Comparing Medicare plans in Colorado
Medicare Part B is the medical insurance component of Original Medicare. If Part A is your “hospital insurance” that covers you when you are formally admitted as an inpatient, Part B is your “walking around” insurance. It covers everything else: the doctors you see, the outpatient surgeries you undergo, the preventive screenings you schedule, and the medical equipment you use at home. If a medical service happens outside of a formal hospital admission, Part B is almost certainly the part of Medicare paying the bill.
Understanding how Part B functions is critical because, unlike Part A, it is not free, and it is not entirely comprehensive on its own. It requires a monthly premium, carries an annual deductible, and leaves you with an uncapped 20% coinsurance bill for your medical care. Whoever is reading this needs to understand not just what Part B covers, but the financial mechanics of how it bills you, when exactly you are supposed to enroll, and how it interacts with private insurance options in Colorado.
This guide serves as your complete, foundational resource for understanding Medicare Part B in Colorado, designed to help you make informed decisions about your enrollment, your coverage, and your financial protection.
According to the Centers for Medicare & Medicaid Services (CMS), Part B covers two broad categories of medical services: medically necessary services and preventive services.
Medically necessary services are the tests, supplies, and interventions needed to diagnose or treat a medical condition. Preventive services are the screenings, counseling sessions, and shots aimed at preventing illnesses entirely or detecting them at an early stage when treatment is most likely to work.
Part B covers your routine visits to a primary care physician, as well as appointments with specialists like cardiologists, neurologists, dermatologists, and endocrinologists. Under Original Medicare, you do not need a referral from a primary care doctor to see a specialist, provided the specialist accepts Medicare. This gives beneficiaries immense freedom to seek care from experts across Colorado or even across the country.
Major medical procedures are increasingly moving out of the hospital and into specialized outpatient facilities. Part B covers services you receive in an emergency room, observation services in a hospital (when you are not formally admitted as an inpatient), and surgeries performed in ambulatory surgery centers. Whether you are getting a knee scoped in an ambulatory surgery center in Denver or having cataract surgery in Aspen, Part B is the insurance component that handles the facility fees and the surgeon’s professional fees.
Medicare places a strong emphasis on preventive care, often covering these services at 100% (meaning no out-of-pocket cost to you) if you see a healthcare provider who accepts assignment. Covered preventive services include:
If your doctor prescribes medical equipment for use in your home, Part B covers it. This category is broad and includes blood sugar monitors, test strips, infusion pumps, oxygen equipment, CPAP machines, wheelchairs, and walkers. To get this coverage, both your doctor and the equipment supplier must be officially enrolled in Medicare.
Part B provides coverage for outpatient mental health care. This includes visits with a psychiatrist, clinical psychologist, clinical social worker, or clinical nurse specialist. It covers individual and group psychotherapy, psychiatric evaluation, medication management, and partial hospitalization programs (which offer intensive outpatient psychiatric care).
In an emergency, Part B covers ground ambulance transportation to a hospital, critical access hospital, or skilled nursing facility when traveling in any other vehicle could endanger your health. In severe, rapid-response situations, it may also cover airplane or helicopter ambulance services, though the criteria for air transport are strictly regulated and highly scrutinized.
Part B covers blood tests, urinalysis, tissue pathology, and other laboratory tests ordered by your doctor. Under Original Medicare, these lab tests are generally covered in full with no deductible or coinsurance required from the patient.
One of the most common points of confusion for Colorado seniors navigating Part B involves the difference between a “preventive” service and a “diagnostic” service. This distinction has profound financial consequences.
By law, Part B fully covers certain preventive screenings. However, if a screening reveals an abnormality, or if you report symptoms that prompt your doctor to investigate further, the service shifts from preventive to diagnostic. When it becomes diagnostic, Medicare’s standard cost-sharing rules—meaning deductibles and a 20% coinsurance—immediately apply.
