MSM may interact with warfarin and raise bleeding risk, so check with your prescriber or pharmacist before you combine it with any blood thinner.
What is MSM?
MSM is an organic compound that contains sulfur. Medical News Today’s MSM overview explains that MSM is not sulfur in itself, but a compound that holds the same sulfur found in the body and in foods such as vegetables, fruit, grains and meat. Most supplements contain a synthetic form, and the compound is also called dimethyl sulfone. People usually take MSM for joint pain, muscle recovery after exercise and allergy relief.
What is MSM in skin care?
In skin care, MSM appears in creams and in a few studies of aging skin. The best-known skin study used hairless mice. Researchers exposed the mice to UVB light and injected MSM into their skin rather than applying it as a cream. The wrinkle score was 2.5 in mice given UVB alone and 1.8 in mice given MSM. The authors conclude that MSM injection reduced wrinkle scores in these mice. The hairless mouse skin study is an animal injection study, not a cream trial in people.
Rootine, a supplement brand, says MSM’s studied uses include treating scars, wrinkles and stretch marks. That is the brand’s own claim. Medical News Today notes that medical studies of MSM for skin are limited, while dermatologists have long prescribed sulfur creams, which are a different form of sulfur.
If you use an MSM cream, Medical News Today advises choosing a product that states how much MSM it contains and how often to apply it. If you already use a prescription cream for rosacea or another skin condition, ask your dermatologist before you add MSM cream.
Is MSM safe for human consumption?
MSM has a food-safety history in the US. A 2008 reply to a GRAS notice (generally recognized as safe) from the FDA’s food safety center said it had no questions about the submitter’s conclusion that MSM is GRAS for certain foods. Those uses included meal supplements, smoothie-type drinks and thirst-quencher beverages up to 4,000 mg/kg, and food bars up to 30,000 mg/kg. This is quoted in the 2015 advisory committee presentation on MSM by a compounding-industry nominator (PCCA).
The same presentation is more cautious about long-term use. Quoting FDA briefing information, it says the safety profile of MSM “is poorly characterized,” and that there are “no safety data to indicate whether risk increases over time.” Rootine states that the FDA has labeled MSM GRAS; the 2008 letter in that presentation covered only the food uses listed above and was not a general label.
What are the side effects of MSM?
Side effects reported in the sources include mild digestive effects, such as upset stomach and diarrhea, and insomnia in one small trial. The nominator presentation, quoting FDA briefing information, says the safety profile of MSM is poorly characterized. The table lists each report and where it comes from.
| Side effect | Where it was reported | Source |
|---|---|---|
| Upset stomach or diarrhea | Arthritis Foundation, as reported by Medical News Today | Medical News Today |
| Nausea, diarrhea, fatigue, insomnia | Rootine says side effects in human trials were mild, among others | Rootine article (brand’s own claim) |
| Mild gastrointestinal effects; one case of insomnia | Two MSM participants reported mild GI effects and one reported insomnia in the Portland Half-Marathon trial, which used 3 g/day | Randomized, double-blind, placebo-controlled trial |
| No special side effects with injection (mice) | The authors report no special side effects in the mice, even when MSM was injected. | Hairless mouse study |
| Shrinkage of several organs, including the liver and spleen | Rats given 100 times the standard human dose, in a 2013 study as Medical News Today reports it | Medical News Today |
In the Portland trial, one placebo participant also dropped out after reporting low energy and difficulty concentrating. The trial listed no side effects for the placebo group, so keep that in mind when you read side effect lists.
What should you not mix with MSM?
The main concern is bleeding with blood thinners. The nominator presentation to the FDA advisory committee describes this interaction, quoting FDA briefing information.
| Medicine or condition | What the sources document | What to do |
|---|---|---|
| Warfarin | The nominator presentation, quoting FDA briefing information, says literature and a database search suggest “there may be an interaction with warfarin and risk for bleeding, even with relatively short-term exposure.” | Ask your prescriber or pharmacist before combining. |
| Blood thinners in general | Medical News Today reports that the Arthritis Foundation advises people who take blood thinners to avoid MSM. | Ask your prescriber before you start. |
| Anticoagulants | The FDA briefing information quoted in the presentation describes “a potentially serious interaction with anticoagulants and risk of bleeding.” | Ask your pharmacist to check your full medicine list. |
| Blood pressure | The FDA briefing information quoted in the presentation lists “a risk for hypertension,” from literature only. | Tell your prescriber if you start MSM and track your readings. |
| Glucosamine, chondroitin, NSAIDs | The nominator presentation lists these as typical combination therapies and says screening for drug-drug and drug-nutrient interactions is “the standard of care.” | Have your pharmacist review every product you take. |
The Portland trial excluded people taking warfarin, corticosteroids or statins, so it does not show how MSM affects those users.
What should you avoid when taking MSM?
- Taking more than directed. Medical News Today reports that taking more MSM than directed does not appear to give better results. In the 2018 allergy study, people taking 12 g had less allergy relief than those taking 3 g.
- Blood thinners without a check. See the table above.
