Insulin syringe units chart: how many units is 1 mg, 250 mcg, 500 mcg

U-100 is a concentration standard for insulin: 100 units of insulin per mL. Insulin syringes are marked to match, so 100 units on the barrel is 1 mL and each unit mark is 0.01 mL. When a peptide is drawn into an insulin syringe, the insulin is irrelevant and only the volume scale remains. One unit is one hundredth of a millilitre of whatever liquid is in the vial.

That is the entire reason units confuse people. On an insulin label, units are a dose, because the concentration is fixed at 100 per mL and everyone's insulin is the same strength. On a peptide vial, the concentration is whatever you made it when you added water, so units are a volume and the dose inside that volume is a separate calculation. Ten units of a 5 mg/mL solution and ten units of a 2.5 mg/mL solution are the same volume holding twice and half as much peptide.

Other syringe types exist (U-40, U-500) but are rare in peptide use. If a syringe is not clearly marked U-100, the numbers on this page do not apply to it. The vast majority of insulin syringes sold for subcutaneous use, and all of the ones peptide vendors bundle, are U-100.

Insulin syringes come in three common sizes. A 1 mL syringe holds 100 units and is marked every 2 units. A 0.5 mL syringe holds 50 units and is usually marked every unit. A 0.3 mL syringe holds 30 units and is marked every unit, often with half-unit lines. The smaller the syringe, the finer the resolution, because the same barrel length is divided into fewer units.

The right syringe is the one where the draw lands in the middle of the scale. A 10 unit draw on a 1 mL syringe is a short plug of liquid at the bottom with 2 unit marks, so reading it to the nearest unit is a guess. The same 10 units on a 0.3 mL syringe is a third of the barrel with half-unit marks. For the mcg-range peptides like BPC-157, ipamorelin and CJC-1295 without DAC, draws are typically 5 to 25 units and the 0.3 or 0.5 mL syringes fit. For mg-range draws like tirzepatide at 100 or 150 units, only the 1 mL syringe works and sometimes two draws are needed.

Needle length and gauge are separate from barrel size and matter for comfort rather than dosing. The injection sites guide covers that side. For the dosing side, the barrel markings are what count, and reading the right scale on the right syringe is the whole skill.

Three steps. First, concentration: vial amount divided by water volume. A 5 mg vial with 2 mL of bacteriostatic water is 2.5 mg per mL. Second, volume: dose divided by concentration. For 250 mcg, convert to mg (0.25 mg), then 0.25 divided by 2.5 is 0.1 mL. Third, units: volume times 100. 0.1 mL is 10 units. Written out: units = (dose mg divided by concentration mg per mL) times 100.

The same formula in mcg avoids the conversion for small doses. 5 mg in 2 mL is 5000 mcg in 2 mL, or 2500 mcg per mL, which is 25 mcg per unit (divide by 100). Then 250 mcg divided by 25 mcg per unit is 10 units. The mcg-per-unit figure is the one worth remembering for a vial you use daily, because every dose from that vial is just the dose divided by that number.

The reconstitution calculator runs all three steps from the vial size, water volume and dose, and the reconstitution guide covers the mixing. The chart at the top of this page is the formula pre-computed for the common combinations. If a vial and water volume is not there, the formula is faster than searching for it.

BPC-157, 5 mg vial, 2 mL water. Concentration 2.5 mg per mL, 25 mcg per unit. The compound page's reported range is 250 to 500 mcg, so 250 mcg is 10 units and 500 mcg is 20 units. With 1 mL of water instead, the concentration doubles to 5 mg per mL, 50 mcg per unit, and the same doses are 5 and 10 units. A 10 mg vial with 2 mL is also 5 mg per mL, so 250 mcg is 5 units.

Ipamorelin, 5 mg vial, 2 mL water. Same 2.5 mg per mL and 25 mcg per unit. The reported range of 100 to 300 mcg is 4 to 12 units. CJC-1295 without DAC at 100 to 200 mcg from the same mix is 4 to 8 units, which is why the CJC-1295 and ipamorelin stack is often drawn into one syringe as 8 to 20 units total. TB-500, 5 mg vial, 1 mL water: 5 mg per mL, so the reported 2 to 2.5 mg loading dose is 40 to 50 units.

Tirzepatide, 10 mg vial, 1 mL water. 10 mg per mL. The 2.5 mg starting step is 25 units, 5 mg is 50 units and 10 mg is 100 units, a full 1 mL syringe. Semaglutide, 5 mg vial, 2 mL water: 2.5 mg per mL, so 0.25 mg is 10 units and 2.4 mg is 96 units. The GLP-1 pages have dedicated grids: the tirzepatide dosage chart and semaglutide dosage chart.

Most serious peptide dosing errors come from one habit: remembering a dose as a number of units. Someone who learns that their BPC-157 dose is 10 units has learned it for one vial at one water volume. When the next vial is 10 mg instead of 5 mg, or they add 1 mL instead of 2 mL, 10 units is now 500 mcg or 1 mg, double or quadruple what they intended. Nothing on the syringe looks different.

The GLP-1 drugs are where this does the most damage because the doses are larger and the vials come at more concentrations. The FDA has reported overdoses from compounded semaglutide and tirzepatide where patients drew the units intended for one concentration from a vial at another, or confused mL with units. Ten units is 0.25 mg of semaglutide at 2.5 mg per mL and 1 mg at 10 mg per mL. The same number, a fourfold difference in dose.

The fix is to remember doses in mcg or mg and recalculate the units every time the vial or the water changes. Write the concentration on the vial when it is mixed. Treat a units figure from a forum, a vendor or a previous prescription as meaningless until it has been checked against the concentration in hand. The beginners guide walks through the full first-vial process, and bacteriostatic water vs sterile water covers what to mix with.

Because the units depend on the water, the water can be chosen to make the units easy. The aim is a draw that sits well inside the syringe scale and lands on a whole unit. For a 5 mg vial and a 250 mcg dose, 2 mL gives 10 units, a clean number on any syringe. For a 10 mg vial and the same dose, 4 mL gives 10 units but may not fit the vial; 2 mL gives 5 units, which works on a 0.3 or 0.5 mL syringe.

For mg-range compounds the problem reverses: too much water and the draw exceeds the syringe. Tirzepatide at 10 mg per mL fits every step up to 10 mg in one 1 mL syringe; at 5 mg per mL it fits only up to 5 mg. The compound pages list a standard water volume for each vial size that keeps the common doses in a sensible range, and the peptide dosage chart shows the reported dose next to the vial so the two can be matched.

Whatever the choice, it should be made once per vial and written down. A vial mixed at an unusual concentration to get a clean number is fine as long as the number on the label is the one used for every draw from it.