The classic example is a colonoscopy. If you are due for a routine, preventive colonoscopy, Medicare covers it at 100%. However, if the gastroenterologist finds and removes a polyp during that procedure, the procedure legally transforms from a preventive screening to a diagnostic intervention. You will suddenly be responsible for paying 20% of the Medicare-approved amount for the doctor’s services and the facility fee.
Understanding this mechanism helps prevent billing surprises. If you go in for a “free” Medicare Annual Wellness visit but ask your doctor to examine a new, painful lump on your shoulder, the doctor will bill Medicare for both a wellness visit and a diagnostic medical exam. You will receive a bill for the diagnostic portion.
Medicare Part B is not free. It is a shared-cost system where you pay a monthly premium to maintain the coverage, an annual deductible before the coverage begins paying for most services, and a percentage of the bill for the care you receive.
| Cost Category | How it Works | Financial Impact | Notes |
|---|---|---|---|
| Monthly Premium | Paid every month to the federal government. | Base rate for most; higher earners pay more via IRMAA. | Often deducted directly from Social Security checks. |
| Annual Deductible | The amount you pay out-of-pocket for medical services before Part B begins to pay. | A relatively small, flat annual figure set by CMS. | Resets every year on January 1st. |
| Coinsurance | Your share of the cost for a covered service after meeting the deductible. | You pay 20% of the Medicare-approved amount. | There is no annual cap on this 20% liability. |
Most beneficiaries pay the standard Part B premium. This amount is calculated and published annually by CMS. If you receive Social Security retirement benefits, the government will automatically deduct this premium from your monthly check. If you do not yet draw Social Security, you will receive a quarterly bill from Medicare.
However, if your modified adjusted gross income (MAGI) exceeds certain thresholds, you will pay the standard premium plus an Income-Related Monthly Adjustment Amount (IRMAA). Medicare looks at your IRS tax return from two years prior to determine if IRMAA applies. For example, your Part B premium for 2026 would be based on the income reported on your 2024 tax return. IRMAA is organized into brackets; the higher your income, the higher your monthly surcharge. If your income has recently dropped due to a qualifying life event—such as retiring, losing a pension, or the death of a spouse—you can file an appeal with the Social Security Administration using form SSA-44 to have your IRMAA reduced or eliminated.
Before Original Medicare pays its share for your doctor visits and outpatient care, you must satisfy an annual Part B deductible. This is a relatively small threshold that resets every January 1st. You pay 100% of your non-preventive medical bills out of pocket until this amount is met for the year.
Once your annual deductible is met, Original Medicare generally covers 80% of the Medicare-approved amount for medically necessary services. You are responsible for the remaining 20%.
This is the most critical financial reality of Original Medicare: The 20% coinsurance has no out-of-pocket maximum.
If you visit a primary care doctor for a mild illness, 20% of a $150 bill is $30—a manageable expense. But if you are diagnosed with cancer and require expensive outpatient chemotherapy, or if you need a major outpatient surgery, that 20% liability scales up infinitely. If an outpatient procedure and facility fees total $50,000, your 20% share is $10,000.
Because of this catastrophic financial risk, very few Coloradans rely on Original Medicare alone. They either purchase a Medicare Supplement (Medigap) policy to pay that 20% coinsurance, or they enroll in a Medicare Advantage (Part C) plan to replace the uncapped 20% with predictable, capped copayments.
A Medicare Advantage plan (Part C) is an alternative way to receive your Medicare benefits. These plans are offered by private, Medicare-approved insurance companies. When you join a Medicare Advantage plan, the private carrier takes on the responsibility of administering your Part A and Part B benefits.
One of the most widespread misconceptions about Medicare Advantage is that it replaces the Part B premium. It does not. To enroll in and keep a Medicare Advantage plan in Colorado, you must continue to pay your Part B premium to the federal government. If you stop paying your Part B premium, you will be disenrolled from your Medicare Advantage plan and returned to Original Medicare.
Colorado’s Medicare Advantage market is robust, with 103 real Medicare plans available across the state depending on your specific county. Carriers operating in Colorado include:
These private carriers organize their Part B services into structured networks, most commonly Health Maintenance Organizations (HMOs) or Preferred Provider Organizations (PPOs).
