Part D Coverage: What It Includes and How It Affects Your Medication Costs

When you’re on Part D coverage, the Medicare prescription drug benefit that helps pay for medications. Also known as Medicare drug coverage, it’s designed to make essential pills more affordable for seniors and people with disabilities enrolled in Medicare. Without it, many people pay full price for drugs like insulin, blood pressure meds, or cholesterol-lowering statins — costs that can easily hit hundreds of dollars a month.

Part D coverage isn’t one single plan. It’s offered through private companies approved by Medicare, and each plan has its own list of covered drugs — called a formulary. Some plans cover brand-name drugs first, others push generics. Some have low monthly premiums but high out-of-pocket costs after you hit the deductible. Others cover more of your costs early on but charge more each month. The Part D coverage you pick can mean the difference between taking your meds as prescribed or skipping doses because you can’t afford them.

Not all drugs are covered the same. Many plans use tiered pricing: Tier 1 might be generic drugs costing $5, while Tier 4 or 5 could be specialty meds like those for HIV or autoimmune diseases, costing $500 or more. If you’re on a drug like isoniazid for tuberculosis or atorvastatin with cobicistat for HIV, your plan might require prior authorization, a process where your doctor must prove the drug is medically necessary before the plan pays. Some plans also use step therapy, a rule that forces you to try cheaper alternatives first — even if your doctor says they won’t work for you. And if you’re on a drug that interacts with grapefruit juice or caffeine, your plan won’t warn you — that’s on you to know.

Part D also has a coverage gap — the infamous "donut hole." Once you and your plan spend a certain amount on drugs, you pay more out of pocket until you hit the catastrophic coverage threshold. In 2025, you’ll pay no more than 25% of the cost for both brand-name and generic drugs in the gap, but that still adds up fast if you’re on multiple high-cost meds. That’s why checking your plan’s formulary every year matters. A drug you took last year might be moved to a higher tier, or a cheaper generic might now be available.

People often think Part D covers everything — but it doesn’t. It doesn’t cover over-the-counter meds, most vitamins (unless they’re part of a specific treatment like AREDS2 for macular degeneration), or drugs used for weight loss or cosmetic purposes. And if you’re buying meds from an online pharmacy, make sure it’s licensed. FDA oversight, the system that ensures drugs sold in the U.S. are safe and effective doesn’t extend to every website claiming to be a "Canadian pharmacy." Counterfeit pills with fentanyl or toxic contaminants are a real risk, and your Part D plan won’t pay for them.

What you’ll find here are real, practical stories from people navigating Part D coverage — how pharmacists fight for prior authorizations, why some generic drugs cost ten times more overseas, how drug interactions with food or supplements can sabotage your treatment, and what to do when your meds aren’t covered. Whether you’re managing diabetes with insulin, controlling cholesterol with statins, or dealing with side effects like hair loss or hot flashes from your prescriptions, the articles below show you how to make Part D work for you — not against you.