Turning 65 on the Gulf Coast triggers one of the most consequential health insurance transitions of your life. Medicare involves multiple enrollment periods, permanent penalties for missing deadlines, and a decision between coverage structures that is difficult to reverse later. This guide walks you through every step of the transition — from your Initial Enrollment Period through Part D and the Medigap vs. Medicare Advantage decision.
Your Initial Enrollment Period (IEP) for Medicare Parts A and B is a 7-month window: the 3 months before your 65th birthday month, your birthday month itself, and the 3 months after. For someone turning 65 in August, the IEP runs May through November.
When your coverage starts depends on when you enroll within the IEP:
Enroll as early as possible in the IEP — ideally in the 3 months before your birthday — to have coverage start with no gap.
Most people are eligible for premium-free Part A (hospital insurance) based on their work history. If you or your spouse paid Medicare taxes for at least 40 quarters (10 years), your Part A premium is $0. You should generally enroll in Part A at 65 even if you plan to delay Part B.
Part B (outpatient medical coverage) carries a standard premium of $185/month in 2026 for most beneficiaries. Higher earners pay more through IRMAA surcharges (see below). Part B covers doctor visits, outpatient procedures, lab tests, preventive services, and durable medical equipment.
The late enrollment penalty for Part B is 10% of the premium for each full 12-month period you were eligible but did not enroll — and it applies for life. A two-year delay without creditable coverage means a 20% permanent surcharge. At $185/month base, that adds $37/month every month for the rest of your life.
If you are covered by an employer-sponsored group health plan at age 65 and your employer has 20 or more employees, your employer plan is the primary insurer and Medicare is secondary. You can delay Part B enrollment without penalty in this situation.
When you eventually retire or lose that employer coverage, you have an 8-month Special Enrollment Period to enroll in Part B without penalty. Do not wait more than 8 months after losing that coverage, or the late enrollment penalty applies.
If your employer has fewer than 20 employees, Medicare becomes the primary payer at 65. You should enroll in Part B at your IEP even if you are still working.
If you are on an ACA marketplace plan when you turn 65, you must transition to Medicare. You cannot receive Advance Premium Tax Credits (APTCs) while enrolled in Medicare. If you keep both and continue collecting marketplace subsidies after Medicare enrollment, you will owe repayment of those credits at tax time.
To disenroll from your marketplace plan, log in to your healthcare.gov account (or state marketplace) and submit a voluntary disenrollment. Give at least 30 days notice to align your marketplace plan end date with your Medicare start date. Confirm that your Medicare coverage has actually started before your marketplace plan terminates.
This catches many people off guard. Once you enroll in any part of Medicare — including Part A — you can no longer make contributions to a Health Savings Account (HSA). Part A enrollment retroacts up to 6 months before the date you apply (unless it would go back before age 65). If you apply for Medicare and Part A retroacts 6 months, you may be deemed to have been ineligible to contribute to your HSA for those prior months.
Best practice: stop HSA contributions at least 6 months before you plan to apply for Medicare. You can still spend existing HSA funds tax-free on Medicare premiums, deductibles, and other qualified medical expenses — the HSA balance does not disappear, you simply cannot add to it.
High-income Medicare beneficiaries pay an Income-Related Monthly Adjustment Amount (IRMAA) on top of their standard Part B and Part D premiums. IRMAA is based on your income from two years prior (2026 premiums are based on 2024 tax returns). Surcharges in 2026 range from approximately $70/month additional to over $450/month additional for the highest income bracket.
If your income in 2024 was unusually high due to a one-time event (sale of property, Roth conversion, retirement distribution), you can appeal IRMAA with SSA using Form SSA-44 if a "life-changing event" has since reduced your income. Retiring is a qualifying life-changing event for IRMAA appeals.
This is the most consequential choice in the Medicare transition. Understanding the trade-offs is essential before you commit.
The timing trap: At 65, you have guaranteed issue rights for Medigap — meaning no insurer can deny you or charge more based on your health history. If you enroll in Medicare Advantage first and later want to switch to Medigap, you generally must pass medical underwriting (in most states, including FL, TX, AL, MS, and LA). If you develop a serious condition in the interim, you may be uninsurable for Medigap. Choose carefully at 65.
Part D prescription drug coverage carries a late enrollment penalty of 1% of the national base beneficiary premium for each month you go without creditable drug coverage. This penalty is permanent and compounding. At 65, even if you take no prescriptions, enrolling in a low-cost Part D plan protects you from a future penalty when you do need drug coverage.
Low-cost Part D plans in Gulf Coast markets are available from $10–$25/month. Choose a plan whose formulary covers your current medications, and review it during Annual Election Period (October 15 – December 7) each year as formularies change.