Can Milk Thistle & Red Clover Be Taken Together?

Milk thistle is most often used to treat liver complaints, while red clover is used in folk medicine for many reasons, including premenstrual syndrome, menopausal complaints, high cholesterol, cancer prevention, indigestion, coughs, bronchitis and asthma. Both herbs have side effects and interact with medications and other herbs. Taking them together raises your risk for unwanted effects. Consult a doctor before using either herb.

Estrogenic Effects

Both milk thistle plant and red clover have estrogenic effects in your body. Taking them together magnifies these effects. Consult a doctor before taking either herb if you have a hormone-sensitive condition such as uterine cancer, breast cancer, ovarian cancer, uterine fibroids, endometriosis or prostate cancer. Also use caution when combining these herbs with estrogen pills, contraceptives, hormone replacement therapy or other medications used to treat hormone-sensitive conditions. Milk thistle seeds do not appear to have the same estrogenic effects as milk thistle plant, notes National Institutes of Health online medical encyclopedia Medline Plus.

Drug Metabolism

Both milk thistle and red clover can decrease the rate at which your liver breaks down certain medications. Specifically, both herbs can increase side effects and effects of medications changed by cytochrome P450 2C9, or CYP2C9, substrates. Taking them together may increase this effect. Some of these medications include warfarin, amitriptyline, losaran, diazepam, zileuton, ibuprofen, celecoxib, diclofenac, irbesartan, fluvastatin, glipizide, phenytoin, piroxicam, tolbutamide and torsemide. Consult your doctor before taking either herb with a medication that is broken down in your liver.

Tamoxifen Effects

Milk thistle may increase how much tamoxifen, a drug used to treat and prevent estrogen-sensitive cancers, is absorbed by your body. Red clover, meanwhile, appears to decrease effectiveness of tamoxifen, according to Medline Plus. Do not take red clover if you use tamoxifen, and consult a health-care provider before combining tamoxifen and milk thistle.

Side Effects

Red clover and milk thistle have many of the same side effects, so taking them together raises risk for such effects. These include nausea, vomiting and menstrual changes. Red clover also can cause rashes, muscle aches and headaches. Milk thistle also may have a laxative effect and cause appetite loss, bloating, indigestion, intestinal gas and fullness or pain.