Washout period

A washout period is the gap you leave between stopping one drug and doing something that requires it to be gone — starting another medication, undergoing a procedure, or trying to conceive. Its length comes directly from half-life, and on the weekly GLP-1s that makes it long.

The clearest example is on the Wegovy label, which instructs patients being treated for cardiovascular risk reduction or weight reduction to discontinue at least two months before a planned pregnancy, giving the long half-life of semaglutide as the reason. Semaglutide remains in circulation for roughly five to seven weeks after a final 2.4 mg dose, so two months is not a cautious rounding — it is the arithmetic.

Tirzepatide clears faster, with a half-life near five days, and orforglipron faster still at roughly 29 to 49 hours. Liraglutide, at about 13 hours, is nearly gone in three days. This is one of the few places where an older or shorter-acting drug has a genuine advantage: if you are planning a pregnancy or facing frequent procedures, a shorter washout is a real consideration.

The mistake people make is treating a washout as a formality to be shortened. The other mistake is applying one drug’s number to another. A two-month rule from a semaglutide label tells you nothing useful about a tirzepatide plan, and neither number is the same as the pre-procedure hold your anesthesiologist will ask for, which is a different and much shorter calculation about stomach contents rather than drug clearance.

Raise it early. If pregnancy is anywhere in your plans, ask before the first prescription rather than after. If you are switching drugs, ask whether an overlap or a gap is intended and at what dose the new drug starts. Our washout calculator, pre-op stop-date calendar and pregnancy washout review handle each case.