What period a monthly price actually covers

Four ways a period gets set, and only one of them is a month

A figure described as monthly is doing one of four things in this market, and they are genuinely different.

It can be a calendar-month subscription, billed on the same date each month. It can be a cycle of a fixed number of weeks, which comes round on its own schedule. It can be the price of a container the seller says lasts a certain number of weeks, which is a quantity rather than a plan. Or it can be a fixed-length course whose total has been divided across its length.

Only the first of those is a month. The other three are periods that happen to be described in monthly language, because monthly is the word buyers shop in.

None of this is concealment. A seller with a four-week cycle is describing its own arrangement accurately. The trouble starts when two such descriptions are placed side by side and read as the same unit.

A four-week cycle comes round thirteen times, not twelve

This is the part that costs money quietly, and it takes no arithmetic on any price to see.

A year holds twelve calendar months. It also holds fifty-two weeks, which is thirteen periods of four weeks.

So a plan billed every four weeks charges you thirteen times across those fifty-two weeks, where a calendar-month plan charges you twelve. That is one extra charge a year, every year, invisible in the figure itself.

Two sellers publishing the identical number, one on a calendar month and one on a four-week cycle, are not charging the same amount over a year. The one on the shorter cycle is charging more, and nothing on either page says so.

The check is simple and it belongs in the comparison rather than after it. Ask how many times you will be billed in a year, not what each bill is.

How long a container lasts is a different clock from how often you are billed

Some prices here are not attached to a billing period at all. They are attached to a container, with a note about how long it is expected to last.

That note is a supply estimate, and it depends on the regimen you are actually prescribed. It is not a promise about a date and it is not a plan you are enrolled in.

Two clocks are running whenever a price is quoted that way. One is how often the seller charges you. The other is how long what arrives lasts. When those two do not line up, you either accumulate containers you have not used or run out before the next charge.

A third clock sits underneath both of them, which is how long a preparation may be used once it has been opened or made up. That window is set by the pharmacy and the labeling rather than by the plan, and it has its own article on this site.

The useful question is not which of the three is right. It is whether the seller has told you where all three sit, because a supply estimate presented as a monthly price has answered only one.

A course has a total, and a subscription does not

A fixed-length course and an open-ended subscription are two different purchases, and they fail to compare in opposite directions.

A course has an end date written into it, so it has a total you can know before you start. What it does not tell you is what happens afterward, which is the part with no figure attached at all.

A subscription has no total. Its cost is whatever you pay multiplied by how long you stay, and how long you stay is a clinical question rather than a commercial one.

To compare the two you have to pick a length of time and hold both against it. That length is not published by anyone, because it is a decision about your own treatment rather than a feature of either offer.

Choose one anyway before you compare. Any horizon you pick consciously is better than the one you inherit by reading two figures that describe different spans.

A course total divided out is not a price you can pay

A fixed-length course is frequently advertised as a per-month figure, and the figure is arrived at by dividing the total by the length.

The number that comes out of that division is honest arithmetic and it is not a rate. Nobody sells one month at it. It exists only as a description of a purchase that is bought whole.

One consequence matters more than the rest. A divided-out figure sorts beautifully in a list of monthly prices, and it will usually sort near the bottom, because a longer commitment buys a lower per-period number almost everywhere.

This site keeps that difference in a tool rather than smoothing it over. The commitment axis separates a rate you can pay once from a rate that exists only inside a longer plan. It is set out on the cost-by-term page, with every seller's own wording printed beside its figure.

The axis in this article is the other one. Two figures can both be payable one period at a time and still cover periods of different lengths.

What the sellers here actually publish

Of the 177 price figures published by the sellers tracked here in September 2026, 28 state their period in weeks rather than in months.

Those 28 are not one pattern. They include containers described as an average four-week supply and containers a page says last about five weeks. They also include programs described as running four to six weeks, a course billed as a ten-week total, and a subscription billed every four weeks.

That count moves whenever a seller is added or changes what it publishes, so read it as a reading taken in one month rather than a property of the market.

The wider point does not move. A period stated in weeks is common enough here that assuming a month is a bad default, and the seller has usually said which it is somewhere on the page.

What to settle before you compare two figures

Find the length of the period each figure covers, in days or weeks, and write it down beside the number.

Count the charges in a year rather than comparing the size of one charge. Thirteen of something is not twelve of it.

Where a price is attached to a container, find what the page says the container lasts, and treat that as a supply estimate rather than a billing term.

Where a course is priced as a whole, ask what the arrangement is after the course ends, because that is the period no figure describes.

Pick a horizon before you compare anything, and use the same one for both sellers.

Then confirm the current figures on each seller's own page. Prices move, plan terms change, and a comparison is a guide to what to check rather than a quote.