Colorado Medigap Rules: Open Enrollment, Under 65 and Medicaid Loss

Colorado requires Medigap insurers to sell to applicants under 65 who are new to Medicare Part B, which federal law generally doesn't require. Under Colorado Division of Insurance Regulation 4-3-1 (3 CCR 702-4), a Medigap insurer may not deny any policy available for sale in Colorado, or price it on health, for an applicant under 65 who applies before or during the six months beginning with the first month of Medicare Part B enrollment. Colorado's rule gives the same protection for six months starting the first month an applicant is both 65 or older and enrolled in Part B, and it sets guaranteed-issue windows that run as long as six months after some involuntary coverage losses.1,2,3

In This Guide

• Your One-Time Colorado Medigap Open Enrollment Window
• Will Colorado Medigap Cover Your Pre-Existing Conditions?
• Can You Buy Medigap in Colorado Before 65?
• When Can You Buy Colorado Medigap After Losing Other Coverage?
• Which Medigap Plans You Can Buy in Colorado
• Keeping or Switching a Colorado Medigap Policy
• Should You Choose Medigap or Medicare Advantage in Colorado?
• Which Colorado Medigap Window Applies to You?
• Where to Get Medigap Help in Colorado
• Frequently Asked Questions
• Learn More

Your One-Time Colorado Medigap Open Enrollment Window

Section 10.A of Colorado's Regulation 4-3-1 sets the Colorado Medigap open enrollment period: the six months beginning with the first day of the first month in which a person is both 65 or older and enrolled in Medicare Part B. During that window, no issuer may deny or condition the issuance or effectiveness of any Medicare supplement policy available for sale in Colorado, or discriminate in its price, because of the applicant's health status, claims experience, receipt of health care or medical condition. Section 10.A also requires each issuer to make every policy it currently has available to all qualifying applicants, regardless of age.3

The Colorado Division of Insurance's September 2025 Medigap guide calls the first six months after enrolling in Medicare Part B "the best time to buy a Medigap policy."3

Colorado's window sits on top of a federal floor. Section 1882 of the Social Security Act, at §1882(s)(2)(A), sets the same six-month protection nationally, starting with the first month a person is 65 or older and enrolled in Part B. Medicare.gov describes the federal Medigap Open Enrollment Period as a one-time period that doesn't repeat every year. Outside the federal Medigap Open Enrollment Period, Medicare.gov says, an insurance company is allowed to deny a Medigap policy to someone who doesn't meet its medical underwriting requirements, and the policy may cost more.2

Will Colorado Medigap Cover Your Pre-Existing Conditions?

Getting a Colorado Medigap policy during open enrollment doesn't automatically mean every condition is covered from day one. Section 10.C of Colorado's Regulation 4-3-1 ties the answer to creditable coverage, meaning the continuous health coverage the applicant had before applying:

• Six months or more of continuous creditable coverage: the issuer may not exclude benefits based on a preexisting condition for an applicant who applies during the open enrollment window and, as of the application date, has had at least six months of continuous creditable coverage.
• Less than six months: the issuer must shorten any preexisting-condition exclusion period by the total time the applicant has had creditable coverage.3

Outside those Section 10.C protections and the replacement rules in Section 22, Section 10.K of Colorado's Medigap rule lets a policy exclude benefits during its first six months for a preexisting condition that was treated or diagnosed in the six months before coverage began.3

Section 8.1.A of Colorado's Regulation 4-3-1 caps how far any Medigap preexisting-condition limit can reach. A policy with coverage effective on or after June 1, 2010 may not exclude or limit benefits for losses incurred more than six months after coverage begins because of a preexisting condition. Section 8.1.A also bars a Medigap policy from defining a preexisting condition more broadly than a condition for which a physician gave medical advice, or recommended or provided treatment, within the six months before coverage began.3

Can You Buy Medigap in Colorado Before 65?

Federal law generally doesn't require insurance companies to sell Medigap policies to people under 65, according to Medicare.gov.2 Colorado's Medigap rule goes further: Section 10.B of Colorado's Regulation 4-3-1 bars an issuer from denying, conditioning or health-pricing any Medicare supplement policy available for sale in Colorado for an applicant under age 65 who applies before or during the six months beginning with the first day of the first month the applicant is enrolled in Medicare Part B.1

Three more provisions of Colorado's Medigap rule shape the under-65 window:

• Every available policy. Under Section 10.D, each Medicare supplement policy an issuer currently has available must be made available to every applicant the issuer is required to cover.
• Active marketing. Under Section 10.F, each issuer must actively market Medicare supplement insurance during the under-65 open enrollment periods.
• No steering. Under Section 10.G, an issuer may not encourage a person enrolled in Part B by reason of disability to skip applying, or to seek coverage from another issuer, because of the person's health.1

