1. Make sure you’re eligible

You generally need to be enrolled in Original Medicare, Parts A & B (i.e. not in a Medicare Advantage plan) to buy a Medigap.

If you already have a Medicare Advantage plan, you typically can’t use Medigap alongside it. Also, some states have special rules for people under 65 who qualify for Medicare via disability.

2. Know when you can enroll (your “best window”)

The Medigap Open Enrollment Period is your optimal time. It’s a 6-month window that begins the first month you have Medicare Part B and you’re 65 or older. During this period, you have “guaranteed issue” rights: insurers can’t deny you a Medigap policy or charge more because of health issues.

If you miss this window, insurers may subject you to medical underwriting, meaning they can deny coverage or charge higher premiums due to health conditions.

3. Compare plan letters & benefits

Use resources like Medicare’s official site or a Medigap plan finder to compare what each plan letter offers.

Focus on your health situation: how often you visit doctors, likelihood of hospitalization, etc. Also, some plans (like Plan F) are no longer available to new enrollees in many states depending on your Medicare eligibility date.

4. Choose an insurance company

After picking the plan letter (e.g. Plan G), compare premiums among insurers in your area offering that plan.

Premiums vary by insurer, and factors like age, gender, zip code, and smoking status often matter. Also check the insurer’s reputation, financial strength, and customer service.

5. Apply

Many insurers allow you to apply online, by phone, or via paper application.

During your Medigap Open Enrollment Period, you should get guaranteed acceptance (no medical questions). After that, underwriting may apply.

6. Determine effective date & overlap

Your policy typically starts the first of the month after you apply (unless you request a later date).

Be careful to avoid gaps in coverage. Also, check if there’s a waiting period or “preexisting condition exclusion” in your state (though many states limit or prohibit that for new enrollees in the open enrollment window).

7. Add any needed coverage (e.g. Part D, dental, vision)

Since Medigap doesn’t cover drugs, you’ll usually need to enroll in a Part D prescription drug plan (unless you have credible drug coverage already).

Also consider supplemental plans for dental, vision, hearing, or other gaps not covered by Medicare + Medigap.

8. Keep track of when you can switch or cancel

In some states, there are “free look” periods or limited windows when you can change your Medigap plan without underwriting.

If your needs change, check if your state allows plan changes or “birthday rule” switches. Also, when your health changes, comparing alternatives might make sense.