Medicare Supplement Insurance (Medigap): The Complete Guide to Colorado

Navigating the transition into Medicare is one of the most critical financial and healthcare decisions you will make. While Original Medicare provides a robust foundation of health coverage for seniors in Colorado, it was never designed to pay for everything. It leaves you responsible for deductibles, copayments, and a 20 percent coinsurance on outpatient services that has no annual out-of-pocket maximum limit. If you experience a catastrophic health event, that unlimited 20 percent liability can easily decimate your retirement savings.

To protect against this financial exposure, millions of seniors turn to Medicare Supplement Insurance, universally known as Medigap.

Medigap is private health insurance designed specifically to work alongside Original Medicare (Part A and Part B). It pays the bills that Medicare leaves behind. By paying a predictable monthly premium to a private insurance carrier, you transfer the financial risk of high healthcare costs away from your own checkbook.

This guide serves as your complete, authoritative resource for understanding how Medigap works in Colorado. We will dissect the standardized plan letters, explain the strict enrollment timelines that dictate whether an insurance company can look at your medical history, and give you the comprehensive knowledge you need to choose the right coverage for your healthcare future.

Understanding the Foundation: The Financial Gaps in Original Medicare

To understand the value of a Medigap policy, you must first fully grasp what happens if you rely on Original Medicare alone.

Original Medicare is administered by the federal government and is divided into two primary parts:

• Part A (Hospital Insurance): Covers inpatient hospital stays, skilled nursing facility care, hospice care, and some home healthcare.
• Part B (Medical Insurance): Covers outpatient care, doctor visits, preventive services, surgeries, chemotherapy, and durable medical equipment.

While these parts cover a vast array of medical services, they utilize a cost-sharing model that leaves the beneficiary with substantial financial responsibilities.

The Gaps in Medicare Part A

If you are admitted to a hospital, Part A does not simply cover the bill. Instead, hospital stays are measured in “benefit periods.”

• When you are admitted to the hospital, you must first pay a significant Part A hospital deductible. This deductible is not an annual figure; it applies per benefit period. If you are hospitalized, discharged, and then hospitalized again more than 60 days later, you must pay that full deductible all over again.
• Once the deductible is met, Part A covers your inpatient costs for the first 60 days of your stay.
• If your hospital stay extends into days 61 through 90, you are responsible for a steep daily coinsurance charge.
• For days 91 and beyond, you tap into your “lifetime reserve days,” which come with an even higher daily coinsurance cost. Once those are exhausted, you pay all hospital costs out of pocket.

The Gaps in Medicare Part B

Part B operates differently but carries an even greater financial risk.

• You must first satisfy an annual Part B deductible. You pay 100 percent of your outpatient medical costs until this amount is reached.
• Once the Part B deductible is met, Medicare generally pays 80 percent of the Medicare-approved amount for most covered services.
• You are responsible for the remaining 20 percent.

The danger of the Part B gap is the absence of an out-of-pocket maximum. If you require a knee replacement, regular specialist visits, or expensive outpatient treatments like infusion chemotherapy or radiation, that 20 percent coinsurance scales infinitely. A $100,000 course of treatment means you owe $20,000 out of pocket.

This open-ended financial liability is precisely why Medigap exists.

What is Medicare Supplement Insurance (Medigap)?

Medicare Supplement Insurance, or Medigap, is a health insurance policy sold by private insurance companies licensed to operate in Colorado, such as UnitedHealthcare, Anthem Blue Cross and Blue Shield, Humana, and Aetna Medicare. Its sole purpose is to “bridge the gap” left by Original Medicare’s cost-sharing requirements.

How Medigap Coordinates with Medicare

Medigap operates strictly as a secondary payer. When you visit a doctor or hospital, you hand the receptionist two cards: your red, white, and blue Medicare card, and your Medigap policy card.

1. Your healthcare provider bills Original Medicare directly.
2. Medicare reviews the claim. If it is a covered medically necessary service, Medicare pays its share (typically 80 percent for outpatient care) directly to the provider.
3. The Medicare claims system automatically forwards the remainder of the bill (the claim crossover) to your Medigap insurance carrier.
4. Your Medigap carrier immediately pays the remainder of the bill according to the specific letter plan you chose.

The result is seamless. For a patient with a comprehensive Medigap policy, complex medical billing becomes practically invisible. There are no claim forms to file, and the provider is paid fully on the back end.

The Golden Rule of Medigap Networks

One of the most powerful features of a Medigap policy is its universal acceptance. Medigap policies do not have their own provider networks. There are no HMO or PPO restrictions.

If a doctor, hospital, or facility accepts Original Medicare, they are legally required to accept your Medigap policy, regardless of which insurance company issued it.

