The GLP-1 family: differences between the molecules

One name covering several different molecules

"GLP‑1" is used as though it described a single drug. It describes a hormone, and a family of medicines that act on its receptor — and they differ from each other in ways that matter clinically.

This page explains those differences. It is not a comparison of what you should take, and nothing here is a recommendation.

The molecules

• Liraglutide — a GLP‑1 receptor agonist, injected daily. The older of the ones in common use.
• Semaglutide — a GLP‑1 receptor agonist, injected weekly. Also exists as an oral tablet taken daily, which has specific and strict dosing instructions around food and water.
• Dulaglutide — a GLP‑1 receptor agonist, weekly.
• Tirzepatide — not a GLP‑1 agonist alone. It acts on two receptors, GLP‑1 and GIP, which makes it a different class of molecule despite being grouped with the others.
• Exenatide — an earlier agent, less used now.

In Costa Rica, several of these hold sanitary registration and are sold through ordinary pharmacies. Which specific brands and presentations are available changes, and the registry rather than a clinic's website is the place to check.

The single most important distinction

The same molecule is registered under different brand names for different conditions, at different doses.

Semaglutide is the clearest example: it is registered for type 2 diabetes under one brand and for weight management under another, at a higher dose. They are the same active ingredient. They are not interchangeable prescriptions, they are priced differently, and which one is appropriate is a clinical and regulatory question rather than a shopping one.

This is the reason the Ministry of Health's October 2025 warning requires that a patient be told the brand, the active ingredient and the registration number. Those three facts distinguish a registered medicine prescribed properly from everything else, and they are the three a patient can ask for in any consultation.

Where the real differences lie

• Dosing frequency. Daily versus weekly, which matters more to adherence than most people predict.
• Route. Injection for most; one oral option, with demanding instructions.
• Mechanism. Single receptor versus dual. Head‑to‑head trials have reported differences in average weight change between agents, with the dual‑receptor agent performing strongly — but trial averages describe groups, and individual response varies widely.
• What each is registered for. Some have additional approved indications based on cardiovascular outcome trials. An approved indication is a regulatory fact, not a marketing claim, and it is checkable.
• Titration. All are started low and increased in steps, over weeks. The schedule differs between agents and exists to limit side effects.

What does not differ

All of them require a prescription after an individual medical assessment. All require a cold chain — they are temperature‑sensitive biological products, and one that has been warm is not safe to use. All carry contraindications, including a personal or family history of medullary thyroid carcinoma or MEN2 for several of them. All share a broadly similar side effect profile, which has its own article.

And none of them is a short course. Stopping has consequences that are covered separately.

The ones that are not registered

Several compounds circulate with names that sound like the above — retatrutide among them. It appeared by name in Costa Rica's July 2026 health warning on unregistered peptides.

A molecule still in clinical trials has no registration anywhere, which means no dossier has been assessed for quality, safety or efficacy. The absence of a registration number is not a technicality; it is the entire difference between a medicine and a substance.

What this page is not

It is not advice on which agent suits you, and we have deliberately not published doses, prices or comparisons framed as recommendations. Which molecule — if any — is appropriate depends on your measurements, your other conditions, your other medicines and what you are actually trying to achieve.

That is a conversation with a physician who has seen your bloodwork. Anyone offering the choice before the assessment has the order wrong.