The Colorado Division of Insurance's Medigap guide states that "in Colorado, companies are also required to sell to under-65 disabled beneficiaries." The same guide warns that rates may be higher for disabled Medicare beneficiaries under 65 than at 65, and that at 65, disabled Medicare beneficiaries once again have guaranteed issue rights and should review available policies for a better price. The Centers for Medicare & Medicaid Services (CMS) guide Choosing a Medigap Policy lists Colorado among the states that, at the time of printing, required insurance companies to offer at least one kind of Medigap policy to people with Medicare under 65.1

A Coloradan under 65 who buys Medigap and later turns 65 reaches a second protected window, because Section 10.A's open enrollment window opens in the first month the person is both 65 or older and enrolled in Part B.3,1

When Can You Buy Colorado Medigap After Losing Other Coverage?

Section 11 of Colorado's Regulation 4-3-1 protects Coloradans who lose other coverage after their open enrollment window has passed. For an eligible person who applies inside the guaranteed-issue period, an issuer may not deny or condition a covered policy it offers to new enrollees, may not price the policy on health status, claims experience, receipt of health care or medical condition, and may not impose a preexisting-condition exclusion.3

Colorado's Regulation 4-3-1 lists the situations that create the right, and each situation carries its own window:

• An employer plan ends. A Colorado guaranteed-issue right applies when an employee welfare benefit plan that supplements Medicare terminates or stops providing all supplemental benefits, or when an employer plan that is primary to Medicare ends or stops providing all health benefits because the person leaves the plan. Under Section 11.C.1, if the cancellation was not for nonpayment of premium or fraud, the window begins on the later of the termination notice (or a claim-denial notice) or the date coverage ends, and runs six months after that for an involuntary exit or 63 days for a voluntary one.
• A Medicare Advantage plan ends, or you move. The right also applies when a Medicare Advantage plan's certification is terminated, when the plan is discontinued in the area where the person lives, or when the person can no longer stay in the plan because of a change of residence.
• A first-year exit from Medicare Advantage or PACE. The right also applies to a person who, upon first becoming eligible for Medicare Part A, enrolled in a Medicare Advantage plan or with a PACE provider and disenrolls within 12 months after that enrollment took effect.
• A dual enrollee loses Medicaid. Under Section 11.B.8, the right also applies to a person enrolled in both Medicare and Medicaid who loses eligibility for Medicaid health benefits.3

For the Medicare Advantage and first-year Medicare Advantage or PACE situations, Colorado's Regulation 4-3-1 sets two windows. Under Section 11.C.2, when the enrollment is terminated involuntarily, the guaranteed-issue window runs from the termination notice until six months after coverage ends. Under Section 11.C.4, when the person disenrolls voluntarily, the window opens 60 days before the disenrollment effective date and closes 63 days after it.3

Colorado's Medicaid-loss right falls under the Section 11.C.6 catch-all window, which covers any eligible person not described in the rule's preceding time-period provisions. The catch-all runs from the effective date of a voluntary disenrollment to 63 days later, or, for an involuntary termination not due to nonpayment of premium or fraud, from the termination date to six months later. The Colorado Division of Insurance's Medigap guide describes the Medicaid right in its own words: a person has a guarantee issue right after having Medicaid coverage when first eligible for Medicare and later losing eligibility.3

Which plans a Colorado guaranteed-issue right reaches

Colorado's Regulation 4-3-1 attaches different plan choices to different situations, so a single list does not describe every guaranteed-issue right:

• Employer plan ending and Medicare Advantage plan ending (Sections 11.B.1 through 11.B.4): under Section 11.E.2, a person first eligible for Medicare before January 1, 2020 may buy Plan A, B, C, F (including high-deductible F), K or L from any issuer, and a person first eligible on or after January 1, 2020 may buy Plan A, B, D, G (including high-deductible G), K or L from any issuer.
• First-year exit from Medicare Advantage or PACE (Section 11.B.6): under Section 11.E.4, the person may buy any Medicare supplement policy offered by any issuer.3

For Colorado's Medicaid-loss right, ask Colorado SHIP which policies an issuer must offer before applying, since Section 11.E.2's list is written for Sections 11.B.1 through 11.B.4.3,1 Medicare.gov notes that its own answers on switching cover only federal rights, which is why Colorado's rule, not the federal summary, is the text to check.3,4

Which Medigap Plans You Can Buy in Colorado

Medicare's official guide Choosing a Medigap Policy (2026) charts the standardized Medigap plans as Plans A, B, C, D, F, G, K, L, M and N. Every insurance company that sells Medigap policies must offer at least Plan A, according to the same Medicare guide.1

