Why per-pack prices are so hard to compare

Ask two providers what a month costs and you get two numbers that look comparable and are not. One is quoting a starting strength, one a maintenance strength. One bundles the consultation and delivery, one adds them at checkout. One sells a single multi-dose pen, one sells four single-dose pens in a box. One is quoting an introductory rate that lapses after two fills. The headline figure hides all of it.

The milligrams are the one thing that stays honest. The standard weekly pens hold four doses of their labelled strength, which the official product information states plainly: the tirzepatide KwikPen "contains 4 doses", and the 2.4 mg semaglutide pen holds "9.6 mg (four doses) of semaglutide". Multiply the strength by the doses and you have the medicine in the box. Divide the price by that and you have a number you can hold against another quote for the same thing.

The Wegovy pill goes in its own column, not the same league table

This is the change most likely to catch someone out, so it is worth being blunt. The pill is the same drug as the Wegovy injection, semaglutide, and its milligram numbers are enormous by comparison. A maintenance month is 25 mg a day, which is 750 mg in a 30-tablet pack. A maintenance month of the injection is 2.4 mg a week, which is 9.6 mg. That is about 73 times as many milligrams by mouth.

The reason is absorption. The product information for the 25 mg tablets says oral semaglutide "has a low absolute bioavailability and a variable absorption", so most of what you swallow never reaches your bloodstream. The two doses were chosen to land in the same place: in the modelling submitted for approval, 82.2% of people taking oral semaglutide 25 mg in the OASIS 4 trial reached drug exposure inside the same range as people on the 2.4 mg weekly injection in STEP 1 (Overgaard et al., 2026). An indirect comparison of the two trials, funded by the manufacturer, put the difference in weight loss at about one percentage point in the injection's favour, with a confidence interval crossing zero (Plotkin et al., 2026). There is no head-to-head trial, so that is an estimate rather than a measurement.

Put those two facts together and the arithmetic consequence is unavoidable. Roughly 73 times the milligrams for a similar effect means the tablet's cost per mg comes out at a fraction of the injection's, whatever either of them is priced at. A cheaper-looking per-mg figure here is a fact about how the drug is absorbed, not a discount. That is why this tool keeps two tracks, labels one "per mg injected" and the other "per mg swallowed", and never puts them in one table. If you want to compare the two forms, compare what a month costs, not what a milligram costs.

The maths, in full

There is no hidden formula. It is four divisions.

• Milligrams in the pack = strength × doses in the pack. A 10 mg pen with 4 doses holds 40 mg. A 30-tablet pack of 25 mg holds 750 mg.
• Cost per mg = what you paid ÷ milligrams in the pack.
• Cost per day = what you paid ÷ the number of days that pack covers you.
• Cost per 4 weeks = cost per day × 28.

Put the consultation and delivery fee into what you paid. It is money that left your account to get the medicine into your hands, and leaving it out is how two prices that look a long way apart turn out to be level.

Time covered is a separate question from doses

Most price tools assume you reorder every month. Plenty of people do not. Some are on a schedule where they take less than the labelled strength each week, and a single pen can cover far longer than four weeks. That is why this calculator asks how many doses the pack holds and how long it covers you as two different questions.

The effect is worth understanding. The milligrams in a pack are fixed, so stretching it out does not change cost per mg at all. It changes cost per day, and it changes how often you reorder. If that is your situation, the per-day and per-4-week figures are the ones that reflect what you actually spend, and the per-mg figure is the one to hold against a quote. How you dose is a decision for your prescriber. It is not a lever to pull for budget reasons on your own.

Which way cost per mg runs as the dose goes up

Higher strengths are usually cheaper per milligram, because nobody charges six times as much for six times the medicine. On the Zepbound figures recorded here, the dearest strength per mg is 2.5 mg at $29.90 per mg, and the cheapest is 15 mg at $11.65 per mg. A 15 mg pack holds 60 mg against 10 mg in a 2.5 mg pack.

It does not fall smoothly, though, and that is worth seeing rather than being told the tidy version. Going from 7.5 mg to 10 mg, cost per mg goes up, from $16.63 to $17.48 per mg, because the pack price steps up faster than the milligrams do. So the general pattern holds and the specific step does not. Read the table rather than the rule.

Either way, this is arithmetic about pricing and nothing more. It is not a reason to move up the ladder. In SURMOUNT-1, mean weight at 72 weeks fell by 15.0% on tirzepatide 5 mg, 19.5% on 10 mg and 20.9% on 15 mg, against 3.1% on placebo (Jastreboff et al., 2022). The gap between 10 mg and 15 mg is a good deal smaller than the gap between 5 mg and 10 mg, and side effects are part of the picture too. Which dose you are on is a clinical decision your prescriber makes with you.

The tablet ladder behaves the same way within its own track. The dearest strength per mg swallowed is 1.5 mg at $3.31 and the cheapest is 25 mg at $0.399. Those are swallowed milligrams and belong only next to each other.

Never compare cost per mg between the two different drugs

Tirzepatide and semaglutide are dosed on completely different scales, so their milligram numbers mean different things. In the SURMOUNT-5 head-to-head trial, 751 adults were randomised to the highest tolerated dose of tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg) for 72 weeks. Mean weight fell by 20.2% with tirzepatide and 13.7% with semaglutide (Aronne et al., 2025). Very different milligrams, very different results. Cost per mg is a tool for comparing two quotes for the same medicine, by the same route, at the same strength. Used across medicines it tells you nothing.

What a price does not tell you

A cost per mg is one number about one thing. It says nothing about whether a provider checks your history properly, whether it can keep you supplied when a strength goes short, whether the price you see holds after the consultation, or what happens if you want to cancel halfway through. Those are worth as much as the money, and sometimes more.

The figures used here are the manufacturers' own published self-pay list prices, read in July 2026. They are what someone paying without insurance is quoted, and they are not what you will pay with a commercial plan or through Medicare, which depends on your formulary and your deductible. Retail pharmacy and telehealth prices sit above the self-pay list, so treat these as a floor rather than a market range, and check the current terms before you rely on them.

Safety, plainly

This page is information about prices. It is not medical advice, and it is not a recommendation to start, change, stretch or stop any medicine. If cost is the pressure you are under, say so to your prescriber or doctor before you change anything. There are usually options worth discussing, and stopping suddenly has consequences of its own that are better planned than discovered.

Two more things worth saying because they come up whenever price does. Never share a pen with anyone else, even at the same dose, and never buy these medicines from anywhere that will sell them without a proper prescription check. A price that undercuts everything on this page usually means something has been skipped.