Fenugreek has been used for centuries as a dietary supplement and herbal remedy, but the medicinal uses of the herb are not entirely free of risk. Reports of fenugreek side effects range from minor gastrointestinal discomfort or skin iritation to serious conditions such as internal bleeding. When present, the side effects of fenugreek usually are mild and include symptoms such as nausea, diarrhea, heartburn, skin irritation and a maple syrup smell in sweat and urine.
Research into potential fenugreek side effects is limited, but as a food ingredient, fenugreek generally is considered safe to use. Even when used as a supplement, side effects are rare at the recommended dosage. Fenugreek side effects most often occur when a dose of more than 100 grams is taken daily.
Iron absorption might be hampered by fenugreek. For this reason, the supplement is not recommended for people with anemia. The supplement also might interfere with thyroid hormone levels and is not recommended for those who are undergoing treatment for a thyroid condition.
At high doses, fenugreek can cause internal bleeding. Symptoms such as black tarry stools, bright red blood in the stool, blood in vomit, weakness or numbness in a limb, blurred vision, difficulty speaking or severe headaches might be signs of internal bleeding. Anyone experiencing any of these symptoms should discontinue the use of the supplement and seek immediate medical attention.
Women who are pregnant or breastfeeding should avoid fenugreek supplements as well. Although the fenugreek side effects relating to the unborn and newborn children require further study, fenugreek can stimulate uterine contractions and could trigger early labor or a miscarriage. It generally is recommended that women who are pregnant or breastfeeding consult a doctor before taking any dietary supplement.
Allergic reactions are possible with any supplement, and some people might react to fenugreek. Symptoms such as a rash, hives or itching might indicate an allergy. Swelling is a potentially dangerous symptom, especially if the throat swells and the airway is obstructed. If these symptoms are observed, immediate medical attention is required.
As a dietary supplement and herbal remedy, fenugreek has been used to treat conditions such as indigestion, fever, respiratory and kidney disorders, arthritis, high cholesterol, diabetes and minor skin conditions and injuries. Fenugreek also has been used to increase milk production for breastfeeding mothers. Some studies into the effects of fenugreek have been promising, but dietary supplements do not undergo the testing that is required for medicines, and fenugreek has not been proved to be effective for any medical application.