The Open Enrollment period is the six-month period beginning on the first day of the month in which you are enrolled in Medicare Part B. If you are on Medicare under age 65, you will also have a six-month Open Enrollment period when you reach age 65. This period lasts 6 months. When did your period begin? Look at your Medicare card to see when Medicare did/will start. During the open enrollment is the best time to purchase a medicare supplement. Often people get confused regarding the terms medicare supplement and medigap. Medicare supplement and medigap refer to exactly the same type of insurance policy and are therefore synonymous. This is the best time to purchase a medicare supplement because an insurance company cannot turn you down, apply any conditions, or charge more due to a health problem. A pre-existing condition is a condition for which medical advice was given or treatment was received from a physician within 6 months before the effective date of coverage. If you are 65 years of age or older, insurance companies can apply a waiting period of up to six-months for pre-existing conditions to your medigap policy, but that can be eliminated or shorten if you have had prior creditable coverage. Most seniors start Medicare Part B when they turn 65, so for most seniors this is the best time to purchase a Medicare Supplement.