Three practical questions come up in the first month on GLP-1 medication, and all three have documented answers rather than folklore. Where the injection goes: the abdomen and thigh for both medicines, with the upper arm treated differently by each. How to store it: refrigerated before first use, with an after-first-use allowance that differs for every pen type. And what you can carry when travelling: Singapore permits up to three months' supply of your own prescribed medicine with documentation. One number in the current labelling is genuinely contradictory, and this article says so rather than picking a side.

Instructions for Use: the device leaflet packed with the pen itself, separate from the prescribing information. It is written for the exact presentation you were dispensed, which is why it beats any general article, including this one.

Where the labels say the injection goes

Both medicines are injected under the skin, and the site lists are close but not the same.

The US semaglutide label names the abdomen, thigh or upper arm, instructs at least 2 inches (5 cm) of clearance from the navel, and says sites are rotated with each dose — you may use the same body area each week, but not the same spot as the last injection (label).

Tirzepatide's US label diverges on one point that matters. It designates the thigh and stomach for self-injection, at least 2 inches from the navel, and states the back of the upper arm for administration by another person rather than for injecting yourself (label). Rotation is weekly.

So "upper arm" is not a class-wide instruction: one document has it as a self-injection site, the other as something a second person does. The leaflet in your own box is the reference, not a general guide.

Storage before first use

Both medicines are refrigerated at 2°C to 8°C (36°F to 46°F) before first use, and this is the one figure that is consistent everywhere (semaglutide, tirzepatide).

The semaglutide label adds that the pen is not stored in the freezer or directly against the refrigerator's cooling element (label). For the multi-dose tirzepatide presentation there is an additional route: unopened, it can be kept refrigerated until the printed expiry date, or at room temperature up to 30°C (86°F) for 30 days before opening (label).

After first use, the day-limit depends on which pen

This is the part most often got wrong, because people repeat a number from a different pen.

Four presentations, four different figures in the US labelling:

  • Single-dose semaglutide pen or syringe — may be kept from 8°C to 30°C (46°F to 86°F) for up to 28 days, and is thrown away if it has been frozen, exposed to light or to temperatures above 30°C (86°F), or out of the refrigerator for 28 days or longer (label).
  • Multi-dose semaglutide pen — 56 days after first use, with the same "discard if exposed above 30°C (86°F)" trigger (label).
  • Single-dose tirzepatide pen or vial — may be kept unrefrigerated at temperatures not to exceed 30°C (86°F) for up to a total of 21 days, then discarded even if medicine remains (label).
  • Multi-dose tirzepatide vial or pen — discarded at whichever comes first of 30 days at room temperature, 30 days after first use, or the fourth weekly dose, again even with medicine left in it (label).

Note also that the tirzepatide phrasing is a ceiling — "not to exceed 30°C" — while the single-dose semaglutide phrasing is a two-sided range, 8°C to 30°C. One does not convert into the other.

The room-temperature figure the label contradicts itself on

For the multi-dose semaglutide pen, the current US label states two different after-first-use room-temperature ranges in two different places within the same document (label).

The 56-day duration is stated consistently, and so is the instruction to discard the pen if it has been above 30°C (86°F). The temperature band for ordinary day-to-day storage is where the document disagrees with itself, and that has not been resolved.

So this article gives no number for it. Read the leaflet that came with your own pen and put the question to your pharmacist, who can look at the exact presentation in front of you. Where a document contradicts itself, the answer belongs to a person with your pen in view.

Travelling: what Singapore allows you to bring

The Health Sciences Authority sets a general rule for personal medication: up to three months' supply where no approval is needed and the medicine is not prohibited, carrying a copy of a valid prescription or doctor's letter, with each medication in its original container or packaging and labelled by the dispensing pharmacy with the patient name, medication name and quantity (HSA).

Two things follow. The allowance is for your own prescribed medicine, not for carrying supply for someone else. And the "original packaging" requirement is about authenticity — decanting pens into an unlabelled cool bag defeats the documentation, whatever it does for temperature.

On temperature itself, there is a gap worth naming. That page covers quantity, documentation and labelling, and carries nothing about cold-chain storage, refrigeration, insulated carriers or ice packs (HSA). No Singapore government source located tells a traveller how to keep a pen cold. Ask your pharmacist, and read the storage section of your own leaflet before you pack.

Getting through the airport

Changi Airport lists medication accompanied by a doctor's letter among the exceptions to its powder-screening rule, and states that items may be exempted from the 100ml cap on liquids, aerosols and gels on presentation of a bona fide doctor's letter (Changi Airport). Cooling packs are not named anywhere on that page, so the letter is the thing doing the work — expect to explain what you are carrying.

Singapore Airlines is more specific about needles: a prescription or note from a registered physician is required to carry syringes or hypodermic needles on board, and medically necessary ones are exempt from the usual prohibitions where the passenger also has the prescription medication with a professionally printed label identifying the medical office, pharmacy or manufacturer. Medication is permitted in cabin baggage within a reasonable amount, with a physician's letter recommended (Singapore Airlines).

Other carriers set their own policies, so check the one you are flying. And if a trip runs longer than the after-first-use window for your pen, that is a scheduling question for your prescriber before you leave rather than an improvisation at the destination. We cover the related timing problem in what to do about a missed dose.

Individual circumstances vary. Nothing here replaces the Instructions for Use supplied with your medicine or the direction of the doctor who prescribed it.

Two questions this page does not answer sit alongside it. The shape of a first dose is in your first GLP-1 injection, and what to do when something seems to have gone wrong is in if you think you injected it wrong.

Common questions

Where do you inject GLP-1 medication?

The US semaglutide label names the abdomen, thigh and upper arm, with at least 2 inches (5 cm) clearance from the navel and rotation within the chosen area (label). Tirzepatide's differs: abdomen and thigh for self-injection, with the back of the upper arm stated for someone else to administer (label). Follow the leaflet packed with your own pen.

How long can a GLP-1 pen stay out of the fridge?

It depends entirely on which pen. The US labels give 28 days for the single-dose semaglutide pen (label), 56 days for the multi-dose semaglutide pen (label), 21 days for the single-dose tirzepatide pen or vial (label) and 30 days for the multi-dose tirzepatide presentation (label). These are not interchangeable.

What room temperature should the pen be kept at?

For the multi-dose semaglutide pen, the current US label states two different ranges in two different sections, and that inconsistency is unresolved (label). Follow the leaflet supplied with your own pen and ask your pharmacist to confirm it. Do not take a number from an article, including this one.

Can you fly with GLP-1 medication to or from Singapore?

Singapore's rule for bringing in your own prescribed medicine is up to three months' supply where no approval is needed, with a copy of a valid prescription or doctor's letter, in the original packaging labelled by the dispensing pharmacy with your name, the medication name and the quantity (HSA).

Do you need a doctor's letter to carry an injection pen on board?

Singapore Airlines states that a prescription or note from a registered physician is required to carry syringes or hypodermic needles on board (Singapore Airlines), and Changi lists medication accompanied by a doctor's letter among its screening exemptions (Changi Airport). Check your own airline as well.