Your initial enrollment window
It begins three months before the month you are first entitled to both Part A and Part B, and runs through the later of the end of the second month after that month, or the end of your Part B initial enrollment period.
Moon Insurance Managers, Inc. · TDI license #5595
Medicare
Moon Insurance Managers, Inc. is a private, independent insurance agency in Houston. We are not Medicare. We are not the Centers for Medicare & Medicaid Services, the Department of Health and Human Services, or any government agency, and this page is not a government publication.
We wrote that first because it is true and because you should know who is talking before you read anything else about a federal program.
This page explains how Medicare is put together and when you can enroll. It does not show you plans, prices or comparisons — there is a reason for that, and it is at the bottom of the page.
42 CFR Election and benefit periods
Dates and limits fixed in regulation
- Election periods
- § 422.62
- Qualifying hospital stay
- Three days, § 409.30
- Admission window
- 30 days after discharge
- Skilled nursing
- 100 days per benefit period
- Coinsurance from
- Day 21
Agent of record
The parts, as structure
How Medicare is put together
Medicare is a federal health insurance program. Most people become eligible at 65, but that is not the only route: people under 65 can qualify through disability, and separate rules apply for end-stage renal disease (ESRD) and amyotrophic lateral sclerosis (ALS).
It is built in parts, and the parts are structural rather than a menu of products.
The parts, and what each one is
- Part A — hospital insurance Inpatient hospital care, some skilled nursing facility care after a hospital stay, hospice, and some home health care
- Part B — medical insurance Doctor visits, outpatient care, preventive services, durable medical equipment, and most care that does not happen as a hospital inpatient
- Part C — Medicare Advantage Not a benefit of its own but a different delivery route: private plans approved to provide your Part A and Part B coverage in place of Original Medicare
- Part D — prescription drug coverage Offered through private plans
- Medicare supplement — Medigap Something else again: a private policy that works alongside Original Medicare rather than replacing how you receive it, sold in standardized plan letters and regulated by the states
Part A and Part B together are what people mean by Original Medicare.
One structural point about how the two private routes are usually packaged, because it decides what else you have to arrange: Medicare Advantage plans commonly include drug coverage in the plan itself. A Medicare supplement does not — it works alongside Original Medicare and pays toward cost sharing, so somebody on Original Medicare plus a supplement generally needs a separate Part D plan for drugs, arranged elsewhere. We say so because a page that walks somebody into a supplement without mentioning it has left them one plan short.
The one structural point worth holding on to: Medicare Advantage and Medicare supplement are not two versions of the same thing. One replaces how you receive Original Medicare; the other sits beside it. Which is right for a particular person is a real conversation, and it is a conversation, not a web page.
Fixed in federal regulation
When you can enroll
Medicare enrollment runs on fixed windows. These are set in federal regulation and they do not change from year to year.
October 15 to December 7 — the annual election period
In this window you can move from a Medicare Advantage plan to Original Medicare, from one Medicare Advantage plan to another, or from Original Medicare to a Medicare Advantage plan.
January 1 to March 31 — the Medicare Advantage open enrollment period
Read this one carefully. It is available only to people already enrolled in a Medicare Advantage plan, and it allows one change: to a different Medicare Advantage plan, or out to Original Medicare. If you are on Original Medicare, you cannot use this window to join a Medicare Advantage plan. This is probably the most commonly misstated fact in Medicare marketing, and every January somebody acts on the wrong version of it.
Other enrollment paths exist — special enrollment periods tied to circumstances like leaving employer coverage, and rules about late enrollment penalties. They depend on individual facts, they are the part most often got wrong second-hand, and the right place to establish yours is Medicare.gov or 1-800-MEDICARE.
Source: 42 CFR § 422.62 — election periods. Verified .
State-regulated, and local
Two Texas rules you were probably not told
Medicare supplement policies are regulated by the state, which means Texas has rules a national website will not tell you about. Two of them change outcomes.
If you are under 65 and have Medicare because of a disability
In Texas you have a six-month Medicare supplement open enrollment period beginning the day you enroll in Medicare Part B — but that open enrollment right applies only to Plan A.
And you get a second open enrollment period during the first six months after you turn 65. In that second window you can buy any Medicare supplement plan available in the market, at the same rates charged to anyone else enrolling at 65.
That second sentence is why this section exists. Somebody who went onto Medicare at 52 through disability, bought the only plan available to them, and was never told anything more will stay on Plan A for the rest of their life. The door opens again at 65, and it is only open for six months.
