You can drop a Medicare Advantage plan and go back to Original Medicare during specific windows each year, not whenever you decide you want to. The two main opportunities are the Annual Enrollment Period, which runs from October 15 to December 7, and the Medicare Advantage Open Enrollment Period, which runs from January 1 to March 31. During the fall Annual Enrollment Period you can switch from Medicare Advantage back to Original Medicare, with or without a Part D drug plan, and the change takes effect January 1. During the Medicare Advantage Open Enrollment Period, if you are already in an Advantage plan, you get one chance to switch to Original Medicare and add a standalone Part D plan, with the change taking effect the first day of the month after you make the switch.
Outside of those windows, you generally cannot switch unless you qualify for a Special Enrollment Period, which can happen if you move out of your plan's service area, your plan leaves Medicare, you qualify for both Medicare and Medicaid, or a few other specific life events.
The part that trips people up is not the switch itself but what happens to supplemental coverage. Original Medicare does not cap your out-of-pocket costs, so most people pair it with a Medigap (Medicare Supplement) policy to cover deductibles, coinsurance, and extra expenses. When you first enroll in Medicare, you have a six-month Medigap open enrollment window during which insurers must sell you a policy regardless of health problems. If you used that window to go straight into a Medicare Advantage plan instead, and now want to return to Original Medicare later, you may not have automatic guaranteed-issue rights to a Medigap policy. Insurers in most states can then medically underwrite you, charge more, or deny coverage based on health conditions.
There are some exceptions. If you are in your first year of Medicare Advantage as a trial and decide to switch back within that 12-month trial period, federal law guarantees you the right to buy a Medigap policy without medical underwriting. A handful of states also have their own rules that offer broader guaranteed-issue protections for people switching plans at other times, so it is worth checking your state insurance department's rules before assuming you will be denied.
Before switching, compare your total costs carefully. Original Medicare plus a Part D drug plan and a Medigap policy often costs more in monthly premiums than a Medicare Advantage plan, but it usually offers more predictable costs and broader provider access, since Medicare Advantage plans typically use networks while Original Medicare is accepted by any provider that takes Medicare nationwide. If network access, specific specialists, or traveling frequently matter to you, that may tip the decision toward Original Medicare despite the premium difference.
If you decide to switch, contact 1-800-MEDICARE or your State Health Insurance Assistance Program (SHIP) for free, unbiased help comparing Medigap options and confirming whether you have guaranteed-issue rights in your situation before you cancel your Medicare Advantage plan.