Medigap Rules in Colorado: Enrollment and Switching

In Colorado, your strongest right to buy a Medicare Supplement is your six-month Medigap Open Enrollment Period, which starts the first month you are 65 or older and enrolled in Part B. During it, no company can turn you down or charge more because of your health. After it, you need a guaranteed issue right, or the company can use health questions. Colorado has no birthday rule for switching policies. Colorado does require companies to sell Medigap to people under 65 who have Medicare because of a disability, and it adds a guaranteed issue right for people who lose Medicaid. This guide sets out each rule with its source.

Colorado Medigap rules at a glance

Your six-month Medigap Open Enrollment Period

The window starts automatically the first month you are both 65 and enrolled in Part B, and lasts six months. You can buy any Medigap plan sold in Colorado at the same price a healthy person pays. It happens once. If you delay Part B because you are still covered by an employer plan from current work, the window waits for you and starts when your Part B does.

A company can still apply a waiting period of up to six months for a pre-existing condition treated or diagnosed in the six months before coverage starts. If you had creditable coverage, such as an employer group plan, without a break of more than 63 days, that waiting period is shortened or removed.

Guaranteed issue rights after your window

According to the Colorado Division of Insurance, you can still buy a Medigap policy without health questions if:

• Your Medicare Advantage plan leaves Medicare, stops serving your area, or you move out of its service area.
• You have Original Medicare and an employer group plan (including retiree, COBRA or union coverage that pays after Medicare) and that coverage is ending.
• You have a Medicare SELECT policy and move out of its service area.
• Trial right: you joined a Medicare Advantage plan or PACE when first eligible for Part A at 65, and leave within the first year.
• Trial right: you dropped a Medigap policy to join a Medicare Advantage plan or SELECT policy for the first time, have been in it less than a year, and want to switch back.
• Your Medigap company goes bankrupt or your coverage ends through no fault of your own.
• You leave a Medicare Advantage plan or drop a Medigap policy because the company broke the rules or misled you.
• Colorado only: you had Medicaid when you first became eligible for Medicare, so did not need a Medigap policy, and later lose Medicaid eligibility.

Switching Medigap policies in Colorado

Colorado has no birthday rule. The NAIC state chart (as of May 11, 2026) does not list one for Colorado, and the Division of Insurance guide says that in most cases there is no guarantee you can buy a new Medigap policy, because the company can decide based on your health.

You can still apply. If you pass the health questions and have had your current policy at least six months, the new policy generally must cover pre-existing conditions with no waiting period. You get a 30-day free look on the new policy, paying both premiums for that month, so you can be sure before canceling the old one.

• Never cancel your current policy until the new company approves you in writing.
• If you are leaving Medicare Advantage for a supplement, get the Medigap approval first, then disenroll from the Advantage plan in writing or through 1-800-MEDICARE. Stopping premium payments does not disenroll you.
• Compare the new policy's pricing method (attained age, issue age or community rated), not just this year's premium.

Under 65 with Medicare in Colorado

Federal rules do not guarantee Medigap to people under 65, but Colorado does for people on Medicare because of a disability. The Division of Insurance publishes separate premium charts for disabled beneficiaries under 65, and rates may be higher than at 65. When you turn 65 you get guaranteed issue rights again, so compare policies then: you may be able to move to a lower price.

If you have End-Stage Renal Disease, ask the company how its under-65 rules apply to you before you apply, and compare Medicare Advantage options as well.

What under-65 coverage costs

The Division of Insurance 2026 to 2027 premium charts include a separate page for disabled beneficiaries under 65 (non-smoker, Denver ZIP 80202). Plan G runs from $191 to $581 a month for women and $220 to $655 for men, against $128 to $351 and $147 to $393 at 65. High deductible Plan G is the lower-cost route under 65, at $69 to $129 a month for women and $79 to $143 for men, with a $2,950 deductible in 2026 and $3,050 in 2027 (CMS). Plan A, the most basic plan, runs from $183 to $679 for women.

Under 65, it is worth pricing a Medicare Advantage plan or, if you qualify for Health First Colorado, a dual-eligible Special Needs Plan alongside a supplement. Then mark the month you turn 65 on the calendar: that is when the lower age 65 rates and a new guaranteed issue window arrive.

Pre-existing condition waiting periods, company by company

When you buy outside a guaranteed issue situation, a company can make you wait for coverage of a pre-existing condition. The Colorado premium charts show each company's waiting period in its Notes column, for example Pre-Ex (3) for three months or Pre-Ex (6) for six months. Prior creditable coverage, such as an employer plan, shortens or removes the wait if you had no break of more than 63 days. Read that column before you apply.

Worked scenarios with dates

These are hypothetical people, not clients, to show how the Colorado rules apply.

What I check before you apply

• Which window or right you are in today, with the start and end dates written down.
• Whether you need a letter from a former plan or employer to prove a guaranteed issue right.
• The pricing method, policy fee and pre-existing waiting period for each company, from the state chart and the company itself.
• That the new policy is approved in writing before anything is canceled, and how to cancel the old one without paying an extra month.

Who may not need a Medigap policy

The Division of Insurance points out that some people with Medicare do not need a supplement:

• People eligible for Health First Colorado (Medicaid) or the QMB program.
• People covered by their own or a spouse's employer or retiree plan that works with Medicare.
• People enrolled in a Medicare Advantage plan.
• Some people who get care through the VA or have TRICARE For Life.

Where to check Colorado prices and file a complaint

The Colorado Division of Insurance posts Medigap premium charts by company every year, by plan letter and age, and Medicare.gov publishes the standard chart of what each plan letter covers. If you have a problem with a Medigap policy, the Division of Insurance takes written complaints; its guide lists 303-894-7490.

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The bottom line

In Colorado, buy your Medicare Supplement during your six-month window if you think you will want one, because after that the company can use health questions and there is no birthday rule to fall back on. Know your guaranteed issue rights, including the Colorado right after losing Medicaid, and never cancel a policy before the new one is approved. We are happy to check which window or right applies to you.