Switching Between GLP-1 Drugs

People switch between these drugs constantly — for supply, for cost, for side effects, or because one stopped working. The obvious question is what dose you land on, and the honest answer is that no published equivalence exists. Every conversion chart circulating online is somebody’s arithmetic, not a labeled fact.

Why there is no conversion

Dose equivalence gets established when a regulator is asked to approve one. Nobody has asked, because no manufacturer has an interest in demonstrating that its drug can be swapped for a competitor’s. So the tables do not exist — not because the question is unimportant, but because no one has been required to answer it.

There is also a mechanistic reason not to expect a clean conversion. Tirzepatide acts at two receptors, GIP and GLP-1; semaglutide acts at one. They are not the same drug at different strengths, and a milligram of one has no defined relationship to a milligram of the other. Our tirzepatide timeline covers why even their trial results cannot be read against each other.

A conversion chart implies a relationship that no regulator has approved and no trial has established.

What the labels actually say

What every label does say is how to start — and they all say the same thing in the same shape.

• Start at the lowest dose. Every drug in this class has an opening dose intended to be tolerated rather than to work.
• Escalate no faster than every four weeks. The interval is about the gut adjusting, not about the drug accumulating.
• Increase as tolerated. The labels deliberately leave room for a prescriber to hold or step back.

Applied to a switch, that produces an unwelcome but consistent answer: a new drug is a new titration. Someone comfortable at a high dose of one may still start at the bottom of the other’s ladder, and the weeks that follow can feel like starting over because physiologically they are.

Reasons to switch, ranked by how good they are

1. Side effects you cannot tolerate. The best reason, and now supported by comparative data — drugs in this class differ measurably by symptom, which we cover in the side-effect ranking.
2. Supply. A real and common reason, and the one that leaves people least choice.
3. Cost or coverage. Legitimate, and worth confirming the new price is durable rather than promotional before restarting a ladder.
4. “It stopped working.” The weakest reason on its own, because a plateau is expected rather than a failure — and switching restarts the climb regardless.

What to expect in the gap

These drugs are long-acting, so stopping one does not clear it immediately. Semaglutide has a half-life of about a week, which means meaningful drug remains for several weeks after the last dose. Overlapping two of them is a prescriber’s decision and not a matter of picking a date.

Expect appetite to return before the new drug reaches a working dose. That gap — old drug fading, new drug climbing — is where most of the difficulty of switching actually lives, and knowing it is coming is most of managing it.