What a 503A pharmacy is, why compounded costs less, and what FDA-approved means

Words you will hear

• 503A pharmacy: a traditional compounding pharmacy that makes drugs for individual patients under section 503A of the federal drug law.
• 503B outsourcing facility: a voluntary FDA category of larger compounder that can make batches. It follows factory rules and is inspected by the FDA.
• Compounded drug: a medicine a pharmacist or physician makes or changes for one patient. It is not an FDA-approved drug.
• CGMP (current good manufacturing practice): the FDA's factory rules for records, equipment testing, batch tracking and investigating failures.
• USP: the U.S. Pharmacopeia, a nonprofit that publishes quality standards for ingredients and for compounding.
• Bulk drug substance: the raw active ingredient, often a powder, before it is made into a finished medicine.
• Certificate of analysis: a document from the ingredient maker listing test results for a lot of ingredient.
• Essentially a copy: a legal test. A compounded drug that is essentially a copy of an approved drug is limited by law (see below).

What compounding is, and why the law allows it

Compounding means a pharmacist or physician makes or changes a medicine for one patient. The traditional uses are changes an approved product cannot offer, such as a liquid for someone who cannot swallow a pill, or a version without a dye the patient is allergic to. The FDA describes compounding as tailoring a medicine to an individual patient.

The main federal law for pharmacy compounding is section 503A of the Federal Food, Drug, and Cosmetic Act. Congress rewrote the compounding rules in 2013, after a 2012 contamination outbreak at a compounding pharmacy that killed at least 64 people. That rewrite also created the 503B outsourcing category.

Under the statute, simply mixing or reconstituting a drug exactly as its approved label directs is not counted as compounding.

What a 503A pharmacy has to do

The statute lists conditions a compounded drug must meet to use the 503A exemptions. In plain terms:

• Who: a licensed pharmacist in a state-licensed pharmacy, or a licensed physician, does the compounding.
• For whom: the drug is made for an identified patient, based on a prescription from a licensed prescriber. A limited quantity can be made ahead only when the pharmacy has a history of valid orders for that drug within an established relationship.
• Active ingredient: it must meet a U.S. Pharmacopeia monograph if one exists. If not, it must be a component of an FDA-approved drug or be on an FDA list of allowed substances. It must come from an FDA-registered establishment and have a certificate of analysis.
• Other ingredients: they must meet USP standards.
• Banned drugs: the pharmacy cannot compound a drug the FDA has withdrawn for safety or effectiveness reasons, or one on the FDA list of drugs that are hard to compound safely.
• No routine copies: the pharmacy cannot regularly, or in inordinate amounts, compound drugs that are essentially copies of a commercially available drug.
• Out-of-state limit: the statute limits how much a pharmacy can ship out of state (5 percent of its prescriptions) unless its state has an agreement with the FDA.

What a 503A drug is exempt from

A drug that meets those conditions is exempt from three things: FDA approval before sale, the CGMP factory rules, and the requirement for labeling with adequate directions for use. Other rules still apply, such as the ban on making drugs under insanitary conditions.

An industry group told TIME that 503A pharmacies must still follow USP guidelines and source active ingredients from FDA-registered suppliers. The pharmacies are overseen mainly by state boards of pharmacy, not by the FDA day to day.

503A versus 503B

This comparison follows a 2018 Congressional Research Service report and FDA pages. TIME reported in October 2026 that fewer than 100 outsourcing facilities exist. The Atlas did not check whether every detail is unchanged today.

The "essentially a copy" rule for GLP-1 drugs

The law says a 503A pharmacy cannot regularly, or in inordinate amounts, make drugs that are essentially copies of an approved drug. The exception is a change the prescriber decides makes a significant difference for that individual patient.

On April 1, 2026 the FDA said how it reads that rule for GLP-1 drugs. A compounded product is generally a copy if it has the same active ingredient in the same, similar or easily substituted strength, and the approved product can be given by the same route the prescriber ordered. The FDA's example is semaglutide plus vitamin B12: if each ingredient is within 10 percent of the approved product's strength, it would likely count as a copy. Unless the prescriber determines and documents a significant difference for the specific patient, the product is treated as a copy.

The FDA also said it does not currently intend to act against a pharmacy that fills four or fewer prescriptions of a copy product in a calendar month. That is a statement of enforcement policy, not a change in the law.

A law firm reported that on September 18, 2026 the FDA sent a warning letter to a compounding pharmacy over semaglutide and tirzepatide products with added ingredients such as vitamin B12 or niacinamide. In that account, the FDA said the products still looked like copies, that the volume suggested the claimed differences were a pretext, and that prescriptions lacked a documented prescriber determination or repeated identical wording. The Atlas has not read the letter itself.

In plain terms: adding a vitamin to a copy does not make it automatically allowed, and the record has to show a real reason that applies to that patient.

What FDA approval covers, and what compounded drugs skip

When the FDA reviews a new drug application, a team of physicians, chemists and statisticians examines the manufacturer's studies to judge whether the drug is safe and effective for its intended use. The FDA also reviews the label and inspects the factories where the drug will be made. The manufacturer must show the product on the market matches the one that was tested. After approval, the FDA keeps monitoring safety.

Compounded drugs generally skip that premarket review. The FDA says it does not verify their safety, effectiveness or quality before they are marketed.