- Pregnancy, breastfeeding and children. Medical News Today says pregnant or breastfeeding people, children, and people with health conditions should speak with a doctor before taking MSM.
- Long-term use without a review. One study suggests MSM levels in the body may build up over time. Ask your prescriber how long to continue.
What happens if you take MSM every day?
Most trials used a set daily amount. The Portland trial gave 3 g/day from three weeks before a race until two days after it. The 2021 trial of 22 adults with overweight or obesity gave 3 g daily for 16 weeks. Medical News Today describes a 26-week study of adults with hip or knee osteoarthritis that used 6 g/day. These are trial amounts, not a recommended intake for you.
In the 2021 randomized MSM trial, serum MSM rose significantly by 4 weeks and did not differ between weeks 4 and 16. The authors write that more prolonged intake studies would show whether regular use leads to steady serum concentrations. Long-term safety data remain limited, so ask your prescriber or pharmacist how long you should take it.
What does MSM do to your brain?
The nominator presentation says that “significant levels of MSM are present in the brain following oral administration in humans and rats.” It adds that the clinical significance of this is uncertain, because oral toxicity data are limited.
In humans, the presentation describes a 2001 review of four patients, three of whom were examined once, using chart review and magnetic resonance spectroscopy (MRS). It reports: “No adverse clinical or neurochemical effects were observed.” The presentation also reports that MSM readily crosses the blood-brain barrier in rats and that toxicology data are limited.
Does MSM affect the liver or kidneys?
Liver and kidney effects of long-term MSM use in people are not well documented. The only organ-damage finding in the sources here comes from the rat study at 100 times the human dose, which is listed in the side effects table. If you have liver or kidney disease, ask your prescriber before you start and bring a list of your current medicines.
Is MSM good for diverticulitis?
MSM has been studied for joint pain, exercise soreness, allergy, skin, and metabolic markers. Diverticulitis is not on that list. If you have diverticulitis, ask your gastroenterologist or pharmacist whether MSM makes sense before you add it.
What are the side effects of glucosamine, chondroitin, and MSM together?
The nominator presentation names glucosamine and chondroitin as typical combination therapies with MSM for osteoarthritis. For the side effects of glucosamine and chondroitin themselves, read the label of the product you are considering or ask a pharmacist. Side effects of the combination may include those of each part, so review the full list with your pharmacist.
What is MSM claimed to do, and what did studies find?
| Use | What the studies found | Source |
|---|---|---|
| Joint pain and osteoarthritis | A 2018 meta-analysis found MSM may improve osteoarthritis symptoms in the short term, but its clinical importance was not clear. The Arthritis Foundation states there are currently no large, well-controlled studies on MSM. | Medical News Today |
| Exercise soreness | In the Portland trial of 22 runners, pain was lower in the MSM group at every post-race time point, but group comparisons did not reach statistical significance. | Portland Half-Marathon trial |
| Allergy | Medical News Today reports that the 2018 allergy study found people taking 12 g had less relief than those taking 3 g. | Medical News Today |
| Skin aging | Injection in hairless mice reduced wrinkle scores. No human skin trial of MSM is described in these sources. | Hairless mouse study |
| Heart and metabolic markers | In the 2021 trial, HDL cholesterol was higher than baseline at 8 and 16 weeks in the MSM group, but the difference between MSM and placebo was not significant. Fasting glucose and insulin sensitivity did not change. CRP was lower than placebo because it rose in the placebo group. | 2021 randomized MSM trial |
Is there MSM weight loss research?
The 2021 trial’s stated aim was to determine whether MSM improves cardiometabolic health, and markers of inflammation and oxidative status. Its sample was small, which the authors say limits interpretation. Weight-loss promises you see in ads or reviews are the seller’s claim, not a result this trial set out to measure.
Are magnesium and MSM the same thing?
No. MSM contains sulfur, and magnesium is a separate supplement with its own safety rules. Cleveland Clinic’s magnesium article says magnesium supplements are generally safe at recommended doses, but taking more than 350 mg per day from supplements can cause diarrhea, nausea and stomach cramps. It also notes interactions with certain antibiotics, osteoporosis medicines and diuretics.
What food is high in MSM?
No food is named as a high source. Medical News Today lists fresh vegetables, meat and dairy products as natural sources, and Rootine adds tea, coffee and milk, in small quantities. Food is not a practical way to reach a supplement-level amount.
Checklist before you use MSM
- Compare: the amount of MSM per serving and how often to take it, as listed on the label. Medical News Today advises choosing a product that states both.
- Track: your daily amount, any stomach upset or diarrhea, sleep changes, and any unusual bruising or bleeding.
- Bring: a full list of your medicines, including blood thinners, and any history of kidney or liver problems.
- Ask: whether MSM fits with your medicines, how long to take it, whether glucosamine or chondroitin should be included, and which symptoms mean you should call the office.
For other products’ side effect and safety checks, see the vardenafil guide and the PT-141 guide.
By the Integrative Health Evidence Guide Team
This article is for general information purposes only and does not constitute medical advice. Consult your doctor or qualified healthcare provider before making changes to your health routine.