If you take it in the typical amounts used in food, it’s unlikely to cause serious side effects. However, high medicinal doses can sometimes cause reactions such as diarrhea, upset stomach, gas, and headaches. It can also give your urine an unusual odor. Stop taking fenugreek right away and get medical attention if you have signs of an allergic reaction, such as coughing, wheezing, or swelling in your face or mouth.