Whether you buy your policy from Cigna, Humana, Anthem Blue Cross and Blue Shield, or a smaller regional carrier in Colorado, your access to doctors remains identical. You can seek care at the Mayo Clinic, MD Anderson, or your local specialist in Denver or Colorado Springs, without ever needing a primary care referral or network authorization.

The Standardized Medigap Plans in Colorado

To make shopping for insurance fair and transparent, the federal government requires all Medigap policies to be standardized. Policies are identified by letters (Plan A through Plan N).

Standardization means that every Medigap Plan G sold in Colorado must offer the exact same basic medical benefits. The federal government sets the coverage rules; the private carriers merely administer the policies. An insurance company cannot modify the medical coverage of a Plan G to make it better or worse than a competitor’s Plan G.

Because the medical benefits are identical, carriers in Colorado compete primarily on three factors:

1. The monthly premium they charge.
2. Their history of annual rate increases.
3. Non-medical extra perks (like discounted gym memberships or vision discounts).

Let’s examine the most critical standardized plans available to Colorado residents today.

Medigap Plan G: The Comprehensive Standard

For anyone newly eligible for Medicare, Plan G offers the most comprehensive medical coverage available by law.

Plan G covers effectively every single gap in Original Medicare except for one specific thing: the annual Medicare Part B deductible.

Under a Plan G policy:

• Your Part A hospital deductible is fully paid.
• Your daily hospital coinsurance is fully paid.
• The 20 percent coinsurance for Part B doctor visits, outpatient surgeries, and medical equipment is fully paid.
• Part B Excess Charges (which occur if a doctor refuses to accept Medicare’s standard reimbursement rate) are fully covered.

Once you pay the relatively small Part B annual deductible out of your own pocket at the beginning of the year, Plan G steps in to pay 100 percent of your covered medical costs for the remainder of the calendar year. You will not see another medical bill for any Medicare-approved service, whether you have a simple checkup or a million-dollar organ transplant.

High-Deductible Plan G (HDG): Colorado carriers also offer a variation known as High-Deductible Plan G. This plan functions exactly like standard Plan G, but you agree to pay a much higher annual deductible before the policy begins paying the 20 percent coinsurance. In exchange for taking on this upfront financial risk, the carrier charges you a significantly lower monthly premium. This is highly attractive to healthy individuals who want catastrophic protection but want to keep fixed monthly expenses low.

Medigap Plan N: The Budget-Friendly Alternative

Plan N is the second most popular Medigap policy for new enrollees. It operates similarly to Plan G but introduces a few small cost-sharing mechanisms in exchange for a noticeably lower monthly premium.

Under Plan N, you are still responsible for the Part B annual deductible. Additionally, you take on three specific out-of-pocket costs:

1. Office Visit Copays: You will pay a copay of up to $20 each time you visit a doctor or specialist.
2. Emergency Room Copays: You will pay a copay of up to $50 if you visit the emergency room and are not subsequently admitted to the hospital as an inpatient.
3. Part B Excess Charges: Plan N does not cover excess charges. If a provider does not accept “Medicare Assignment” (the standard Medicare payout), federal law allows them to charge up to 15 percent more than the approved amount. You would be responsible for paying this 15 percent difference out of pocket.

Note on Excess Charges: While excess charges sound intimidating, they are relatively rare. The vast majority of providers nationwide accept Medicare assignment. However, if you travel frequently or demand access to boutique specialists who refuse standard assignment, Plan G may provide better peace of mind.

The Phase-Out of Plan F and Plan C

If you talk to older friends or relatives about Medicare, they will likely tell you they have Plan F. For decades, Plan F was the most popular policy because it covered absolutely everything, including the Part B deductible.

However, Congress passed the Medicare Access and CHIP Reauthorization Act (MACRA). This legislation dictated that, to discourage the overutilization of the healthcare system, newly eligible beneficiaries should have some “skin in the game” for outpatient care.

As a result, any Medigap plan that pays the Part B deductible (Plans F and C) can no longer be sold to anyone who became eligible for Medicare on or after January 1, 2020.

If you were eligible for Medicare prior to that date, you retain the legal right to purchase Plan F or Plan C in Colorado. However, many brokers advise against it. Because no newly turning-65 individuals can enter the Plan F risk pool, the population in that pool is aging rapidly without young, healthy people balancing out the medical claims. Over time, this historically leads to sharper annual premium increases for Plan F compared to Plan G.

Other Medigap Plans (A, B, K, L, M)

Carriers in Colorado do offer other plan letters, but they capture a very small percentage of the market.

• Plan A and B offer core, stripped-down benefits but often cost nearly as much as better plans.
• Plan K and L are cost-sharing plans where Medigap only pays 50 percent or 75 percent of the gaps until an out-of-pocket maximum is reached.
• Plan M splits the Part A hospital deductible 50/50 with you. For most beneficiaries, the clear value propositions lie firmly with Plan G and Plan N.