If you are under 65 with ESRD or ALS
Since September 1, 2025, a Texas Medicare supplement issuer must offer an individual under 65 who qualifies for Medicare with end-stage renal disease or ALS the same coverage it offers people 65 and over — at the same rates for Plans A, B and D, and at no more than 200% of standard rates for other plans — with no medical underwriting, no waiting period and no pre-existing condition limitation.
One more Texas-adjacent fact worth knowing: Plans C, F and high-deductible F are not available to people who first became eligible for Medicare on or after January 1, 2020. If somebody recommends one to you and you turned 65 after that date, something is wrong with the recommendation.
Sources: TDI — Medicare supplement insurance guide; HB 2516, 89th Reg. Sess. (2025); TDI Bulletin B-0010-25. Verified .
The costly misconception
Medicare and long-term care
This is the misconception that costs families the most, so here is the actual rule.
Medicare covers post-hospital skilled nursing facility care. It requires an inpatient hospital stay of at least three consecutive calendar days, not counting the discharge day, and admission to the facility within 30 calendar days of leaving the hospital. It runs up to 100 days in a benefit period, with a daily coinsurance from the 21st day through the 100th.
That is skilled care after a hospitalization, and it is finite. It is not long-term care coverage. Custodial care — ongoing help with the activities of daily living, whether or not there was ever a hospital stay — is a different problem with a different answer, and our long-term care insurance page covers it properly.
Sources: 42 CFR § 409.30 — qualifying hospital stay; 42 CFR § 409.61 — benefit period limits. Verified .
Better first stops than us
Where to get the complete picture, for free
We are naming these on our own page on purpose, because they are better first stops than we are:
- Medicare.gov and 1-800-MEDICARE — the complete source of your options, every plan available where you live, and the current year’s costs.
- HICAP — the Texas Health Information, Counseling and Advocacy Program. Free benefits counselling from someone who is not selling you anything: the state trains and oversees the counsellors, and no carrier pays them. Reach it on the Texas Medicare Help Line, 800-252-9240.
If your question is what are all of my options, one of those is the right call, not us.
A decision, not an oversight
What this page will not do, and why
We do not publish plan names, plan benefits, prices, cost sharing or comparative ratings on this page. That is a deliberate decision and not an oversight.
Medicare plan marketing is closely regulated. Material that discusses a plan’s benefits, costs or comparative ratings is subject to federal review requirements, and it has to come from a licensed agent who holds the appointments and current certifications for the specific plans being discussed. A web page that publishes plan comparisons is doing something that ought to happen in a supervised conversation, where somebody can be asked follow-up questions and be held responsible for the answer.
We would also rather you had the complete picture than our slice of it, which is what Medicare.gov and 1-800-MEDICARE are for.
What we can do is explain how the program is put together, tell you which windows you are in, and — if you want a Texas Medicare supplement conversation — have it with you on the phone, where it belongs.
No form on this page
Talk it through
Call (281) 484-8320 if you want to talk through where you are in the process. There is no form on this page, and that is deliberate: nothing here enrolls anybody in anything, and an enrolment-shaped form does not belong on a page whose job is to explain a federal program.
Moon Insurance Managers, Inc. · 360 FM 1959, Houston, TX 77034 · (281) 484-8320 · Texas Department of Insurance license #5595
Questions people ask
Are you Medicare, or connected to it?
No. Moon Insurance Managers, Inc. is a private independent insurance agency. We are not Medicare, CMS, HHS or any government agency, and nothing on this page is endorsed or approved by them.
Can I switch from Original Medicare to a Medicare Advantage plan in January?
No. The January 1 to March 31 window is only for people already enrolled in a Medicare Advantage plan, and it allows one change. Joining from Original Medicare happens in the October 15 to December 7 window, or through a special enrollment period if you qualify.
I am under 65 and on Medicare because of a disability. Can I buy a Medicare supplement?
In Texas, yes — with a six-month open enrollment beginning when you enroll in Part B, though that right applies only to Plan A. And you get a second open enrollment during the first six months after you turn 65, when every plan in the market becomes available to you at ordinary age-65 rates.
If I take a Medicare supplement, am I covered for prescriptions?
Generally not by the supplement itself. A Medicare supplement pays toward what Original Medicare leaves you; drug coverage is Part D, and on that route it is a separate plan you arrange elsewhere. Medicare Advantage plans commonly include drug coverage in the plan. Establish which route you are on before you assume prescriptions are handled.
Does Medicare pay for a nursing home?
Not for long-term custodial care. The skilled nursing facility benefit needs a qualifying three-day hospital stay, admission within 30 days, and it runs up to 100 days per benefit period with coinsurance from day 21.