Phrases that sound official but do not mean approved

• Made in an FDA-registered facility: registration applies to a business or an ingredient supplier. Approval applies to a specific drug and its application, which a compounded drug does not have.
• Made by a licensed 503A pharmacy: this refers to a state license. It does not mean the FDA reviewed the drug.
• Same active ingredient as Wegovy or Zepbound: the FDA says semaglutide sodium and semaglutide acetate are not the same active ingredient as in the approved drugs, and it is not aware of a lawful basis for compounding with them.
• Generic: a generic is a separate, FDA-approved copy of an approved drug. A compounded drug is not a generic.
• For research use only: the FDA advises against buying semaglutide, tirzepatide, retatrutide, survodutide and mazdutide sold this way for human use.

Why compounded versions cost less

No one tracks what compounding costs, so the Atlas can only report the reasons that sources and reporters give.

• High brand list prices: KFF Health News reported list prices of roughly $1,000 to $1,400 a month in 2024, and Stanford Medicine said in July 2026 that GLP-1 drugs at list price can exceed $1,000. Stanford also said generic semaglutide is not expected in the U.S. before 2032 at the earliest and that tirzepatide patents run to 2036.
• A low ingredient cost: KFF reported that compounders could buy semaglutide powder for under $4,000 a gram and estimated the ingredient at as little as about $10 per weekly dose before overhead. It said raw material prices had fallen about 35 percent as more makers entered the market.
• No application and no trials: compounded drugs skip the FDA's premarket review, so the compounder does not run trials or file an application. That removes costs a manufacturer has to recover. No source the Atlas read puts a number on that share.
• Cash pricing: insurers largely do not cover compounded drugs, so patients pay cash. TIME quoted a pharmacy attorney who said pharmacies often lose money on insured GLP-1 claims because of low reimbursement, which makes cash-pay compounding a significant revenue source.
• Different packaging: compounded doses are usually drawn from vials rather than delivered in branded pens, and KFF noted that some practices add markups.
• What patients reported paying: KFF put compounded semaglutide and tirzepatide at about $100 to $450 a month in 2024. TIME's October 2026 example was $250 a month for compounded tirzepatide mixed with vitamin B12, compared with $399 through the manufacturer's cash program for Zepbound.

The price gap has narrowed

In December 2025, trade press reported that Lilly's Zepbound single-dose vial cash prices ranged from $299 to $449 a month depending on the dose, and that Novo Nordisk's Wegovy cash price was $349 a month. Manufacturer cash prices change often, so check the current price with the manufacturer. The Atlas does not list current prices.

What a lower price does not mean

A lower price does not mean the same product. The Atlas found no trial that tested a compounded GLP-1 against the approved product, so the results in the approved labels cannot be assumed for a compounded version.

Reports differ on safety. A 2025 study cited by TIME found more reported side effects, and more prescribing and preparation errors, with compounded GLP-1 drugs than with brand-name versions between 2018 and 2024. The Alliance for Pharmacy Compounding says the claim that compounded drugs are less safe is subjective and cannot be proven. Some compounders say they test raw materials and finished products for potency, sterility and endotoxins. The FDA does not verify that testing before a compounded drug is sold.

Stanford clinicians pointed to specific differences: compounded products may use salt forms that have not been proven in people, may add ingredients such as vitamin B12 with no proven weight-loss benefit, and may come in vials with different concentrations, which raises the risk of dosing mistakes. The FDA has reported dosing errors of 10 to 20 times the intended amount.

Where the rules stand in 2026

• Shortages ended: the FDA says the tirzepatide shortage ended in late 2024 and the semaglutide shortage on February 21, 2025. That ended the main reason broad compounding was allowed.
• April 1, 2026: the FDA clarified how it applies the "essentially a copy" rule to GLP-1 drugs, as described above.
• April 30, 2026: the FDA announced a plan to leave semaglutide, tirzepatide and liraglutide off the 503B bulks list. A law firm described this as hitting outsourcing facilities hardest and as not directly changing the 503A framework, though it said 503A compounding of these drugs would likely need a documented, individualized medical need. That is the law firm's reading. The sources the Atlas read describe it as a proposal, not a final decision.
• September 18, 2026: the FDA warning letter described above.
• Peptides are a separate question. The FDA advisory committee votes of July 2026 concern other peptides, not semaglutide or tirzepatide. See the Peptide policy tracker and News.

Questions to ask

• Is the product you are giving me FDA-approved or compounded?
• If it is compounded, was it made by a 503A pharmacy or a 503B outsourcing facility, and what is the facility's name?
• Can I confirm that pharmacy's license with my state board of pharmacy?
• Why can I not use the approved product? What is the specific difference for me, and is it written in my record?
• Is the active ingredient the same form as in the approved drug, or a salt form?
• Does it contain anything added, such as a vitamin? What is it for, and what is the evidence?
• What strength and form will I get, and who will show me how to take it?
• What would the approved product cost with my insurance, and what is the manufacturer's cash price?

What is still unknown

• The Atlas found no trial that tested a compounded GLP-1 against the approved product.
• No source gave a full breakdown of what makes up a compounded price or a brand price, and prices change often.
• The 503A versus 503B comparison relies on a 2018 Congressional Research Service report. The Atlas did not verify current inspection practice or adverse event reporting for 503A pharmacies.
• The Atlas did not verify how the out-of-state shipping limit is applied today.
• The September 2026 warning letter is described from a law firm's account, and the April 2026 bulks list action is described as a proposal in the sources read. Check the FDA for the current status.
• State laws differ, and a state board of pharmacy may have its own rules.