The Most Critical Rule: The Medigap Open Enrollment Period

Understanding the benefits of Medigap is only half the equation. Understanding when you are legally allowed to buy one is arguably the most vital piece of Medicare knowledge you will ever receive.

Unlike standard health insurance, which has an annual open enrollment every autumn, Medigap relies heavily on a single, one-time enrollment window tied directly to your aging into the system.

Your 6-Month Window

Your Medigap Open Enrollment Period (OEP) is a one-time-only window that lasts for exactly six months.

The clock begins ticking on the first day of the month in which you are both 65 years old AND actively enrolled in Medicare Part B.

During these six months, federal law grants you absolute Guaranteed Issue rights. This means any insurance carrier in Colorado must sell you any Medigap policy they offer. During this window, carriers:

• Cannot deny your application for any reason.
• Cannot charge you a higher monthly premium because of your health history, weight, or pre-existing conditions.
• Cannot impose a waiting period for coverage of pre-existing conditions.

If you have a heart condition, are actively undergoing cancer treatments, or have diabetes, your application during this six-month window will be approved immediately at the exact same price as a perfectly healthy marathon runner of the same age.

What Happens If You Miss the Window? Medical Underwriting

Once your six-month Medigap Open Enrollment Period ends, it is gone forever.

If you attempt to buy a Medigap policy, switch from one Medigap carrier to another, or drop a Medicare Advantage plan to return to Original Medicare + Medigap later in life, you are entirely subject to Medical Underwriting.

Medical underwriting means the insurance company has the legal right to ask you comprehensive questions about your health history, review your medical records, and scrutinize your prescription drug history. If the carrier determines you are too high of a financial risk, they can permanently decline your application.

Common conditions that lead to automatic declines during underwriting include:

• Current cancer treatment
• End-stage renal disease (ESRD)
• Alzheimer’s disease or dementia
• Severe COPD or emphysema
• Recent heart attacks or strokes

This makes your initial decision immensely important. Securing a Medigap policy when you first enroll in Part B locks in your coverage regardless of how your health changes down the road.

Special Circumstances: Guaranteed Issue Rights

Outside of your initial Open Enrollment window, there are a few specific, narrow life events that grant you a temporary “Guaranteed Issue” window where carriers cannot use medical underwriting against you. Common triggers include:

• You are enrolled in an employer group health plan that is terminating its coverage.
• You move out of your Medicare Advantage plan’s geographic service area.
• Your Medicare Advantage plan commits fraud or abruptly stops providing care in Colorado.
• The Trial Right: If you join a Medicare Advantage plan when you first turn 65, you have a one-time “trial period” of 12 months. If you are unhappy with the Advantage plan, you can disenroll within that first year and return to Original Medicare with a guaranteed right to buy a Medigap policy without underwriting.

If you believe you qualify for a Guaranteed Issue right, you typically have 63 days from the qualifying event to secure your Medigap policy.

Medigap Pricing Structures in Colorado

When you evaluate a Medigap quote from a carrier like Aetna Medicare, UnitedHealthcare, or Elevate Medicare Advantage, it helps to know how that premium is calculated and how it will behave as you age.

Insurance companies use one of three pricing methods to structure their Medigap premiums. The state of Colorado allows all three, but one is vastly more common than the others.

1. Attained-Age Rated (Most Common in Colorado): The premium is based on your current age (the age you have “attained”). Your premium will be lowest at age 65. As you get older, the premium automatically increases every year based simply on your advancing age, independent of overall inflation. Because this is the most common pricing structure, you should financially plan for your Medigap premium to rise steadily throughout your 70s and 80s.

2. Issue-Age Rated: The premium is based on the age you are when you first buy the policy. If you buy at 65, you pay the 65-year-old rate forever. If you wait until 70, you pay the 70-year-old rate forever. While premiums will still increase due to overall healthcare inflation, they will not increase simply because you had a birthday. These policies generally start at a slightly higher baseline price than attained-age policies.

3. Community-Rated (No-Age-Rated): Everyone who buys the policy pays the exact same monthly premium, regardless of whether they are 65 or 85. Age is entirely removed from the pricing equation. Like issue-age policies, these still go up with inflation but do not penalize you directly for aging.

Household Discounts

One of the most effective ways to lower your Medigap costs in Colorado is by taking advantage of carrier household discounts. Many insurance companies offer a substantial discount (ranging from 5% to 12%) if two people in the same home are enrolled in a Medigap policy from the exact same carrier. Some carriers are very lenient, granting the discount simply if you live with another adult over age 60, while others strictly require that both spouses hold policies with their company.

Medigap vs. Medicare Advantage (Part C) in Colorado

The single biggest crossroads you will face in Medicare is choosing between the Original Medicare + Medigap route versus a Medicare Advantage (Part C) plan. These are fundamentally opposed ways of receiving your healthcare.

