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Medicare in Colorado

Since 2003, Colorado has required Medigap insurers to make their plans available to disabled beneficiaries under age 65

Key takeaways

  • More than 1 million Colorado residents are enrolled in Medicare.1
  • About 51% of Medicare beneficiaries in Colorado have Medicare Advantage plans.1
  • There are Medicare Advantage plans available in most Colorado counties for 2023 (but not in eight rural counties in eastern Colorado), with plan options ranging from just a few to more than 35, depending on the county.2
  • 37 insurers offer Medigap plans in Colorado.3 Since 2003, state law has required Medigap insurers to offer plans to disabled Medicare beneficiaries under age 65, but premiums are higher for that population.
  • 78% of Colorado Medicare beneficiaries have Part D prescription drug coverage, either as a stand-alone plan or as part of a Medicare Advantage plan.1

Nationwide, more than 65 million people are enrolled in Medicare.4 As of May 2023, there were 1,001,428 residents with Medicare in Colorado.1 That’s about 17% of the state’s total population, compared with more than 19% of the United States population enrolled in Medicare.54
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More than 91% of people with Medicare in Colorado are eligible due to their age (ie, being at least 65), while about 8% are eligible due to a disability, including a diagnosis of amyotrophic lateral sclerosis (ALS) or kidney failure.1 Nationwide, about 88% of Medicare beneficiaries are eligible due to age, and almost 12% are eligible due to disability.4

Medicare Advantage in Colorado

Nationwide, about 35% of all Medicare beneficiaries had Medicare Advantage plans as of 2018.6 In Colorado, Medicare Advantage was a little more popular, with nearly 38% of the state’s Medicare beneficiaries enrolled in Medicare Advantage plans.7 And by May 2023, in keeping with a nationwide trend of increasing Medicare Advantage enrollment, 51% of Colorado Medicare beneficiaries were enrolled in Medicare plans (this includes some Medicare cost plans in Colorado, but the vast majority of the plan enrollees were in Medicare Advantage plans).1 The other 49% of Colorado’s Medicare beneficiaries had opted instead for coverage under Original Medicare.

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Medicare Advantage plans are provided by private insurers, which each have their own service area, so plan availability varies by area. There are Medicare Advantage plans available in most parts of Colorado in 2023, but there are eight rural counties along the eastern edge of the state where no Medicare Advantage plans are available. In the rest of the state, Medicare Advantage plan availability in 2023 ranges from just two or three plans in some counties, to more than 35 in others.2

Medicare Advantage enrollment is available when a person is first eligible for Medicare, and there are also annual enrollment windows when beneficiaries can switch to Medicare Advantage or pick a different Medicare Advantage plan. Medicare beneficiaries can switch from Original Medicare to Medicare Advantage plans, and vice versa, during the Medicare Annual Election Period (AEP) each fall (October 15 through December 7), with coverage effective January 1. And there is also a Medicare Advantage open enrollment period (January 1 to March 31) during which people who are already enrolled in Medicare Advantage plans can switch to a different Medicare Advantage plan or drop their Medicare Advantage plan and enroll in Original Medicare instead.

Medigap in Colorado

Because Original Medicare has out-of-pocket healthcare costs that can be substantial (and there is no cap on how high out-of-pocket costs can be with Original Medicare), many enrollees use Medigap policies to supplement Original Medicare, covering some or all of the out-of-pocket costs (such as coinsurance and deductibles) that people would otherwise incur if they only had Original Medicare on its own. Employer-sponsored plans and Medicaid serve as supplemental coverage for about 48% of all Medicare beneficiaries nationwide,8 but Medigap policies fill a coverage need for people who don’t have access to Medicaid or an employer-sponsored plan, and who prefer Original Medicare over Medicare Advantage plans.

As of 2023, there are 37 insurers in Colorado offering Medigap policies.3 And as of 2020, there were 232,748  Medicare beneficiaries in Colorado who had Medigap coverage, according to an analysis from America’s Health Insurance Plans (AHIP).9 That was more than a third of Colorado’s Original Medicare population in 2020 (Medigap plans cannot be used with Medicare Advantage coverage).10 In many states, Medigap enrollment has been declining as Medicare Advantage growth outpaces overall Medicare enrollment growth (Medigap policies cannot be used with Medicare Advantage plans).  

Medigap policies are standardized under federal rules, so Medicare Supplement Plan A offers the same healthcare benefits regardless of which insurer offers it, as does Medicare Supplement Plan G, Plan N, etc. (premiums vary significantly from one insurer to another — initially and in terms of how they increase over time — as do things like customer service and additional benefits beyond the standardized benefits, such as a 24-hour nurse hotline).11 But Medigap standardization means that policy comparisons are easier than they are for other types of health insurance.

