Who should not take GLP-1 medication?

The list of people who formally cannot take GLP-1 medication is shorter than most people expect — and it is not the same list in Singapore as in the United States. Singapore's registered product information lists one contraindication: hypersensitivity to the medicine or its ingredients. The US prescribing information adds a second: a personal or family history of medullary thyroid carcinoma or MEN 2. Beyond those formal lists sits a much larger set of things a doctor weighs. This article explains both, and why the difference matters for anyone reading American health sites from Singapore.

Contraindication: a formal instruction that a medicine must not be used in a defined situation. Distinct from a warning or precaution, which flags a risk requiring judgement rather than an automatic no.

The formal contraindications

In Singapore. The product information for the registered semaglutide and tirzepatide products lists a single section 4.3 contraindication: "Hypersensitivity to the active substance or to any of the excipients" (National Drug Formulary). That matches the European structure.

In the United States. The prescribing information for both medicines contraindicates them in patients with "a personal or family history of MTC or in patients with MEN 2", alongside prior serious hypersensitivity (semaglutide, tirzepatide).

That difference is real, and it is worth understanding rather than glossing. It does not mean the thyroid question is irrelevant here. It means the two regulators structured their documents differently — and that a Singapore patient reading a US site is reading a document that does not govern their prescription.

Two practical points follow. Anyone with a personal or family history of medullary thyroid carcinoma or MEN 2 should raise it, and expect a careful conversation. And nobody should read the absence of that item from Singapore's section 4.3 as clearance — Singapore's warnings-and-precautions section is not published publicly, so what it says about the thyroid signal is genuinely not something we can see.

The thyroid warning, in proportion

The reason MTC appears at all is a rodent finding.

In mice and rats, semaglutide caused dose-dependent and duration-dependent thyroid C-cell tumours at clinically relevant exposures; for tirzepatide the same was seen in a two-year rat study. The prescribing information for both states, in its own words, that it is unknown whether the medicine causes thyroid C-cell tumours in humans, "as human relevance of… rodent thyroid C-cell tumors has not been determined" (semaglutide, tirzepatide).

So the evidence base here is animal work, and the regulators have said explicitly that they do not know whether it carries over. That is a reason for the specific exclusion of people already at genetically elevated risk, and it is not a reason for general alarm. The same document that carries the warning is the document that says the human relevance is undetermined.

What is a warning rather than a contraindication

Most of what people worry about falls into this category — a flagged risk requiring judgement, not an automatic exclusion.

Acute pancreatitis is listed as a warning and precaution rather than a contraindication (prescribing information). In the US labels the same section also covers gallbladder disease, acute kidney injury from fluid loss, severe gastrointestinal reactions, hypoglycaemia when combined with insulin or a sulfonylurea, and diabetic retinopathy complications in people with type 2 diabetes. Semaglutide's US label additionally carries a heart-rate precaution with a monitoring instruction; tirzepatide's records heart rate as an adverse-reaction observation without one. Singapore's equivalent section is not published publicly, so we describe the US document and say so.

A history of any of these does not settle the question by itself. It changes the conversation, and in some cases it means further checks before starting rather than not starting at all.

Pregnancy, breastfeeding and planning a family

This one has a specific timing element that catches people out.

The product information instructs discontinuing when pregnancy is recognised. For semaglutide, both the US and European documents go further and instruct stopping at least two months before a planned pregnancy, because the medicine has a long half-life. For tirzepatide the European document gives one month, and the current US document gives no pre-conception window at all (pregnancy and lactation sections).

The practical version: if you are planning a pregnancy in the next year, that belongs in the conversation at your first consultation, not later. The washout is measured in months, not days.

What a doctor actually screens for

The formal lists are the floor, not the assessment. A doctor is working through considerably more than a contraindication checklist: your medical history, the medicines and supplements you take, relevant surgical history, thyroid and endocrine history including family history, pregnancy and family planning, and how your eating actually works.

Some of that is looking for exclusions. Much of it is looking for things that change the plan — a starting dose, a monitoring interval, a check to do first. What exactly is reviewed, and whether any tests are involved, is a question for the clinic treating you.

At GetLean, our philosophy is that the medication is the catalyst, and the assessment is where it is decided whether that catalyst is the right one for a particular person. If the doctor wants more information before prescribing, that is not a rejection. It usually means some further checks are worth doing so treatment can start safely.

These medicines are Prescription Only in Singapore (HSA register), which is exactly why none of this can be settled by a form or an article. Individual circumstances vary, and the decision belongs to a doctor registered with the Singapore Medical Council who has assessed you.

One thing that is emphatically not on this list is being frightened of needles. Afraid of needles covers how common that is, what has been tried, and why it is a clinical conversation rather than a disqualification.

Common questions

Who cannot take GLP-1 medication?

Singapore's registered product information gives one formal contraindication: hypersensitivity to the medicine or its excipients (NDF). The US prescribing information adds a personal or family history of medullary thyroid carcinoma or MEN 2 (prescribing information). A doctor screens for both and for a considerably wider set of factors.

Can you take GLP-1 medication if thyroid cancer runs in your family?

That history is exactly what a doctor needs before prescribing. The US prescribing information treats a personal or family history of medullary thyroid carcinoma or MEN 2 as a contraindication (prescribing information); the underlying evidence is a rodent finding whose human relevance the same document says has not been determined. Tell your doctor rather than deciding from an article.

Can you take GLP-1 medication while pregnant or trying to conceive?

No. The product information instructs stopping when pregnancy is recognised, and for semaglutide both the US and European documents instruct stopping at least two months before a planned pregnancy because of the long half-life; the European document gives one month for tirzepatide (pregnancy sections). Raise family planning at your first consultation.

Does a history of pancreatitis rule you out?

Not automatically. Acute pancreatitis is a listed warning rather than a contraindication (prescribing information), meaning it calls for clinical judgement rather than an automatic exclusion.

Who decides whether it is safe for me?

A doctor registered with the Singapore Medical Council, after a proper assessment. These medicines are Prescription Only in Singapore (HSA register).