Blog / Part D

What is prior authorization and step therapy for my medication?

Prior authorization means the plan must approve a drug before it pays. Step therapy means trying a lower cost drug first. Both can be appealed and show in Plan Finder.

Updated September 3, 2026 · 3 min read · by Gerino Alejos

Prior authorization means your plan must approve a drug before it will pay for it. Step therapy means the plan wants you to try a lower cost drug first. Both can hold up a drug that is on your plan's formulary, its list of covered drugs, and neither one is a final no.

Prior authorization

The plan requires approval before it covers the drug. Your doctor sends in medical information showing why you need it.

Plans have deadlines to answer. A standard request gets a decision within a set number of days. An expedited request, used when waiting could seriously harm your health, is much faster.

Most requests are approved. The cost is the delay and the paperwork, which falls on your doctor's staff and on you.

Step therapy

The plan requires you to try a lower cost drug first. Only if that drug does not work well enough will the plan cover the one your doctor first prescribed.

This is the rule to watch if you are already stable on a medication. Being told to switch to something else and fail on it, when you are doing fine, is a real disruption. It is usually avoidable. Your doctor files an exception request showing that you already tried the alternatives.

Quantity limits

A quantity limit is a cap on how much of a drug the plan covers per fill or per period. It is usually based on the maker's recommended dose. If your prescription is for more than that, your doctor asks for an exception and explains the medical reason.

How to get a restricted drug approved

1. Ask the pharmacy exactly which restriction applies. They can see it in their system.
2. Call your doctor's office and tell them which restriction and which plan. Most offices handle these all the time.
3. Ask for an expedited request if waiting would harm you.
4. If you already tried the step therapy drug and it failed, say so and give the history. That usually settles it.
5. If the plan says no, appeal. There are several levels, and denials get overturned fairly often.

The transition supply

When you join a new plan, or a plan's formulary changes in January, the plan must usually give you a temporary supply of a drug you were already taking. That is usually a one month fill within the first 90 days.

It exists so you are not left without medication while an approval is sorted out. Use it, and start the approval right away instead of waiting until the temporary supply runs out.

Check for restrictions before you enroll

The Plan Finder at Medicare.gov flags prior authorization, step therapy and quantity limits for each drug on each plan.

A plan that looks lowest in price on paper, but puts step therapy on a drug you are stable on, will not be the lowest in practice. Check the flags, not just the totals. See how to compare plans properly.

Advantage plans use it on the medical side too

Prior authorization is not only for drugs. Medicare Advantage plans often require it for imaging, for skilled nursing stays, which is nursing care in a facility after a hospital stay, and for some procedures. If you are choosing a plan, it is fair to ask how much it uses prior authorization and how fast it usually decides.

See the downsides of Advantage plans. If a drug is stuck at the counter today, ask the pharmacy which restriction applies and call your doctor's office. If you want help with the paperwork, call our McAllen office or send us your ZIP code through the form on this page.

Gerino Alejos

Licensed insurance agent · License 3128710 · NPN 18243381

Owner of McAllen Insurance Group, an independent agency on North 10th Street in McAllen. Works with clients across Hidalgo, Cameron and Starr counties on Medicare, Marketplace health, life and auto coverage. Se habla español.