Taking Mounjaro Home From Japan: Singapore and US Rules

Getting Mounjaro prescribed in Tokyo is the easy part. The question people actually worry about is the flight home — whether it will be taken off them at the border, and what they are supposed to show. This page covers the rules for Singapore and the United States, and the general principles that apply wherever you are going.

The three things that matter everywhere

Border rules differ in their detail, but the same three things decide how the conversation goes.

1. Is it obviously yours, and obviously medicine? Original box, pharmacy label with your name on it, quantity visible.
2. Can you show it was prescribed? A prescription, a doctor’s letter, or a prescription certificate — in English.
3. Is the quantity sensible for one person? Personal-use amounts pass easily. Large quantities invite questions everywhere.

And one rule about the flight itself: keep the pens in your hand luggage. The cargo hold can get cold enough to freeze them, and a frozen pen has to be thrown away.

Singapore

Singapore’s Health Sciences Authority (HSA) publishes clear limits for personal medication brought in by travellers.

You may bring up to 3 months’ supply if no approval is needed and the medication is not prohibited.

Alongside the quantity, HSA asks you to “provide pharmacy dispensing labels, doctor’s prescription, or doctor’s letter”, and states that “each medication should be in their original container/packaging and also labelled with the patient name, medication name and quantity”.

Two further points:

• Medicines containing controlled substances need approval in advance. Tirzepatide is a prescription-only medicine in Singapore rather than a controlled drug, but if you are carrying anything else, check HSA’s list.
• Where an approval is needed, HSA asks you to “submit your application at least 2 weeks before your arrival in Singapore”.

The current guidance is on the HSA page Travelling with medications to Singapore.

United States

US Customs and Border Protection (CBP) asks travellers to declare all medicines and similar products on arrival. Beyond that, the guidance is about documentation and quantity:

• Original containers with the prescription printed on them. If the medicine is not in its original container, carry a copy of the prescription or a letter from your doctor.
• Personal-use quantities only. CBP gives a rule of thumb of no more than a 90-day supply.
• Only medicines that can legally be prescribed in the United States may be imported for personal use. Tirzepatide is approved and prescribed in the US, so it meets that test.

For the flight, the Transportation Security Administration (TSA) treats injectable medicines, needles and medically necessary gel ice packs as permitted in carry-on baggage. They are exempt from the usual liquid limits when carried in reasonable quantities and declared for separate screening, so take them out of your bag and tell the officer before screening starts.

Current guidance: CBP — Traveling with Medication to the United States and TSA — Medications (liquid).

One honest caveat. The decision at the border always rests with the officer on duty. Documentation and sensible quantities make the process straightforward; they are not a guarantee, and no clinic can give you one.

Somewhere else?

The pattern above — a personal-use quantity limit, a documentation requirement, and a separate régime for controlled substances — is close to universal, but the numbers are not. Check with your own country’s medicines regulator or customs authority before you travel, particularly if you are carrying more than a couple of months’ supply.

If you are also bringing medicine into Japan, that has its own separate rules, which we cover in Can you bring Mounjaro into Japan?

The English prescription certificate

Every rule above turns on being able to show that the medicine was prescribed to you. If you were prescribed in Japan, your paperwork will be in Japanese, which is not much use at a border in Changi or Los Angeles.

We can issue an English prescription certificate for JPY 3,000 (≈ USD 19). Ask for it when you book or at the appointment, and have your home address in English ready, because it goes on the document. It is a supporting document rather than a guarantee of entry — but it is the document every officer is actually asking for.

US dollar figure is approximate, at USD 1 ≈ JPY 159 (24 August 2026).

Keeping it cold on the way home

Mounjaro is normally kept refrigerated at 2–8°C, and may be kept below 30°C for up to 21 days in total. A long-haul flight therefore does not put the medicine at risk on its own — put the pens back in a fridge when you get home, and remember that the 21 days is cumulative, not per trip.

If you would rather not think about it, an insulated cooler bag is the simple answer. We keep them in stock for travellers.

FAQ

Do I have to declare it, or only if I am asked?

For the United States, declare it — CBP asks travellers to declare all medicines. Elsewhere, follow the arrival card and the signage, and answer honestly if asked. Declaring costs you nothing; not declaring is what causes problems.

Can I put the pens in my checked suitcase if my carry-on is full?

Please do not. This is not a customs rule but a practical one: the hold can drop below freezing, and frozen tirzepatide must be discarded. Checked baggage also gets lost, and a lost bag is a lost month of treatment.

How much can I actually take home?

Singapore publishes a limit of 3 months’ supply without approval. CBP gives a rule of thumb of 90 days. Both are about what one person would reasonably use, judged against the dose on your label — so keep the label.

Will the needles be a problem at security?

No, when they are carried with the medicine they belong to. TSA permits needles and syringes in carry-on baggage alongside the injectable medicine. Declare them with the medicine at the checkpoint.

Can you post it to me after I get home?

No. Repeat prescriptions can be delivered to an address within Japan, or collected at the clinic on a later trip. Sending prescription medicines across borders by post is treated as importing rather than as personal luggage, and is governed by the receiving country’s import rules.

This article is general information, not medical or legal advice. Customs and aviation rules change and are applied at the discretion of the authorities concerned. Please confirm the current requirements with the relevant authority before you travel.

Related reading

• Where to get Mounjaro in Tokyo as a visitor — what to bring, and what it costs.
• Mounjaro, Zepbound, Wegovy and Ozempic in Japan — what each brand is actually approved for here.
• Can you bring Mounjaro into Japan? — the one-month rule and the Yakkan Shoumei.