Don't take cordyceps if you have cancer, diabetes, or a bleeding disorder. Women who are pregnant or breastfeeding and children should avoid cordyceps. We don’t know if cordyceps is safe for them. Cordyceps is generally safe, but it may cause upset stomach, nausea, and dry mouth in some people. Tell your doctor about any supplements you’re taking, even if they’re natural. That way, your doctor can check on any potential side effects or interactions with medications.