For example, UnitedHealthcare offers plans like the AARP Medicare Advantage from UHC CO-0013 (PPO) and the AARP Medicare Advantage Essentials from UHC CO-2 (HMO-POS). In an HMO-style plan, you generally must use doctors and hospitals within the plan’s specific network to receive coverage, except in emergencies. In a PPO-style plan, you have the flexibility to see out-of-network doctors for Part B services, but you will typically pay a higher share of the cost when you do.
Instead of the uncapped 20% coinsurance you face under Original Medicare, Medicare Advantage plans translate Part B services into flat copays (e.g., $10 to see a primary care doctor, $40 to see a specialist, or $250 for outpatient surgery). Most importantly, federal law mandates that all Medicare Advantage plans include a strict annual out-of-pocket maximum, protecting you from catastrophic Part B costs.
Enrolling in Part B is highly dependent on timing. Missing your designated enrollment window can result in lifelong financial penalties and delayed coverage. Medicare operates on specific, inflexible enrollment periods.
Your first opportunity to enroll in Part B is your Initial Enrollment Period. This is a 7-month window structured around your 65th birthday. It includes:
If you are already receiving Social Security retirement benefits or Railroad Retirement Board benefits when you turn 65, the government will automatically enroll you in both Part A and Part B. Your red, white, and blue Medicare card will arrive in the mail about three months before your birthday. If you do not want Part B (perhaps because you are still working and covered by an employer plan), you must follow the instructions on the back of the card to actively decline it.
If you are not yet drawing Social Security, you will not be automatically enrolled. You must proactively contact the Social Security Administration (online, by phone, or in person) during this 7-month IEP window to sign up.
Many Coloradans continue working well past their 65th birthday. If you (or your spouse) are actively employed and you have “creditable” health insurance through that employer, you do not have to enroll in Part B right away. You can delay it without penalty.
Once that employment ends or that employer health coverage ends (whichever happens first), a Special Enrollment Period (SEP) begins. This SEP gives you a strict 8-month window to enroll in Part B without facing late penalties. To use this SEP, you and your employer will need to fill out CMS Form L564 to prove to the government that you had qualifying coverage since turning 65.
If you missed your IEP and you do not qualify for a Special Enrollment Period, you are restricted to the General Enrollment Period. The GEP runs from January 1st through March 31st of every year. If you sign up during the GEP, your Part B coverage will begin the first day of the month after you enroll. However, using the GEP almost always means you will face a late enrollment penalty.
The federal government uses a financial penalty to ensure people sign up for Part B when they are first eligible, rather than waiting until they get sick to buy insurance.
If you do not sign up for Part B when you are first eligible and you do not have qualifying creditable coverage (like a large employer group health plan), your monthly Part B premium will go up 10% for each full 12-month period you could have had Part B but did not sign up.
For example, if you waited two full years (24 months) to sign up for Part B after your IEP ended, and you didn’t have employer coverage, your penalty would be 20% (10% x 2 years). This 20% surcharge is added to the standard Part B premium.
Crucially, this penalty is not a one-time fee; it lasts for the rest of your life. You will pay that extra 20% every single month for as long as you have Medicare Part B. Avoiding this lifetime penalty is one of the most important reasons to fully understand your enrollment timelines.
If you are 65, actively working, and covered by a group health plan, the decision to take or delay Part B depends entirely on the size of the employer providing the coverage.
If you get your insurance from an employer with 20 or more employees, the employer’s group health plan is considered the “primary” payer. Medicare is considered “secondary.” In this scenario, your employer coverage pays your medical bills first. Because you have primary, creditable coverage, you can safely delay enrolling in Medicare Part B until you retire or lose that coverage, and you will not face a late penalty later.
If you get your insurance from a small employer (fewer than 20 employees), the rules flip. Medicare automatically becomes the primary payer at age 65, and the employer’s plan becomes secondary.
