Medicare Prescription Plan Rules and Limits
Your Medicare drug plan’s coverage rules determine which prescriptions are covered and how they are filled. In some cases, these rules may delay your prescription.
For Medicare Part D prescriptions, contact your drug plan to learn about its specific coverage rules.
For Medicare Part B prescriptions, such as many injectable or infused medications and certain vaccinations, contact your physician. These drugs are typically administered in a doctor’s office.
Why Your Pharmacy May Not Be Able to Fill a Prescription
There are several common reasons your health plan may prevent a prescription from being filled:
Your new plan is still processing
Step therapy requirements haven't been met
Quantity limit restrictions have been exceeded
A prior authorization or pre-certification is required
The plan's formulary has changed
You're using an out-of-network pharmacy
Your coverage has lapsed
To understand why your claim was denied, review the Explanation of Benefits (EOB) from your insurance carrier.
Key Prescription Coverage Terms
Formulary
A formulary, or drug list, includes the medications covered by your plan. If you have questions about whether a specific drug is on your plan's formulary, contact your insurance carrier.
Prior Authorization
Some prescriptions require approval before they can be filled. In these cases:
You or your prescriber must contact your plan.
Your prescriber may need to show that the medication is medically necessary.
Plans often require prior authorization for drugs covered only for certain medical conditions. Alternative covered medications may be listed on the plan's formulary.
Your insurance carrier can explain what’s needed to approve the prescription. The carrier's phone number is typically on the back of your insurance ID card.
If you can't fill a prescription because prior authorization or pre-certification is required, your physician may request an exception from the plan.
Step Therapy
Step therapy is a type of prior authorization. It requires you to try certain lower-cost, effective medications before moving to more expensive alternatives.
For example, a plan may require you to try:
a generic drug (if one exists), then
a lower-cost brand-name drug before covering a higher-cost brand-name option.
If your prescriber believes the higher-cost medication is medically necessary without first trying the others, you or your prescriber can request a step therapy exception from the plan.
Quantity Limits
For safety and cost reasons, plans may restrict how much of a drug can be dispensed over a certain period. For example, heartburn medications are often covered for one tablet per day for four weeks. Therefore, a plan may initially approve only a one‑month supply.
If your prescriber believes a higher quantity is medically appropriate, they can request a quantity limit exception from your plan.
In‑Network Pharmacies
The most cost‑effective way to fill your prescriptions is to use a preferred, in‑network pharmacy, whether retail or mail order. Standard in‑network pharmacies are also available, but your copay or coinsurance may be higher than at a preferred pharmacy. If you use an out‑of‑network pharmacy, you will need to pay the full retail price of the medication.
During your enrollment call, a Via Benefits licensed benefit advisor can help you identify which pharmacies are in network for the health plans you're considering.
If you’re already enrolled in a plan, contact your insurance carrier or visit its website to review the list of preferred and standard in‑network pharmacies (both retail and mail order). You can usually find the carrier’s phone number on the back of your insurance ID card.
Additional Assistance
For information about filling prescriptions by mail order, contact the carrier for your prescription drug plan. Their phone number is typically printed on the back of your insurance ID card.
If you’re having trouble reaching your carrier or need additional support, please contact us.
For assistance with shopping for a prescription drug plan on our website, read Shop and Enroll in Medicare Plans on the Website.