Stomach irritation and/or nausea is a common side effect, especially with higher potency products. Other possible side effects include a general stimulatory effect that may manifest as anxiety, irritability, and/or insomnia. Since no safety data exist for use during pregnancy or breast-feeding, adrenal extract should not be used in these situations unless supervised by a doctor.

Consumption of excessive amounts may produce signs and symptoms of corticosteroid excess similar to those experienced with the drug prednisone. However, serious side effects are not likely to result from taking a large amount of an adrenal extract for a short period of time or from excessive intake on a single occasion, but rather from long-term use of high amounts. With prednisone (a synthetic cortisone-like drug) at lower doses (less than 10 mg per day), the most notable side effects are usually increased appetite, weight gain, retention of salt and water, and increased susceptibility to infection.