It is illegal for an insurance broker or carrier to sell you a Medigap policy if you are enrolled in a Medicare Advantage plan. You must choose one track or the other.

Currently, Colorado has 103 real Medicare Advantage plans available across the state, provided by carriers like Kaiser Permanente, Clear Spring Health, Devoted Health, HealthSpring, and Perennial Advantage.

The Medicare Advantage Structure: Medicare Advantage plans are all-in-one private alternatives to Original Medicare. They bundle Part A, Part B, and usually Part D (prescription drugs) into a single plan.

• The Pros: Advantage plans often advertise a $0 monthly premium. They also frequently include extra benefits that Original Medicare lacks, such as routine dental cleanings, vision exams, and hearing aids.
• The Cons: In exchange for the low upfront premium, you agree to navigate the carrier’s localized HMO or PPO networks. If a doctor is out-of-network, you may pay significantly more or receive no coverage at all. You also pay as you go through copays for doctor visits, hospital stays, and tests, up to an annual maximum out-of-pocket limit (which can be as high as $8,000+). You must also deal with prior authorizations, meaning the insurance company must approve expensive treatments before your doctor can perform them.

The Medigap Structure: Medigap takes the opposite approach.

• The Pros: Unmatched freedom and predictability. You can see any doctor in the country who accepts Original Medicare. You do not need referrals. You rarely deal with prior authorizations. If you have a Plan G, your out-of-pocket medical costs are capped at the small Part B annual deductible.
• The Cons: You pay a higher, guaranteed monthly premium upfront. You do not receive free dental, vision, or hearing benefits, and you must purchase your prescription drug coverage separately.

For seniors in Colorado who travel frequently out of state, split time between a summer and winter home, or value the peace of mind of knowing their medical bills are essentially zeroed out in the event of a catastrophic illness, Medigap remains the gold standard.

Do You Need a Separate Part D Prescription Drug Plan?

Yes. It is critical to note that modern Medigap policies (sold after 2006) do not cover retail prescription drugs. Medigap only covers medical services and hospitalizations (such as medications administered via IV in a hospital or clinic setting under Part B).

When you purchase a Medigap policy, you must also purchase a standalone Medicare Part D prescription drug plan to cover the medications you pick up at the pharmacy.

Even if you do not currently take any prescription medications, you should strongly consider enrolling in a low-cost Part D plan. If you go 63 days or more without “creditable” prescription drug coverage after turning 65, the federal government will penalize you. The Part D late enrollment penalty is calculated as 1% of the national base beneficiary premium for every month you lacked coverage. This penalty is permanently added to your monthly Part D premium for the rest of your life.

How to Choose a Medigap Carrier in Colorado

Since the federal government guarantees that a Plan G from UnitedHealthcare has the identical medical benefits as a Plan G from Select Health, how do you decide which company gets your business?

When benefits are equal, your decision should rest on these three pillars:

1. Current Premium & Rate Stability: Look at the starting price, but more importantly, investigate the carrier’s history of rate increases in Colorado over the last three to five years. A carrier that prices a policy aggressively low to attract 65-year-olds but has a history of 10% annual rate hikes will cost you far more in the long run than a carrier that starts slightly higher but maintains stable 3% increases.
2. Financial Strength: Look for carriers with strong A.M. Best or Standard & Poor’s ratings. You want a company with the financial reserves to pay claims seamlessly and weather economic downturns without passing the burden to you via massive premium spikes.
3. Household Discounts: If you are married and your spouse is also eligible for Medicare, the carrier offering a generous 10% household discount may instantly become your most mathematically sound option, even if their base rate was slightly higher.

Actionable Next Steps: Your Colorado Medicare Decision Framework

Making your transition to Medicare shouldn’t feel like guesswork. If you are approaching age 65 or preparing to retire and lose employer coverage, follow this direct sequence:

1. Verify Your Part B Enrollment: Ensure you are actively enrolled in both Part A and Part B. You cannot purchase a Medigap policy without holding both.
2. Commit to the Medigap Track: Decide firmly whether you want the network freedom and flat predictability of Medigap, or the local networks and pay-as-you-go structure of Medicare Advantage.
3. Select Your Letter: Evaluate your budget and risk tolerance. If you want maximum protection and zero medical bills, select Plan G. If you are comfortable paying small copays for doctor visits in exchange for a lower premium, select Plan N.
4. Compare Colorado Carriers: Review quotes from reputable carriers in the state. Factor in their financial ratings, rate increase history, and applicable household discounts.
5. Add Part D: Secure a standalone prescription drug plan to avoid federal late penalties.

Your initial enrollment window is the most powerful leverage you have in the Medicare system. Use that time wisely to secure the long-term coverage that best protects your health and your financial legacy.

Frequently Asked Questions