A custom mix asks for a closer look.

Assumption to set aside · A familiar ingredient makes every version equivalent.

Ask which finished product is being proposed

Ask for the product name and its active ingredient: the substance that does the drug’s work.

FDA handles medicine approvals. It is short for Food and Drug Administration. In the approvals checked September 26, 2026, the semaglutide brands included Ozempic and Wegovy. Ozempic’s uses include controlling blood sugar in type 2 diabetes; Wegovy’s include helping people lose weight and keep it off. Tirzepatide has the brands Mounjaro and Zepbound. Mounjaro’s uses include treating type 2 diabetes; Zepbound’s include long-term weight control.

An approved medicine’s status does not carry over to a pharmacy’s custom mix, even when both use the same ingredient.

Compounding changes how the medicine is prepared

A compounder mixes a drug or changes how it is made. The result is a custom medicine, rather than the drug maker’s finished product.

FDA says a custom mix may fill a need that an approved drug cannot meet. It can also have a role when that drug is not on the market.

A person might need a dye left out because of an allergy, or a different form because swallowing a tablet is hard.

Under rules checked September 26, 2026, custom medicines are not FDA-approved, even with a prescription. FDA has not reviewed whether the custom mix works, is safe or meets quality standards before patients receive it.

Why does my care call for a custom preparation?

Ask why the law allows this particular custom mix

Federal rules limit the routine making of close copies of drugs already on the market. That is the position checked on September 26, 2026.

Your prescriber, the person writing the prescription, can identify a change that matters for your medical care. That must be a significant difference for you specifically; a cost saving is not enough.

An FDA national shortage listing can affect these copy rules. A pharmacy being out of stock does not establish a national shortage.

At the September 26, 2026 check, semaglutide injection and tirzepatide were absent from FDA’s shortage list.

If someone says they can make a copy because there used to be a shortage, ask why the rules allow your prescription now.

Adding a vitamin leaves a legal question

FDA says adding vitamin B12 to semaglutide can still leave a close copy. That was the agency’s position on September 26, 2026.

The prescriber must look at your own need. The added vitamin does not settle whether a mix meets the law.

Can we put my medical reason for this change in the record?

Do not accept a research-labelled product as treatment

The label “research use only” presents a product for laboratory work, rather than treating people. FDA urges people to avoid research-labelled drugs offered for treatment, in its account checked September 26, 2026. It warns that those products could harm people and that their quality has not been established.

In warning letters checked September 26, 2026, FDA said sellers broke federal law by shipping unapproved drugs across state lines. The sellers’ claims about treating people helped FDA reach that conclusion, despite their research labels.

Retatrutide appears in weight-loss offers, but it is not an ingredient in any FDA-approved medicine. Cagrilintide is another ingredient with no FDA-approved medicine. FDA’s position checked September 26, 2026 says federal law bars using either in custom-mixed medicines. For both ingredients, FDA says safety and benefit have yet to be established for any condition.