Peptide dosing math: mcg, mg, IU and syringe units

Three unit systems show up on peptide product sheets and syringes: micrograms (mcg), milligrams (mg), and international units (IU). Dose math gets confusing because instructions switch between them mid-sentence. Once the three are separated, the math itself is arithmetic.

Weight units: mcg and mg#

Peptides are dosed in weight. A typical BPC-157 dose is 250 mcg (micrograms). MK-677, an oral secretagogue (studies have shown it is active by mouth), is dosed in milligrams: in a two-year trial in older adults, 25 mg once daily has been shown to raise GH and IGF-1 into the young-adult range, and it was associated with a rise in fasting glucose. The conversion is constant:

1 mg = 1,000 mcg

Most peptides are dosed in mcg because the typical therapeutic range is below 1 mg. A 200 mcg dose of Ipamorelin is easier to read and discuss than 0.2 mg. A 25 mg dose of MK-677 is easier than 25,000 mcg. The units follow the scale.

Product sheets and vial labels vary in which unit they use. A "5 mg" BPC-157 vial contains 5,000 mcg. A "500 mcg" Ipamorelin dose is 0.5 mg. When a protocol specifies a dose, note the unit and stick with it for the rest of the math.

Volume units: mL and syringe units#

Reconstituted peptides are liquid. Syringes measure volume. The standard peptide syringe is a U-100 insulin syringe, which marks 100 units per mL. The 0.3 mL, 0.5 mL and 1 mL barrels all use the same scale; a 1 mL barrel holds 100 units, a 0.5 mL barrel 50, a 0.3 mL barrel 30.

100 units = 1 mL

Other mappings follow:

• 50 units = 0.5 mL
• 20 units = 0.2 mL
• 10 units = 0.1 mL

That's all "units" means on an insulin syringe, a finer division of a milliliter. It has nothing to do with the weight of peptide inside.

The concentration bridge#

Weight (mcg or mg) and volume (mL or units) connect through concentration. Concentration is what you set when you choose a BAC water volume for reconstitution.

Concentration = peptide weight in vial ÷ BAC water volume

Examples:

• 5 mg BPC-157 + 2 mL BAC water = 2.5 mg/mL = 2,500 mcg/mL
• 10 mg Ipamorelin + 2 mL BAC water = 5 mg/mL = 5,000 mcg/mL
• 10 mg Tirzepatide + 3 mL BAC water = 3.33 mg/mL = 3,333 mcg/mL

Once you have the concentration, any dose converts to syringe units with one formula:

Syringe units = (target dose in mcg ÷ concentration in mcg/mL) × 100

Peptide dose calculation flow

Worked example#

Vial: 5 mg BPC-157 + 2 mL BAC water (concentration = 2,500 mcg/mL)

• 250 mcg dose: (250 ÷ 2,500) × 100 = 10 units
• 500 mcg dose: (500 ÷ 2,500) × 100 = 20 units
• 1,000 mcg (1 mg) dose: (1,000 ÷ 2,500) × 100 = 40 units

Same vial reconstituted with 5 mL of BAC water instead of 2 mL (concentration = 1,000 mcg/mL):

• 250 mcg dose: (250 ÷ 1,000) × 100 = 25 units
• 500 mcg dose: (500 ÷ 1,000) × 100 = 50 units

More BAC water dilutes the peptide. More dilution means more syringe units per dose, easier to measure, harder to overdose by a small margin. Two of the most common errors are reading mg as mcg and mixing up syringe units (volume) with IU (potency); the concentration bridge above prevents both when applied step by step.

International units: where they matter and where they don't#

IU (international unit) is a potency unit defined by biological activity, not by weight. Different peptides have different weight-to-IU ratios. The unit exists because early insulin, HCG, and HGH products varied in purity and potency, so a biological standard was needed. The WHO International Standards programme maintains the reference preparations the IU is calibrated against, including the International Standard for chorionic gonadotropin that HCG potency is assayed against. (US HCG labels state potency in "USP units," which are equivalent.)

Compounds that use IU:

• HCG, dosed and labeled in IU or USP units (e.g., 5,000 and 10,000 unit vials)
• HGH (somatropin), often discussed in IU, especially outside the US. US labels dose it in mg; the conversion is about 3 IU per mg.

Peptides that do not use IU:

• All GH secretagogues (CJC-1295, Ipamorelin, Tesamorelin, Sermorelin, GHRP-2, GHRP-6, Hexarelin), dosed in mcg or mg (tesamorelin's label dose is 1.28 to 1.4 mg depending on formulation), plus oral MK-677 in mg
• All GLP-1 class (semaglutide, tirzepatide, retatrutide), dosed in mg
• Healing peptides (BPC-157, TB-500, GHK-Cu, KPV), dosed in mcg or mg
• Longevity peptides (NAD+, Epitalon, DSIP), dosed in mcg or mg

For the IU peptides, the reconstitution math is the same, but substituting IU for mcg:

• 5,000 IU HCG + 5 mL BAC water = 1,000 IU/mL
• 250 IU dose: (250 ÷ 1,000) × 100 = 25 units on the syringe

Practical habits that prevent dosing errors#

Three habits make peptide dose math reliable:

1. Stick to one unit system per protocol. If the peptide is dosed in mcg, keep all math in mcg. If it's in mg, stay in mg. Converting mid-calculation is where zeros go missing.
2. Draw in daylight, not from habit. Insulin syringe markings are fine. A glance at the "wrong" mark under bad lighting is a common cause of over- or under-dosing.
3. Use the calculator even once for a new protocol. The first dose of a new peptide should be measured against what Klarovel's peptide calculator says the draw should be. Once the sanity check aligns with the math you're doing in your head, the routine takes over.

One-minute summary#

• Peptide dose is weight: mcg or mg, with 1 mg = 1,000 mcg
• Syringe unit is volume: 100 units = 1 mL on a U-100 insulin syringe
• Concentration bridges the two: mcg per mL is the number you set during reconstitution
• Dose in syringe units = (dose in mcg ÷ concentration in mcg/mL) × 100
• IU is a potency unit. Used for HCG and, outside US labeling, HGH. Not used for the peptides in the Klarovel catalog.

For every specific case, the units converter handles mcg/mg/IU conversions, and the peptide calculator handles the full vial-to-syringe math in one step. The titration calculator adds a week-by-week escalation schedule on top. Between those three tools and the intake questionnaire, every dosing decision that matters has a structured answer.

Get the math right once. The rest of the protocol gets easier from there, and the dose math fits into the wider picture of what peptide therapy involves.