Generics, brand names and biosimilars: what's the difference?

Three kinds of medicine on the shelf

When a drug company invents a new medicine, it sells it under a brand name. Once patents and other protections run out, other companies can ask the Food and Drug Administration (FDA) for permission to sell their own versions. For ordinary pills and many other medicines, those copies are called generics. For biologics, which are complex medicines made from living cells, the copies are called biosimilars.

Knowing the difference can help you understand why your pill suddenly looks different, why your pharmacist offers a substitute, and why your bill may drop.

What a generic drug is

According to the FDA, a generic drug contains the same active ingredient as the brand-name drug and must work the same way in the body. It must also have the same strength, the same dosage form (for example, a tablet or a capsule) and the same route of administration (for example, swallowed or injected).

Before approving a generic, the FDA requires the company to show that it is bioequivalent to the brand. That means it delivers the same amount of active ingredient into the bloodstream, at a similar rate and to a similar extent.

Generic makers do not have to repeat the large, expensive clinical trials the brand company ran. Instead, they show their product is equivalent to a drug the FDA already found safe and effective. That is a big reason generics usually cost less.

Why your generic may look different

The FDA generally allows minor differences in appearance between a generic and its brand, such as color or shape. These differences do not change how the medicine works.

Inactive ingredients, such as fillers and dyes, can also differ. The FDA says that in most cases this does not matter, but in a minority of patients inactive ingredients may affect how well a medicine is tolerated or absorbed. If you have an allergy to a dye or other ingredient, or you notice a change after a refill switches manufacturers, tell your pharmacist or doctor.

Quality rules are the same for all of them. The FDA says every batch of medicine sold in the U.S. must meet the same quality standards, no matter where it is made, and the agency inspects manufacturing plants around the world.

What a biosimilar is

Biologics include many injected and infused medicines, such as some treatments for arthritis, cancer, diabetes and eye disease. Because they are made in living systems, an exact copy is not possible. A biosimilar is a highly similar version of an FDA-approved biologic, which is called the reference product.

To be approved, a biosimilar must have no clinically meaningful differences from its reference product in safety, purity or potency. The FDA says biosimilars are as safe and effective as the reference product, and that its own research found no difference in the risk of death, serious side effects or stopping treatment when patients switched between them.

What "interchangeable" means

Some biosimilars are also approved as interchangeable biosimilars. A company has to ask for this designation and meet additional requirements.

The practical difference shows up at the pharmacy. An interchangeable biosimilar may be substituted for the reference product by a pharmacist without a new prescription, depending on state pharmacy laws. Other biosimilars generally must be prescribed by name. Rules on substitution, and on notifying your doctor, vary from state to state.

The FDA has said it is updating its guidance to recommend fewer tests to show interchangeability. As of late October 2026, that guidance was still in draft form, so the rules may change.

How much you might save

The FDA says generic drugs can cost as much as 80% to 85% less than their brand-name versions. Your actual savings depend on your insurance plan, your pharmacy and how many companies make the generic.

For biosimilars, the FDA says they may cost less than the reference product and add treatment options. It also stresses that a lower price is not a sign of lower quality or safety. Whether a biosimilar saves you money depends a lot on how your plan covers it, so check your plan's drug list, also called a formulary.

Questions to ask your doctor or pharmacist

Generics and biosimilars are not the right choice for every person in every situation. Talk with your doctor or pharmacist about your own medicines. Useful questions include:

• Is there a generic or biosimilar version of this medicine, and would it work for me?
• Is the biosimilar interchangeable, and can the pharmacy switch it without a new prescription in my state?
• Will my out-of-pocket cost be lower with the generic or biosimilar under my plan?
• Does the generic have any inactive ingredients I should avoid because of allergies?
• If my pill looks different after a refill, is it the same medicine from a different maker?
• Is there a cheaper brand-name drug in the same class, if no generic exists yet?

Where to look things up

The FDA keeps a searchable database of approved biological products, called the Purple Book, that shows which biosimilars are approved and which are interchangeable. Your pharmacist can also look up whether a generic is rated as equivalent to your brand. This article is general information, not medical advice. Do not stop or switch a medicine on your own; ask your doctor or pharmacist first.