Is a month of GLP-1 twenty-eight days?

Short answer

For weekly injectable GLP-1 medications, usually yes. Sellers commonly bill by the 28-day supply, which is four weekly doses. A price quoted per month for a weekly injectable therefore usually means the price of a 28-day supply.

Per month, for a weekly injectable, is the price of four weekly doses — a 28-day supply.

Why a week sets the length, not a calendar

A weekly injection is taken once a week. Four of those doses fit into a 28-day supply, so the supply is counted in weeks rather than in the days of a month. Sellers commonly bill by that supply, which is why a pricing page can call it a month while the box underneath holds four doses.

In plain terms: the schedule decides the length. When a medication is dosed weekly, the natural billing unit is four doses, and “month” is being used as a convenient word for that unit rather than as a statement about the calendar.

Thirteen charges, not twelve

A seller who bills every 4 weeks takes 13 charges in a calendar year, not 12. That is not an error or an extra fee. It follows from the length of the cycle: a year holds more than twelve 28-day periods, so a billing cycle tied to 28 days lands thirteen times instead of twelve.

This is the single most useful thing to know when reading a per-month figure on a weekly injectable. The number is honest, but it describes one cycle, and a year contains more than twelve of those cycles. The arithmetic of why a 28-day cycle and a calendar month are not interchangeable is set out in billing intervals, in plain terms.

Tablets are different

Daily oral GLP-1 tablets do not work this way. A tablet is taken every day, so a month of tablets is a real 30-day supply. There are no weekly doses to count and no four-dose unit standing in for a month.

The distinction matters because the same word appears on both kinds of page. “Month” on a weekly injectable points at 28 days; “month” on a tablet product points at 30. Reading one as if it were the other is where a comparison stops being like-for-like.

How to compare two injectable offers

Two steps, in this order.

1. Compare the price per 28-day supply. Put both offers on the same unit — four weekly doses — before setting one against the other, rather than comparing a figure labeled month with a figure labeled otherwise.
2. Check whether the dose changes the price. A program priced at one rate across doses and a program priced by dose are not comparable at the entry dose alone, so confirm which of the two you are looking at.

Neither step requires arithmetic beyond putting both prices on the same unit. What it requires is noticing the unit in the first place.

How this guide records prices

This guide records prices per 28-day supply for weekly injectables, and its methodology says so. That is a deliberate choice, so that a figure published here always corresponds to four weekly doses rather than to whatever a page happened to call a month.

It also means a figure on this site can differ from a figure on a seller’s page without either being wrong: they may be counting different units. Where the two disagree, check which unit each one is stated in before assuming one of them has changed.

Compounded medications are not FDA-approved

Compounded semaglutide and compounded tirzepatide are not FDA-approved. A billing unit is a billing unit; it says nothing about approval. Nothing on this page about 28-day supplies, four weekly doses or 30-day tablet supplies should be read as approval of any compounded preparation.

Why this guide tracks cash prices

This guide records what programs charge in cash for the compounded medications sold now, dates every figure it records, and states the unit each figure is counted in. A per-month quote is noted as a 28-day supply where that is what it is; it is never quietly treated as a calendar month. To see the programs themselves, start with the buyer guide; to see how each charge is read, dated and compared, read how we compare.