For GLP-1 cost comparisons, 13 fills lasting 28 days cover 364 days, while 12 calendar-month charges cover a year. At a hypothetical $300 per fill, that is $3,900 for 13 fills, or $325 per calendar month using the 52-week convention. Those figures are arithmetic, not a provider quote.
This distinction is practical: Lilly’s current Zepbound savings terms define a month as 28 days.[1] Our monthly GLP-1 price guide helps compare programs once their billing periods are aligned.
The simple conversion
Multiply a four-week price by 13, then divide by 12. That converts the price into a calendar-month equivalent for a 52-week year. For a precise 365-day rate, use price × 365 ÷ 28 ÷ 12; the result is slightly higher.
Do not confuse a normalized rate with the exact number of transactions in your bank statement. The starting date, refill timing and available supply affect when charges fall. The 364-day method is transparent and useful for comparing offers with the same assumption.
A worked example with no hidden provider claim
Suppose Program A charges $300 every four weeks and Program B charges $315 each calendar month, with otherwise identical included services. Program A normalizes to $325 per month; Program B remains $315. The lower headline in this example produces the higher yearly cost.
Now add a hypothetical $25 monthly membership to Program A: $325 plus $25 equals $350. If shipping is charged per fill, multiply that fee by 13 as well. If a visit is charged once per year, divide that amount by 12.
Dose changes matter more than tidy arithmetic
A starting price cannot stand in for the maintenance price unless the seller confirms the same rate applies. Write separate rows for the expected dose stages and ask the clinician which schedule is appropriate. Do not choose a dose to satisfy a pricing example.
Some programs quote one rate across doses, while others publish a ladder. Flat-rate GLP-1 pricing explains the distinction. Also check prepayment terms before dividing a package total by its advertised number of months.
Keep the payment route consistent
A cash quote, an insured copay and a conditional savings offer may describe different transactions. Healthcare.gov explains that prescription coverage depends on the plan’s drug list and pharmacy arrangements.[2]
Compare the same medication, formulation, dose, supply period and included care. Mark a temporary discount separately from the ongoing rate. If insurance is involved, check whether cash spending receives deductible credit before deciding that the smallest immediate payment is your lowest annual cost.
Henry Meds offers a useful counterexample to equating billing with delivery. Its program document pairs monthly fees with semaglutide shipment allowances measured over 70 or 90 days. Record both dates. A supply window alone does not tell you how often your card is charged.