The single most important decision in your Medicare journey isn’t which plan to buy. It’s when to buy it.
Medicare Supplement insurance — also known as Medigap — has a one-time enrollment window that most people don’t fully understand until it’s too late. Buying during that window can save you thousands of dollars over your retirement and guarantee you access to coverage regardless of your health. Missing it can limit your options permanently.
Here’s what you need to know about the timing.
The short answer: buy at 65
For most people, the best time to buy a Medicare Supplement plan is the moment you become eligible — at age 65, during your Medigap Open Enrollment Period.
That window opens the first day of the month you turn 65 and are enrolled in Medicare Part B, and it lasts exactly six months. During those six months, you have rights that you will likely never have again.
If you take only one thing away from this article, let it be this: the easiest, cheapest, and most flexible time to buy a Medigap plan is during your initial six-month window. Everything else in this article is an explanation of why.
What the Medigap Open Enrollment window gives you
During your initial six-month enrollment window, three things are true that may never be true again:
You cannot be denied coverage. Any Medigap plan available in your state must be sold to you regardless of your health history. No medical underwriting. No questions about preexisting conditions. No denials.
You cannot be charged more for your health. The premium you’re quoted is the same premium a perfectly healthy applicant in your age and zip code would pay. Insurers cannot mark up your rate because of diabetes, heart disease, cancer history, or anything else in your medical record.
You have your full choice of plans. Every Medigap plan offered in your state is on the table — Plan G, Plan N, Plan F if you were eligible before 2020, high-deductible options, all of them. You pick what works best for you, not what you can qualify for.
That combination of rights — guaranteed issue, no health-based pricing, and full plan selection — is rare in the insurance market. Most coverage you buy at any age is subject to underwriting. Medigap during your initial window is not.
What happens if you wait
Once your six-month window closes, the rules change significantly in most states.
Insurance companies are allowed to medically underwrite you, which means they can review your health history and make decisions based on it. They can deny your application outright. They can offer coverage but only at a higher premium. They can refuse to cover certain plans for someone with your health profile.
If you developed any significant health condition between turning 65 and finally deciding to enroll — a heart attack, a cancer diagnosis, diabetes, COPD, even something that feels minor like high blood pressure — your options can narrow dramatically.
The cruel irony is that the people most likely to delay the decision are often the people who can least afford to. Someone in good health at 65 who waits a few years often still qualifies easily. Someone with developing health issues at 65 who waits faces the real possibility of being locked out of the comprehensive coverage they need most.
The exceptions: guaranteed issue rights
Federal law provides a few specific situations after your initial enrollment window where you keep guaranteed issue rights — meaning insurers must sell to you without underwriting. These include:
Losing employer or union coverage that was supplementing your Medicare. Your Medicare Advantage plan leaving your service area or terminating. Your Medigap insurance company going bankrupt. Trial right scenarios where you tried Medicare Advantage for the first time and want to switch back to Original Medicare with Medigap within 12 months.
These protections are narrow and time-limited. If you fall into one of them, you typically have 63 days to enroll in a Medigap plan without underwriting. Outside of these specific scenarios, you’re back in underwriting territory.
State-specific protections
A handful of states have laws that go beyond federal protections and give residents additional rights to switch or buy Medigap plans without underwriting. These vary significantly in how they work.
California, Oregon, Missouri, Idaho, Illinois, and Nevada have versions of what’s called the Medicare Birthday Rule, which lets current Medigap holders switch to an equal or lesser plan around their birthday each year without medical underwriting.
New York and Connecticut require year-round guaranteed issue for Medigap, meaning residents can buy or switch plans at any time without underwriting.
Maine, Massachusetts, and Washington have their own variations of continuous or annual open enrollment windows for Medigap.
These state protections are valuable but limited. They typically only allow switching between certain plans — not necessarily an upgrade to a more comprehensive option without underwriting. If you live in one of these states, an independent broker can tell you exactly what rights you have and how to use them.
The long-term cost difference
Here’s where the financial math becomes clear.
A 65-year-old buying Plan G during their Open Enrollment Period might pay around $130 to $180 per month depending on the carrier and state. That same person at 70, after underwriting, might still qualify and pay a similar premium adjusted for age — but if their health has changed, they could be facing a 30 to 50 percent rate-up, or be limited to less comprehensive plans.
Over a 20-year retirement, the difference between locking in optimal coverage at 65 and being limited by underwriting later can easily reach $20,000 to $40,000 in additional premiums and out-of-pocket costs.
That math doesn’t even account for the peace of mind. Knowing your coverage is locked in regardless of what happens to your health is itself worth something.
What about people still working at 65?
This is one of the most common questions we get, and the answer depends on your specific situation.
If you have employer-sponsored health insurance through an employer with 20 or more employees, you can typically delay enrollment in Part B and the Medigap window without penalty. When you eventually retire or lose that employer coverage, you get a Special Enrollment Period that includes Medigap guaranteed issue rights.
If your employer has fewer than 20 employees, Medicare becomes your primary insurance at 65 whether you’re working or not, and delaying enrollment can result in penalties and gaps in coverage. This scenario requires a careful conversation about timing.
For most people in larger employer plans, delaying Medigap until you actually retire is a reasonable strategy — as long as you understand the rules and don’t accidentally miss your guaranteed issue window when employment coverage ends.
What to do at 65
A few practical steps to make sure you don’t miss your window:
Enroll in Part B on time. Your Medigap Open Enrollment Period starts when you’re enrolled in Part B. If you delay Part B without qualifying for a Special Enrollment Period, you’re delaying your Medigap window — and you may incur lifetime late enrollment penalties.
Compare plans across multiple carriers. Medigap plans are standardized — Plan G from one carrier covers the same things as Plan G from any other carrier. But the premiums vary significantly. The same Plan G can cost $40 to $80 more per month depending on which carrier you choose. Shopping matters.
Think long-term, not just first-year cost. The cheapest premium today isn’t always the best deal over 20 years. Some carriers raise rates faster than others, and a slightly higher initial premium can result in lower lifetime costs.
Get help from an independent broker. Captive agents can only sell one company’s plans. An independent broker represents multiple top-rated carriers and can compare them side by side — without bias toward any particular company.
Get your free Medicare review today
At Term Insurance Brokers, we help clients navigate the Medigap decision every day. We represent multiple top-rated carriers and walk you through the comparison without pressure, with the full picture of what’s available in your state.
There’s no cost for a Medicare review and no obligation to enroll. We do the comparison work — you make the call.
Call us at 703-665-9133 or visit our contact page for your free Medicare consultation today.
Term Insurance Brokers is an independent brokerage licensed in 35+ states. We are not affiliated with any single insurance company.