mg, mcg, IU and mL: the units on a Webb listing

The unit always belongs to one vial

Whatever the unit, the amount printed in a Webb title describes the content of a single vial. The listing then gives how many vials a box carries, and the box contents are the two multiplied together, as the note on how vial and box amounts add up shows. Reading the unit correctly matters before any arithmetic: a figure in milligrams, a figure in International Units and a figure in millilitres measure three different things and cannot be added, divided or compared with one another.

Milligrams: most of the catalog

Milligrams (mg) measure mass, and 160 of the 174 listings use them. The range is wide: the smallest milligram fill is 0.1 mg (IGF-1 LR3 0.1 mg) and the largest is 1,500 mg (Glutathione 1500 mg), whose box holds 15,000 mg (15 g). Because every milligram listing shares one unit, Webb divides each box price by the box contents and prints a price per mg on the product page. Those figures can be set side by side for listings of the same compound.

Micrograms: the same unit, a thousand times smaller

One milligram is 1,000 micrograms (mcg, sometimes written µg). Supplier documents sometimes give small fills in micrograms; Webb prints every fill in milligrams so the figures line up, and converts where needed. One listing has a fill below 1 mg, shown here in both units.

• IGF-1 LR3 0.1 mg: 0.1 mg = 100 mcg per vial, 1 mg = 1,000 mcg per box.

mcg = mg × 1,000 · mg = mcg ÷ 1,000

The conversion changes nothing about the price. A box price divided by its contents gives the same figure whether the contents are written in milligrams or micrograms; only the number of decimal places differs.

International Units: activity, not mass

An International Unit (IU) is defined separately for each substance by a reference standard. It describes a quantity of activity, not a weight, so there is no general factor for turning IU into milligrams, and an IU of one compound has nothing to do with an IU of another. Webb lists 9 IU listings (EPO, HCG, HGH 191AA (Somatropin) and HMG). For these, the product page splits the box price over the IU it contains and prints the result per IU, which can only be compared with other fills of the same compound.

Millilitres: listings sold by volume

5 listings are liquids sold by volume, stated in millilitres (mL). The listing gives the volume of one vial and nothing about how much of any component that volume contains, so Webb works out no per-mg figure for them. The price per vial and the box contents in mL are still printed, and they are fair to compare between liquid listings, as long as you remember they compare volume only.

Blends add up in milligrams

A blend title names two or more components with an amount each. Those amounts are milligrams within one vial, and the listing’s fill is their sum. The note on reading blend names covers the cases where a title states a total but not the split.

Checking a listing yourself

1. Find the unit after the amount in the title: mg, IU or mL (a fill in mcg is shown as a fraction of a mg).
2. Multiply the fill by the vials in the box to get the box contents in that unit.
3. Split the box price over the box contents for a per-mg (or per-IU) figure; skip this step for mL listings.
4. Compare the result only with listings of the same compound in the same unit.

The figures on this page are drawn from the live catalog each time it loads, so the counts and tables above match the product pages they link to.