Reported side effects from cordyceps supplements include nausea, diarrhea, dry mouth and mild stomach upset. A lack of human studies examining this herb means that other side effects not yet discovered are possible. Anytime you start a new supplement, watch for any unusual changes or symptoms. Besides being used for medicinal purposes, the Chinese have long consumed cordyceps as a food, which suggests it is generally a substance to consume, and it does not appear to pose any risks for toxicity.
Cordyceps does not have any documented contraindications – instances where you should not use it, such as the presence of a certain medical condition or the use of certain medications. A lack of research, however, means that undiscovered contraindications might exist. If you are pregnant or nursing, avoid it to be on the safe side. If you have any sort of medical condition, particularly liver or kidney disease, check with your doctor about any potential risks of using cordyceps.
Its potential to lower blood sugar suggests cordyceps might help manage diabetes. When using supplements that perform similar actions as drugs, you might require dosage reductions in your medications to compensate for the effects. If you take insulin or other diabetes medications, it might be necessary to make dosage adjustments to avoid hypoglycemia, or low blood sugar.
Cordyceps might stimulate testosterone production. If you currently have, or have an increased risk of, a hormone-sensitive disease like prostate cancer, do not use cordyceps without talking to your doctor first.