Medigap policies can be priced using attained-age rating, issue-age rating, or community rating. Colorado does not require insurers to use a particular approach, so most Medigap insurers in Colorado use attained-age rating, which means that a person’s premiums increase as they get older. There are a handful of insurers in the state that use issue-age rating, which means the rates are based on the age the person was when they enrolled.12

Under federal rules, people are granted a six-month window during which they can enroll in a Medigap policy regardless of their medical history. This window starts when they’re at least 65 and enrolled in Medicare Part B. Federal rules do not, however, guarantee access to a Medigap policy if you’re under 65 and eligible for Medicare as a result of a disability.13

To address this, the majority of the states have implemented rules ensuring at least some access to Medigap policies for people who are under age 65, and there has been slow but steady progress on this. Today, there are at least 33, including Colorado.13

Colorado statute (see 3 CCR 702-4 Series 4-3 Section 10) was changed in 2003 to ensure access to Medigap for people under age 65. Colorado requires Medigap insurers to offer all of their plans to people under age 65, with the same six-month enrollment window that applies to people who are aging onto Medicare. So a person under age 65 who becomes eligible for Medicare in Colorado has six months, starting when they’re enrolled in Medicare Part B, to sign up for a guaranteed-issue Medigap plan. When Colorado implemented this rule in 2003, there was a one-time six-month open enrollment window (September 2003 through February 2004) during which people under age 65 who were already enrolled in Medicare could sign up for a Medigap policy.

Although Medigap plans are guaranteed-issue for people under 65 during their six-month enrollment window, insurers can charge higher premiums for people under 65. As of 2022/23, virtually all of the insurers offering Medigap plans in Colorado were charging less than $200/month (some less than $110/month) for Medigap Plan A if the enrollee was 65-years-old. But for a person under the age of 65, premiums for Plan A varied from about $150 to more than $800 per month. The state does regulate the extent to which premiums can be higher for people under 65, with extensive rules governing what an insurer can charge as a “credibility-weighted average age premium rate” (see Section 10(E) of the statute).

Disabled Medicare beneficiaries have access to the normal Medigap open enrollment period when they turn 65. At that point, they have access to any of the available Medigap plans, at the standard age-65 rates.

Disabled Medicare beneficiaries have the option to enroll in a Medicare Advantage plan instead of Original Medicare. Medicare Advantage plan monthly premiums are not higher for those under 65. But Medicare Advantage plans have more limited provider networks than Original Medicare, and total out-of-pocket costs can be as high as $8,300 per year for in-network care (as of 2023), plus the out-of-pocket cost of prescription drugs.14

Special enrollment period in 2021 for Medigap enrollees with Plans F or C

Colorado’s Division of Insurance finalized an important special enrollment period to make it easier for enrollees with Medigap Plans F and C to switch to Plans G and D. Here’s the backstory on this, and why this special enrollment period, which ran for the first six months of 2021, was beneficial for Colorado’s Medicare population:

After the end of 2019, newly-eligible Medicare beneficiaries cannot enroll in Medigap Plans F or C. These have long been among the most popular Medigap plans, but legislation (MACRA) enacted in 2015 requires them to no longer be sold to newly-eligible enrollees, because lawmakers wanted to phase out Medigap plans that cover the Part B deductible (Plans C and F are the only Medigap policies that cover the Part B deductible).

The idea is to try to curb overutilization of health care by ensuring that Medicare beneficiaries have to spend at least some of their own money in out-of-pocket charges when they seek medical treatment (the Part B deductible is $233 in 2022, so it’s a fairly small cost when compared with average total medical expenses).

Medicare beneficiaries who already had Plans F or C prior to 2020 are able to keep them, but there is some concern that premiums might start to increase faster than usual for these plans since they are no longer allowed to enroll newly-eligible beneficiaries. Health care costs tend to rise considerably with age, but each year’s incoming group of 65-year-olds helps to keep Medigap premiums much more stable than they would be without newly-eligible enrollees. So it’s possible that premium increases for Plans C and F could start to outpace premium increases for other Medigap plans, although we won’t know for sure until several years have passed under the new rules.

Healthy enrollees have the option to apply for a different Medigap plan at any time, but Medigap enrollees with pre-existing conditions may find it difficult or impossible to switch plans. Applications submitted after an enrollee’s initial enrollment window has passed are subject to medical underwriting (unless they’re eligible for very limited special enrollment periods), and there is no annual open enrollment period for Medigap, the way there is for Medicare Part D plans and Medicare Advantage plans.

So Colorado regulators created a one-time special enrollment period (January to June 2021) that allowed any Medicare beneficiary enrolled in Plan C or Plan F to switch to Plan D or Plan G, without medical underwriting.

Medicare Part D in Colorado

Original Medicare does not cover outpatient prescription drugs.

Many Medicare beneficiaries have prescription drug coverage from an employer or Medicaid, but for those who don’t, Medicare Part D prescription drug plans are an important part of having insurance coverage. Medicare Part D prescription drug coverage was created under the Medicare Modernization Act of 2003, and individuals can be enrolled in a Medicare Part D prescription drug plan on a stand-alone basis or as part of a Medicare Advantage plan with integrated Medicare Part D prescription drug coverage.

