Medicare supplemental insurance, also known as Medigap, is additional insurance that helps cover the costs that Original Medicare doesn't pay for, such as copayments, coinsurance, and deductibles. The best time to buy Medicare supplemental insurance is during your Medigap Open Enrollment Period. This period starts on the first day of the month in which you are both 65 years old or older and enrolled in Medicare Part B, and it lasts for six months. During this time, you have guaranteed issue rights, which means that insurance companies cannot deny you coverage or charge you higher premiums based on your health status. If you miss your Medigap Open Enrollment Period, you may still be able to buy a Medicare supplemental insurance policy, but the insurance company can use medical underwriting to determine your eligibility and may charge you higher premiums. It's important to note that Medicare supplemental insurance is different from Medicare Advantage plans, which are an alternative way to receive your Medicare benefits. If you have a Medicare Advantage plan, you cannot also have a Medicare supplemental insurance policy. To purchase Medicare supplemental insurance, you can contact insurance companies that offer Medigap policies in your state. They can provide you with information about the available plans, coverage options, and costs. It's a good idea to compare different plans and prices to find the one that best meets your needs and budget. Remember to review the terms and conditions of the policy carefully before making a decision. I hope this information helps! Let me know if you have any other questions.