The Medigap Premium Has a Pricing Method: Read It Before You Budget the Monthly Line
The Medigap premium is set by a pricing method, a carrier's rate history, and the plan letter you choose, so read those three before you put the monthly line on the runway.
A Medicare Supplement, or Medigap, policy helps pay some of the costs that Original Medicare leaves with you, such as certain coinsurance and deductibles. It does not pay for custodial help at home, and it does not replace a long-term care plan (Medicare.gov). That makes its premium a fixed monthly line on the runway, and the premium is the part of the cost you can compare most directly.
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Find the pricing method first
Medigap premiums are set by the insurer under rules that vary by state, and three pricing methods come up most often. Community-rated premiums are not based on age, so people of the same plan pay the same rate in a given area. Issue-age-rated premiums are set by the age at purchase and then move only with the carrier's general rate changes. Attained-age-rated premiums rise as the insured gets older. Ask the carrier which method applies to the plan you are considering, and get the answer in writing. Some carriers also price by tobacco use, so ask that as well.
Compare the same letter across carriers
Medigap plans are sold under standard letters, and the benefits behind each letter are the same from one carrier to the next (Medicare.gov). The price is not the same. When you compare, hold the letter fixed and vary the carrier, the pricing method, and the rate change history. Do not compare two different letters just because one is cheaper, since you would be comparing coverage and price at once.
Budget the next rate change, not only today's
Ask the carrier for its history of rate changes on that plan and the notice it gives before an increase. Put the current premium on the runway, then add a separate line for the next rate change, sized from the carrier's own history. If the carrier cannot or will not give a history, ask Missouri SHIP to review the policy with you before you commit.
Keep the Part B line separate
The Medigap premium is not the Part B premium. The Part B premium can be adjusted for income under rules SSA administers (SSA), so it is a second monthly line with its own source. Check the Medicare notice you receive before you add the two together, and enter each one on its own row.
Where to get the comparison checked
Missouri SHIP counseling is free and can walk through a pricing method and a rate change notice (Missouri SHIP). Aging Ahead can connect you to local counseling for the household (Aging Ahead). The Sources page lists the references behind these lines.
Where this stops
Which coverage is medically needed is for the physician to decide. Whether an insurer must accept an application, and what the policy contract says in a dispute, is for the insurer's paper to answer and, if it comes to a fight, for a lawyer.