As of May 2023, there were 298,581 Colorado Medicare beneficiaries enrolled in stand-alone Medicare Part D prescription drug plans, and another 486,580 beneficiaries had Medicare Part D prescription drug coverage integrated with their Medicare Advantage plans. In total, 781,161 Colorado Medicare beneficiaries had Part D prescription drug coverage, accounting for more than three-quarters of the state’s Medicare population.1

For 2023 coverage, there are 23 stand-alone Medicare Part D prescription drug plans available in Colorado, with premiums starting at $3.50.15

Medicare Part D prescription drug enrollment follows the same schedule as Medicare Advantage plans: Beneficiaries can pick a Medicare Part D prescription drug  plan when they first become eligible for Medicare, and there’s also the Annual Election Period each fall (October 15 to December 7) when Medicare beneficiaries can pick a different Medicare Part D prescription drug plan or enroll for the first time (note that there’s a late enrollment penalty for people who delay their initial enrollment and don’t have other creditable drug coverage in place). Medicare beneficiaries are encouraged to actively compare the various options each fall in order to see which one will best meet their personal prescription needs (plans vary from one year to the next, and a beneficiary’s current prescriptions may differ from what they were a year ago).

How does Medicaid provide financial assistance to Medicare beneficiaries in Colorado?

Many Medicare beneficiaries receive financial assistance through Medicaid with the cost of Medicare premiums, prescription drug expenses, and services not covered by Medicare – such as long-term care.

Our guide to financial assistance for Medicare enrollees in Colorado includes overviews of these benefits, including Medicare Savings Programs, long-term care coverage, and eligibility guidelines for assistance.

Medicare in Colorado: Resources

If you have questions about Medicare eligibility in Colorado or Medicare enrollment in Colorado, you contact the Colorado State Health Insurance Assistance Program (there are offices in each county).

The Colorado Division of Insurance also maintains a useful Senior Publications page that includes a variety of helpful resources and information to address questions you might have about Medicare coverage in Colorado.

The Colorado Division of Insurance also regulates Medigap plans in the state, although those plans must also conform to the federal government’s standardization rules, as described above (the governance of Medicare Advantage and Medicare Part D prescription drug plans mostly lies with the federal government, the state is only responsible for licensing the insurers that offer these plans and ensuring they remain financially solvent).

This page is a comprehensive resource that details how Colorado Medicaid can provide financial assistance to Medicare beneficiaries in the state who have limited income and assets.

Louise Norris is an individual health insurance broker who has been writing about health insurance and health reform since 2006. She has written dozens of opinions and educational pieces about the Affordable Care Act for Her state health exchange updates are regularly cited by media who cover health reform and by other health insurance experts.


  1. Medicare Monthly Enrollment – Colorado ” Centers for Medicare & Medicaid Services Data, May 2023.       
  2. Jeannie Fuglesten-Biniek and Meredith Freed. “Medicare Advantage 2023 Spotlight: First Look.” Kaiser Family Foundation, November 10, 2022.  
  3. Supplement Insurance (Medigap) Plans in Colorado.” Accessed September 13, 2023.  
  4. Medicare Monthly Enrollment – U.S.” Centers for Medicare & Medicaid Services Data, May 2023.   
  5. U.S. Census Bureau Quick Facts: U.S. & Colorado.” U.S. Census Bureau, July 1, 2022. 
  6. Monthly Medicare Enrollment – US (2018).” Centers for Medicare & Medicaid Services Data, May 2018. 
  7. Medicare Monthly Enrollment – Colorado (2018).” Centers for Medicare & Medicaid Services Data, May 2018. 
  8. Ochieng, Nancy, Gabrielle Clerveau, and Tricia Neuman. “A Snapshot of Sources of Coverage among Medicare Beneficiaries.” Kaiser Family Foundation, August 14, 2023. 
  9. The State of Medicare Supplement Coverage.” AHIP, Page 10. February 2023. 
  10. Medicare Monthly Enrollment – Colorado (2020) ” Centers for Medicare & Medicaid Services Data, May 2023. 
  11. 2023 Choosing a Medigap Policy.” Page 11. Accessed September 19, 2023. 
  12. Medicare Supplement Insurance Policies in Colorado.” Page 7. Colorado Department of Regulatory Agencies. Accessed October 23, 2023. 
  13. 2023 Choosing a Medigap Policy.” Page 40. Accessed September 19, 2023.  
  14. Fuglesten Biniek, Jeannie, Nancy Ochieng, Meredith Freed, Anthony Damico, and Tricia Neuman. “Medicare Advantage in 2023: Premiums, out-of-Pocket Limits, Cost Sharing, Supplemental Benefits, Prior Authorization, and Star Ratings.” KFF, August 9, 2023. 
  15. Fact Sheet – Centers for Medicare & Medicaid Services. Page 17. CMS, September 29, 2022 

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