Epsom Salt Taken by Mouth as a Laxative: Risks

Urgent warning. Too much magnesium can slow the heart and breathing, as one case report describes. [1] If someone has swallowed Epsom salt and has extreme weakness, confusion, a very slow pulse or trouble breathing, call 911. For any swallowing question, call Poison Help at 1-800-222-1222. Signs of excess magnesium described in a toxicology report include extreme muscle weakness, loss of deep tendon reflexes, depressed mental state and abnormal heart rhythms. [2] This page gives no amounts and no instructions.

What the product is

Epsom salt is primarily magnesium sulfate, and in the products we read it is used as a saline (salt-type) laxative. [1] [3] On DailyMed, the National Library of Medicine's drug-label database, over-the-counter Epsom salt labels list "occasional constipation" as the use. [3] A label is the maker's statement of intended use, listed in a federal database. It is not proof that a product is safe for you. Bath use is covered separately in Epsom Salt Baths for Muscle Soreness and Sleep.

What the evidence says it does

Proper evidence not found for trials of Epsom salt itself for constipation. We searched PubMed for magnesium sulfate with oral, constipation and trial terms and found no adult trial of Epsom salt for constipation. A 2021 systematic review of over-the-counter chronic constipation therapies found moderate evidence for magnesium-based products as a group, with diarrhea, nausea, bloating and abdominal pain common and no serious adverse events reported. [4] The abstract does not say which magnesium salts were tested, so it cannot be applied to Epsom salt specifically. For wider options see Constipation: What Helps and When to Get Checked.

What drug labels warn

Two Drug Facts labels for Epsom salt on DailyMed say:

• Kidney disease and magnesium-restricted diets: ask a doctor before use if you have kidney disease or a magnesium restricted diet. [5]
• Other symptoms: ask a doctor before use if you have stomach pain, nausea or vomiting, or a sudden change in bowel habits lasting more than 2 weeks. [5]
• Medicines: ask a doctor or pharmacist if you take prescription drugs; one label says the laxative may affect how other drugs work. [3]
• Duration: stop and ask a doctor if you need a laxative for more than 1 week or have rectal bleeding or no bowel movement after use. [5]
• Pregnancy and breastfeeding: ask a health professional before use. [5]
• Overdose: get medical help or contact a Poison Control Center right away. [5]

The NHS gives similar general advice for laxatives bought without a prescription: do not use them for longer than 7 days. [6] It lists heart conditions and being pregnant or breastfeeding among reasons to check with a pharmacist or doctor first, and notes that its list of laxatives is not complete. [6]

Documented harms

Reports like these are individual cases, not rates. A 1996 report notes clinically significant high magnesium after oral or rectal magnesium products in people with normal kidney function is rare. [2] MedlinePlus says excess magnesium most often occurs with supplement forms or laxatives that contain magnesium, and mostly affects people with significantly reduced kidney function. [10]

Who should be most careful

• Kidney disease: named on the labels above and by MedlinePlus. See Kidney Disease and Supplements.
• Children: one fatal case involved a child and an enema. [9] See Natural Ingredients for Babies and Children.
• Medicines: see How Interactions Work.
• Older adults, liver disease, allergy, pre-surgery (for example bowel preparation): not described in the sources we read, so we make no claims. Tell the surgical team about any laxative or supplement you use.

What a reader can safely do

Ask a pharmacist or clinician before using any laxative, especially with kidney disease, heart disease, pregnancy or regular medicines. See a clinician for constipation that lasts, or comes with pain, vomiting or bleeding. The broader Epsom salt picture is in Epsom Salt: Baths, Magnesium Absorption and Safety.