Medicare Part D: What It Covers, How It Works, and How to Save on Prescription Drugs

When you’re on Medicare, Medicare Part D, a federal program that helps cover the cost of prescription drugs for people enrolled in Medicare. Also known as Medicare prescription drug coverage, it’s not automatic—you have to pick a plan through a private insurer approved by Medicare. Without it, you could pay full price for medications like atorvastatin, lisinopril, or metformin, which can easily cost hundreds a month. Many people assume Part D is just about lowering pill costs, but it’s really about avoiding the coverage gap—the infamous "donut hole"—where you pay everything out of pocket until you hit a spending threshold.

What makes Part D tricky is that every plan is different. Some cover more generics, others include brand-name drugs like Cialis Extra Dosage or Entocort, but often with higher copays. The generic drugs, lower-cost versions of brand-name medications that contain the same active ingredients. Also known as generic medications, they make up 90% of prescriptions in the U.S. and are often the cheapest option under Part D plans. If you’re taking statins, blood pressure meds, or diabetes pills, choosing a plan that prioritizes generics can save you thousands a year. But you also need to check if your specific pharmacy is in-network. A plan that covers lisinopril might not let you fill it at the pharmacy you use every week.

Then there’s the issue of drug costs, the amount you pay for medications after insurance, including premiums, deductibles, copays, and out-of-pocket spending. Also known as out-of-pocket drug expenses, they can spike unexpectedly if your plan changes its formulary mid-year or if your drug gets moved to a higher tier. That’s why you should review your plan every year during Open Enrollment. A plan that was perfect last year might now charge more for your thyroid med or push you into the donut hole faster. And if you’re on multiple prescriptions—say, gemfibrozil for triglycerides and bupropion for depression—you’ll want to see how they interact under your plan’s tier system. Some plans even offer discounts for mail-order refills, which can cut costs further.

It’s not just about picking the cheapest plan. It’s about matching your meds to the plan’s formulary. If you’re using a specialty drug like ethionamide for drug-resistant TB or levonorgestrel IUD for contraception, make sure it’s covered at all—and at what cost. Many people don’t realize they can switch plans or even apply for Extra Help if their income is low. You don’t need a lawyer or a financial advisor to do it. The Medicare website lets you compare plans by drug list, pharmacy, and monthly cost in minutes.

Below, you’ll find real-world guides from people who’ve navigated these exact challenges: how to read pharmacy alerts when switching meds, how generic substitution works behind the counter, how to buy cheap lisinopril or Lasix safely online, and how to spot when an inactive ingredient might be causing side effects. These aren’t theoretical tips—they’re lessons from people managing daily prescriptions under Part D, trying to stay healthy without going broke.