Possible side effects associated with Instaflex include nausea, heartburn and diarrhea, according to ConsumerProductWatch.org. Adverse side effects may occur in those who are allergic to any of Instaflex's active ingredients.
Consumer Health Digest warns that a person could also experience unpleasant side effects if she is pregnant or has heart disease. Although Instaflex contains natural ingredients that typically do not interact with other medications, it is still important for a patient to consult a doctor prior to using Instaflex if she is taking other prescription or over-the-counter drugs, so as to avoid any adverse side effects. Those with a known allergy to shellfish should not take Instaflex.