Contraindications of milk thistle

Updated February 21, 2017

Milk thistle (Silybum marianum) is a common alternative medicine for patients who have liver or digestive complaints. Although generally considered safe, it does have some contraindications. A contraindication is a circumstance in which taking a medication may cause harm. This circumstance may be an existing health condition that makes the use of milk thistle hazardous, or a drug or supplement that interacts negatively with milk thistle.

Drug Interactions

According to the University of Maryland Medical Center, milk thistle can interfere with medications that are broken down by the same liver enzyme, which include common drugs for allergies, anxiety, cancer, and high cholesterol, as well as certain blood thinners.

Milk thistle may also interfere with certain antipsychotic and anti-seizure medications.

Always consult your medical professional before taking milk thistle or other supplements.

Pre-existing Conditions

People who are pregnant, lactating or suffering from severe liver disease should not begin a regimen of milk thistle. Patients with existing gastrointestinal maladies---including nausea, diarrhoea, bloating, abdominal pain, and gas---should not use milk thistle unless advised by a physician.

Individuals who are allergic to ragweed, artichokes, kiwi, the aster family, or common thistle should avoid the use of milk thistle.

The use of milk thistle is contraindicated for people who have been diagnosed with uterine fibroids, endometriosis, or uterine, breast or ovarian cancer.

Adverse Effects

One of the major components of milk thistle is silymarin, which is known to increase bile secretions by stimulating the liver and gall bladder. This increase in bile may have a mild laxative effect for two or three days. Other possible side effects of milk thistle include headache and rash.

Taking too much milk thistle may cause changes to the female user's menstrual cycle.

Milk thistle may decrease blood glucose levels in diabetics, which may interfere with pre-existing therapy for hypoglycaemia or hyperglycaemia. In these instances, caregivers should carefully monitor the patient's blood glucose levels.

A small number of milk thistle users have reported symptoms like loss of appetite, gas, heartburn, joint pain and impotence. Although milk thistle may not have caused these symptoms, you should always report any unusual symptoms to your doctor while taking milk thistle or other supplements.

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About the Author

Based in eastern Virginia, Cathy Welch began writing nonfiction articles and novels in 1996. She wrote a short story that appears in John Maxwell’s “Everyone Communicates, Few Connect.” She writes reviews and nonfiction for Longridge Writer’s Group. Welch holds a Bachelor of Science in business administration from Christopher Newport University with a concentration in management.