Skip to the note

Term / Boxed warning

Boxed warning: the caution to read before deciding.

A boxed warning is the strongest caution the Food and Drug Administration (FDA) uses in official medicine instructions.

Get urgent help for severe allergy signs

The National Library of Medicine lists these signs of a severe allergic reaction: trouble with breathing, trouble with swallowing, and a swollen face or tongue.

For severe signs of an allergic reaction, call 911 or go to the nearest emergency room.

Source: severe allergic reactions

Bring these topics to the care visit

The health professional writing a prescription is called a prescriber.

Bring diagnosis names and any records from past hospital care or surgery. Ask the prescriber to help check them.

  • Cancer in you or your family, especially the rare cancer named medullary thyroid cancer.
  • A family diagnosis named MEN 2. This rare condition can pass from a parent to a child. Ask for help checking family records for this name.
  • Past belly problems, especially gallstones, painful swelling or severe stomach trouble, or an operation for those problems.
  • Diabetes medicines and eye problems from diabetes.
  • Pregnancy plans, birth control pills and planned surgery.

What the boxed warning says

Rat findings and the rules for use

Both medicines’ official instructions report tumours, meaning growths, in rats. These were in the body part affected by the rare cancer named above. It is unknown whether this happens in people.

The instructions prohibit tirzepatide use when either you or someone in your family has a history of the rare cancer called medullary thyroid cancer.

They also rule it out if you have MEN 2, the condition passed through families, or a past serious allergy to tirzepatide or its other ingredients.

Stomach problems are common; some problems are serious

What the weight-loss studies found

In the Zepbound (tirzepatide) weight-loss studies, 25–29% of people taking it felt sick, compared with 8% on a dummy shot.

A dummy shot has no active study medicine.

Loose stools, vomiting and constipation were also common.

The official instructions warn that losing too much fluid after stomach side effects can damage the kidneys, and advise against use with severe gastroparesis, meaning the stomach empties very slowly.

The instructions also report serious painful swelling inside the belly, called pancreatitis, and serious allergic reactions.

Signs of pancreatitis include belly pain that lasts or is severe, sometimes spreading to the back.

Problems such as gallstones, painful swelling or an operation to remove the affected body part were also more common with tirzepatide. The instructions group these as gallbladder disease.

Ask the prescriber which symptoms need a quick call and which need emergency care.

The pill, pregnancy and surgery need a discussion

These are official medicine instructions

The official Zepbound instructions tell prescribers to advise a form of birth control other than a pill, or to add a backup method. This advice applies for 4 weeks when treatment starts and for the same length of time after every increase in medicine strength.

Those instructions also tell prescribers to stop Zepbound when pregnancy is found.

The official instructions warn of a risk during anesthesia: what is in the stomach may get into the lungs. Anesthesia means medicines that keep a person unconscious for surgery.

Tell the surgical team about tirzepatide and ask them for a plan.

Claims that make an offer suspect

Check these before paying

As of September 26, 2026, supplying a prescription medicine in the US requires a valid prescription first.

Some tirzepatide products are sold for people to use while marked “for research purposes” (for studies) or “not for human consumption” (not for people to use).

The FDA warns against buying those products because their quality is not known and they could cause harm.

Claims that a compounded drug has FDA approval or is proven to match an approved product are misleading.

Next term: Study average