Half-Life and Dosing Frequency

What half-life actually means

Half-life is the time it takes for the concentration of a drug in your blood to fall by half.

It is not how long the drug works, and it is not how long it stays in your body. It is one rate, and almost everything else about a dosing schedule follows from it.

Two rules of thumb do most of the work. It takes roughly four to five half-lives of repeated dosing to reach a steady concentration. And it takes roughly the same to clear out after the last dose.

The range in this one hormone family

All figures below are elimination half-lives as stated on each product's FDA label, retrieved in August 2026, or as published for the investigational molecules.

Native GLP-1 — 1.5 to 2 minutes, because dipeptidyl peptidase 4 and neutral endopeptidases degrade it almost immediately¹.

Tesamorelin — 11 minutes in healthy subjects after a single subcutaneous dose².

Pramlintide — approximately 48 minutes in healthy individuals³.

Exenatide — a mean terminal half-life of 2.4 hours⁴.

Liraglutide — approximately 13 hours, which the label describes as making it suitable for once-daily administration¹.

Dulaglutide — approximately 5 days⁵.

Tirzepatide — approximately 5 to 6 days in patients with overweight or obesity⁶.

Semaglutide — approximately 1 week⁷.

That is a spread of roughly four orders of magnitude, from 1.5 minutes to 168 hours, across molecules that all act on the same receptor family.

Three ways to buy time

The labels describe the engineering explicitly, and three approaches do most of the work.

Block the enzyme's grip. The semaglutide label states that the molecule is modified in position 8 to provide stabilisation against degradation by DPP-4⁷. The dulaglutide label describes structural modifications in the part of the GLP-1 sequence responsible for interaction with DPP-4⁵.

Hitch a ride on albumin. Attach a fatty acid so the molecule binds the most abundant protein in blood and stops being filtered out. Liraglutide carries a C-16 fatty acid — palmitic acid — with a glutamic acid spacer at position 26¹. Semaglutide carries a hydrophilic spacer and a C18 fatty di-acid at position 26, and its label calls albumin binding the main protraction mechanism⁷. Tirzepatide carries a C20 fatty diacid, and its label says explicitly that this enables albumin binding and prolongs the half-life⁶.

Bolt it to an antibody. Dulaglutide is a fusion protein: a GLP-1 analog sequence covalently linked to the Fc portion of a modified human IgG4 heavy chain⁵. That takes the molecular weight to approximately 63 kilodaltons, against 4,113.58 g/mol for semaglutide⁷ and 3,751.2 daltons for liraglutide¹.

Note what has happened by the third trick: a 63-kilodalton antibody fusion is not really a peptide any more. See what a peptide is.

Where the long tail actually bites

A long half-life is usually described as convenience. It has two consequences that are not.

Slow onset of steady state. Four to five half-lives of repeated dosing to plateau means a molecule with a one-week half-life takes about a month of weekly injections to reach a stable concentration — separate from any titration schedule the label sets.

Slow washout. The semaglutide label states that with an elimination half-life of approximately 1 week, semaglutide will be present in the circulation for about 5 to 7 weeks after the last dose⁷. The same label directs discontinuing at least 2 months before a planned pregnancy, and gives the long half-life as the reason⁷.

Stopping a weekly drug is not an event. It is a five-to-seven-week taper you do not control.

What the newest molecules are doing with it

Two directions, both away from weekly.

Longer. Maridebart cafraglutide is a long-acting peptide-antibody conjugate, and its phase 2 trial dosed it every 4 weeks, with one arm at every 8 weeks⁸. Petrelintide, a long-acting amylin analog, reported a half-life of approximately 10 days in its phase 1 programme⁹ — against approximately 48 minutes on the label for the approved short-acting amylin analog³. We cover that class in amylin analogs.

Shorter, deliberately. A daily oral GLP-1 does not need a week-long half-life, because the tablet is taken every day. Route and half-life are separate levers — see oral vs injectable peptides.

What half-life tells you about a compound with no label

This is the practical use of the number.

A 2026 review of BPC-157 reports a preclinical ADME study in two species confirming a plasma half-life under 30 minutes, and describes the human pharmacokinetic profile as critically undercharacterised¹⁰.

Under 30 minutes is a real constraint. It says something about how any hypothetical dosing schedule would have to look, and it says nothing at all about whether the compound does anything useful — those are different questions. Our page on healing peptides covers the second one.

The short version

Half-life sets frequency. Frequency sets adherence. Adherence is one of the largest determinants of whether a drug produces its trial result in ordinary life.

That chain is why an eight-fold change in a pharmacokinetic parameter can matter more to a class than a two-point difference in a trial's headline. Our semaglutide, tirzepatide and tesamorelin pages each carry the label detail for their own molecule.