Unfortunately, Medigap premium increases typically happen every year. They usually go up on your birthday month or your policy anniversary.
The average Medigap rate increases are between 5% and 8% each year, depending on the plan and state, but they could be more or less. As mentioned earlier, Medicare Supplement premiums generally increase based on the age of the Medicare beneficiary due to the rating method their insurance company uses.
Monthly premiums also typically increase annually because of inflation. Furthermore, since Medicare usually increases medical costs and Medigap plans generally cover these costs, insurance companies have to increase premiums to keep covering them.