Plans C and F are closed to people new to Medicare. Under Social Security Act §1882(z), a Medigap policy that covers the Part B deductible may not be sold to a newly eligible Medicare beneficiary on or after January 1, 2020. Medicare's guide says people new to Medicare on or after January 1, 2020 have the right to buy Plans D and G instead, which give the same benefits without covering the Part B deductible, while someone eligible for Medicare before 2020 who hasn't yet enrolled may be able to buy Plan C or Plan F. Plans E, H, I and J are no longer sold, though someone who already has one can generally keep it.1

Keeping or Switching a Colorado Medigap Policy

Section 8.1.A of Colorado's Regulation 4-3-1 makes every Colorado Medigap policy guaranteed renewable. An issuer may not cancel or nonrenew a policy solely because of the policyholder's health, or for any reason other than nonpayment of premium or material misrepresentation.3

Changing Medigap policies in Colorado is a different matter. The Colorado Division of Insurance's guide warns that in most cases there is no guarantee a person can buy a new Medigap policy, and that Medigap insurers decide whether to insure a person based on health. Medicare.gov gives the federal version: outside the 6-month Medigap Open Enrollment Period, in most cases you won't be able to switch Medigap policies unless you have a guaranteed issue right, and a switch outside that window may mean paying more and answering medical questions.3,4

When a Colorado insurer does accept a replacement, three protections apply:

• Credit for time served. Under Section 22 of Colorado's Medigap rule, the replacing issuer must waive preexisting-condition, waiting, elimination and probationary periods for similar benefits to the extent those periods had already run under the old policy. If the old policy had been in effect for at least six months, the new policy may not impose any such period for similar benefits.
• A 30-day look. Under Section 16, every policy must carry a notice that the policyholder may return it within 30 days of delivery for a premium refund if not satisfied for any reason.
• Keep the old policy until the new one is approved. The Colorado Division of Insurance's guide tells policyholders not to cancel a current Medigap policy until they know for sure they have been accepted for a new one.3

Medicare.gov adds that a person who drops a Medigap policy might not be able to get it, or any policy, back later.4

Should You Choose Medigap or Medicare Advantage in Colorado?

Medicare's booklet Understanding Medicare Advantage Plans states that Medigap helps pay out-of-pocket costs in Original Medicare, and that Medigap can't be used to pay a Medicare Advantage plan's copayments, coinsurance, deductibles or premiums. The same Medicare booklet states that it's illegal for anyone to sell a Medigap policy to a Medicare Advantage enrollee unless the person is switching back to Original Medicare, and that a seller who tries should be reported to the State Insurance Department.5

Two federal points matter to a Coloradan weighing a move between Medigap and Medicare Advantage:

• Dropping Medigap to join Medicare Advantage. Medicare's booklet says that in most cases, a person who drops a Medigap policy to join a Medicare Advantage plan may not be able to get the same policy back.
• The federal trial right. Medicare's booklet says a person who joins a Medicare Advantage plan for the first time and isn't happy with it has a federal "trial right" to buy a Medigap policy and a separate Medicare drug plan when returning to Original Medicare within 12 months of joining.5

Which Colorado Medigap Window Applies to You?

The table below lines up each Colorado Medigap situation with its window and its protection under Regulation 4-3-1.3,1

Where to Get Medigap Help in Colorado

Colorado SHIP gives free, detailed and personal help with Medigap and other Medicare questions at 1-888-696-7213, and its counselors do not sell or promote any health insurance. CMS's Choosing a Medigap Policy guide recommends calling your State Health Insurance Assistance Program to confirm you qualify for a guaranteed issue right, and calling your State Insurance Department if you are denied Medigap coverage in one of those situations.1

For a problem with a current Medigap policy, the Colorado Division of Insurance's guide says to file a complaint with the Division at 303-894-7490 or insurance@dora.state.co.us, and states that complaints must be in writing. The Division's full guide, Medicare Supplement Insurance Policies in Colorado (September 2025), is published with Colorado SHIP.1

For a general Medicare question, 1-800-MEDICARE (1-800-633-4227; TTY 1-877-486-2048) is the official Medicare line, and Medicare.gov says callers can talk or live chat with a real person 24 hours a day, 7 days a week, except some federal holidays.6

Learn More

Find personalized help choosing a Colorado Medigap policy with Brevy's care navigator at brevy.com.

The information on Brevy.com is for educational purposes only and is not a substitute for professional legal, financial, or medical advice. Rules vary by state and program and change frequently. Always verify with the relevant agency or a qualified professional. Brevy is not a law firm, financial advisor, or healthcare provider.