In this scenario, you must enroll in Medicare Part B as soon as you turn 65. If you fail to enroll, your employer’s insurance company is legally permitted to refuse payment on 80% of your outpatient medical bills, arguing that Medicare should have paid that portion. You would be left entirely responsible for that debt.
If you answer "Yes" to all of the following, you can generally delay Part B without penalty.
If you remain on Original Medicare (meaning you do not join a Medicare Advantage plan), you have the freedom to see any doctor or specialist in the United States who accepts Medicare. However, how a doctor interacts with the Medicare system dictates how much you will pay for their services. There are three classifications of doctors under Part B.
These doctors have signed an agreement to accept the Medicare-approved amount as payment in full for their services. This is called “accepting assignment.” When you see a participating provider, you pay nothing for covered preventive care, and you pay exactly 20% of the Medicare-approved amount for diagnostic and necessary care after meeting your deductible. This is the safest and most cost-effective way to use Part B.
These doctors have not signed an agreement to accept the Medicare-approved amount as full payment, but they still take Medicare patients. They are legally allowed to charge you up to 15% more than the standard Medicare-approved amount for a service. This 15% surcharge is known as the “Medicare Limiting Charge.”
If you see a non-participating doctor, you will be responsible for your standard 20% coinsurance plus the extra 15% limiting charge. Furthermore, the doctor may ask you to pay the entire bill upfront, requiring you to submit a claim to Medicare yourself to get reimbursed for Medicare’s share.
Some doctors and psychiatrists in Colorado have formally opted out of the Medicare system entirely. They will not bill Medicare, and Medicare will not pay them. If you choose to see an opt-out provider, you must sign a private contract agreeing to pay whatever rates the doctor sets out of your own pocket. Medicare will not reimburse you for any portion of these services.
As surgical technology advances, procedures that used to require a multi-day hospital stay—like knee replacements, hernia repairs, and certain cardiac catheterizations—are now safely performed in outpatient facilities. Part B is responsible for the billing in these scenarios.
When you use an outpatient facility, such as an Ambulatory Surgery Center, Part B covers both the facility fee (the cost of the operating room, nurses, and equipment) and the professional fee (the surgeon’s time and expertise). You will owe the Part B deductible and the 20% coinsurance for both bills. Ensuring that the facility itself is Medicare-approved is just as important as ensuring the surgeon accepts Medicare assignment.
Medicare Part B recognizes the critical importance of mental health and provides substantial coverage for outpatient treatment. This includes visits with psychiatrists, clinical psychologists, and licensed clinical social workers. Part B pays for individual psychotherapy, group therapy, family counseling (if the primary purpose is your treatment), and medication management.
In recent years, CMS has significantly expanded Part B telehealth benefits. For mental health services, counseling, and substance use disorder treatment, you can receive care via telehealth (video or audio-only phone calls) from the comfort of your home, without geographical restrictions. Standard Part B deductibles and coinsurance rules apply to these virtual visits exactly as they would for in-person appointments.
If you receive a service that you believe should be covered by Part B, but Medicare denies the claim, you have the right to appeal the decision. Medicare has a structured, five-level appeals process:
Most routine billing errors or miscoded diagnostic services are resolved at the first level of redetermination by simply having your doctor’s office submit corrected paperwork to prove the service was medically necessary.
Medicare Part B is the workhorse of your medical insurance, handling the day-to-day interactions you have with the healthcare system in Colorado. Because it carries an uncapped 20% financial liability and strict enrollment penalties, treating it as an automated, hands-off benefit is a mistake.
You must make deliberate choices: determining if you can safely delay enrollment based on employer size, choosing between a Medigap policy to cover the 20% liability or a Medicare Advantage plan to cap it, and ensuring your chosen providers accept Medicare assignment. By understanding the mechanics outlined in this guide, you can navigate Part B efficiently, protect your financial assets, and ensure you receive the outpatient care you need.
Speak with a licensed producer to compare Medicare Advantage and Medigap options that protect against Part B costs in your specific Colorado county.
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