Peptide dosage basics

Three numbers behind every measurement

Most questions about peptide dosage come down to three numbers: the amount of compound in the vial, the volume of liquid it is dissolved in, and the volume drawn from it. This guide explains how each is written and how they connect. It covers measurement only, and it gives no dose, schedule or protocol for any person.

How amounts are written

Milligrams and micrograms. A microgram is one thousandth of a milligram, so 0.5 mg is 500 mcg and 2 mg is 2,000 mcg. Converting every figure to the same unit before calculating keeps a factor of 1,000 from slipping into the result.

Milliliters and cc. A cubic centimeter (cc) is the same volume as a milliliter. Vials and syringes may use either abbreviation.⁶

Two kinds of units. The word covers two different things. A drug can be measured in units: insulin is, and standard U-100 insulin holds 100 units of insulin in each milliliter, the most common strength according to the American Diabetes Association.¹⁷ Most insulin syringes are scaled to match, so each unit mark is 0.01 mL.¹ For any liquid other than U-100 insulin, those marks still measure volume only. FDA has warned that instructions with some compounded semaglutide give doses in syringe units rather than milligrams or milliliters, and that what those units represent can vary with the product's concentration.²

International units on vials. Some vials are labeled in international units (IU) instead of milligrams. In this catalog that applies to HCG (5000 IU), HGH (10 IU) and HMG (75 IU). An IU counts biological activity, not weight: the Menopur (menotropins) label, for example, states 75 IU of FSH activity and 75 IU of LH activity per vial, measured by bioassays in rats.¹¹ For somatropin (HGH), the WHO International Standard assigns 3.0 IU per mg.¹² The sources behind this guide give no such figure for HCG or HMG, so those vials are worked in IU, with concentration written as IU per mL.

Concentration links amount and volume

Three formulas cover nearly every calculation:

• Concentration = amount in the vial ÷ volume of diluent
• Amount in a given volume = concentration x volume
• Volume for a given amount = amount ÷ concentration

An example with neutral numbers shows why concentration has to be written down. A vial holding 6 mg dissolved in 2 mL gives 3 mg/mL, which is 3,000 mcg/mL, and 0.1 mL of it holds 0.3 mg. Dissolve the same 6 mg in 3 mL and the concentration falls to 2 mg/mL, so the same 0.1 mL holds 0.2 mg. The volume did not change; the amount in it did. A volume or a unit count, on its own, says nothing about the amount.

The reconstitution guide covers the mixing step, including why a powder's peptide content can be lower than its fill weight.

Reading a U-100 syringe

Because U-100 means 100 units in 1 mL, each unit mark is 0.01 mL. FDA's own example is a 5-unit measure on a U-100 syringe, which is 0.05 mL.¹² The table below converts volume to units and nothing else; the amount of compound on each line depends on the concentration.²

Barrel size and scale vary. embecta, one maker, sells insulin syringes with 1 mL, 0.5 mL and 0.3 mL barrels, and its 0.3 mL barrel can be had with half-unit marks.⁵ On a U-100 scale those barrels hold up to 100, 50 and 30 units. MedlinePlus treats each small line on a standard 1 mL insulin syringe as 1 unit,¹ but the numbers printed on the barrel in hand are the ones to read. The scale also assumes U-100: embecta's rule is that U-500 insulin always goes with a U-500 syringe.⁵

The American Diabetes Association lists trouble reading the units on a syringe among the drawbacks of syringes and vials.⁸ Insulin syringes are on the supplies page, and the units converter turns mL into U-100 units and back.

Why research vials come with no dose

Under 21 CFR 312.160, an unapproved new drug may be shipped for in vitro tests or laboratory animal research only if it is labeled with a caution ending "Not for use in humans", and the shipper must use due diligence to make sure the buyer regularly runs such tests.⁴ Testing an unapproved drug in people in the US happens under an Investigational New Drug application, the route by which a study sponsor is exempted from the rule that a drug needs an approved marketing application before it crosses state lines.⁹

FDA reports warning companies whose unapproved GLP-1 products, falsely labeled "for research purposes", went straight to consumers for human use, complete with dosing instructions.¹⁰ For these reasons, this site gives no dose, schedule or protocol for any research vial. Each compound's profile in Peptides A to Z gives the doses reported in published studies, along with species, route and length of treatment, and says where no human dose has been established.

Approved medicines: the label and the prescriber

As FDA states the law, a prescription drug may be dispensed only on a licensed practitioner's prescription,³ so for an approved prescription medicine, the dose is the one its prescriber sets, following the label. FDA also notes that approved injectable semaglutide is dosed in milligrams at standard concentrations, and that at the time of its July 2024 alert it came only in prefilled pens.² Label dose schedules for the GLP-1 medicines are on the GLP-1 dosage page, and the HCG, HGH and HMG profiles give their labels' dosing information.

How measuring mistakes happen

In July 2024, FDA reported adverse events, some requiring hospital care, that may be linked to overdoses from dosing errors with compounded injectable semaglutide.² Its findings show how easily the arithmetic goes wrong:

• Most reports described people drawing more than their prescribed dose out of a multiple-dose vial; in those cases they took 5 to 20 times the intended dose.²
• In several reports, people told to measure 5 units (0.05 mL) on a U-100 syringe measured 50 units (0.5 mL), ten times as much.²
• Prescribers also slipped when converting milligrams into units: one wrote 25 units where 5 were meant, while another wrote 20 units in place of 2.²
• Many of these patients lacked experience with self-injection, and FDA said unfamiliarity with drawing from a vial, together with confusion among milliliters, milligrams and units, may have contributed.²

The same traps apply to any measurement in a lab. Each of these checks targets one of them:

1. Write the concentration on the vial when it is mixed, in mg/mL and in mcg/mL.
2. Convert every amount to one unit, mg or mcg, before calculating.
3. Work out the volume first, then the syringe units, then check in reverse: units x 0.01 gives mL, and mL x concentration gives the amount.
4. Use a syringe whose scale fits the volume, as FDA encouraged for prescribed doses.²
5. Let a calculator confirm the arithmetic. The reconstitution calculator gives the concentration, the peptide calculator gives the concentration and the U-100 units for an amount, and the units converter switches between mg, mcg, mL and syringe units. Each one shows its formula.