Effects of Pre-Existing Diseases on Your Health Insurance An illness or condition is considered to be pre-existing if a doctor diagnosed it at least 48 months before the date the health insurance policy was issued. Pre-existing conditions, which typically refer to chronic illnesses like diabetes, hypertension, heart disorders, etc, will not be covered under this category. This includes general fever and colds. Following a medical evaluation and a brief waiting period, the insurance company will approve the insurance request. Interested in learning more? Click here to read more here.