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Insulin syringe units chart
Units to mL to mg, with the reconstitution tables that answer "how many units is my dose?" - the most-asked question in every peptide and TRT group.
The short answer
On a U-100 insulin syringe, 1 unit = 0.01 mL. Always. 100 units = 1 mL. That never changes, whatever is in the vial.
What changes is how much drug is in each unit, and that depends on your reconstitution:
mcg per unit = (vial mg × 10) ÷ mL of water added
So a 5 mg vial with 2 mL of bacteriostatic water is 25 mcg per unit, and a 250 mcg dose is 10 units. The same vial with 1 mL of water is 50 mcg per unit, and the same 250 mcg dose is 5 units. Units are a volume, not a dose.
Work out your own
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Reference: mcg per unit by reconstitution
The number of micrograms in one unit, for every common vial strength and water volume. Find your row and column once, write it on the vial, and you never have to do the arithmetic again.
| Vial strength | + 1 mL BAC | + 2 mL BAC | + 3 mL BAC | + 5 mL BAC |
|---|---|---|---|---|
| 2 mg vial | 20 mcg | 10 mcg | 6.7 mcg | 4 mcg |
| 5 mg vial | 50 mcg | 25 mcg | 16.7 mcg | 10 mcg |
| 10 mg vial | 100 mcg | 50 mcg | 33.3 mcg | 20 mcg |
| 15 mg vial | 150 mcg | 75 mcg | 50 mcg | 30 mcg |
| 20 mg vial | 200 mcg | 100 mcg | 66.7 mcg | 40 mcg |
| 30 mg vial | 300 mcg | 150 mcg | 100 mcg | 60 mcg |
More water is not weaker medicine - it is the same total drug in a larger volume, so each unit carries less and the dose is easier to measure precisely. For very small doses, deliberately using more water is the standard way to improve accuracy.
Reference: units to draw for a target dose
Read down to your dose, across to your concentration. These are the five reconstitutions that cover most peptide protocols.
| Target dose | 10 mcg/unit 5 mg + 5 mL | 20 mcg/unit 10 mg + 5 mL | 25 mcg/unit 5 mg + 2 mL | 50 mcg/unit 10 mg + 2 mL | 100 mcg/unit 10 mg + 1 mL |
|---|---|---|---|---|---|
| 100 mcg dose | 10 | 5 | 4 | 2 | 1 |
| 200 mcg dose | 20 | 10 | 8 | 4 | 2 |
| 250 mcg dose | 25 | 12.5 | 10 | 5 | 2.5 |
| 300 mcg dose | 30 | 15 | 12 | 6 | 3 |
| 500 mcg dose | 50 | 25 | 20 | 10 | 5 |
| 1000 mcg dose | 100 | 50 | 40 | 20 | 10 |
All figures in units on a U-100 insulin syringe. A blank cell would mean the dose exceeds one syringe.
Reference: testosterone and other oils
Oil-based compounds arrive pre-mixed, so there is no reconstitution step - the concentration is printed on the vial. An insulin syringe still works the same way: mg per unit = concentration ÷ 100.
| Weekly dose | 100 mg/mL 1 mg per unit | 200 mg/mL 2 mg per unit | 250 mg/mL 2.5 mg per unit |
|---|---|---|---|
| 50 mg / week | 50 u 0.50 mL | 25 u 0.25 mL | 20 u 0.20 mL |
| 80 mg / week | 80 u 0.80 mL | 40 u 0.40 mL | 32 u 0.32 mL |
| 100 mg / week | 100 u 1.00 mL | 50 u 0.50 mL | 40 u 0.40 mL |
| 120 mg / week | 120 u 1.20 mL | 60 u 0.60 mL | 48 u 0.48 mL |
| 150 mg / week | 150 u 1.50 mL | 75 u 0.75 mL | 60 u 0.60 mL |
| 200 mg / week | 200 u 2.00 mL | 100 u 1.00 mL | 80 u 0.80 mL |
Full weekly volume. If you split into two injections a week, halve every number; for every-third-day dosing, divide by 2.33.
Insulin syringes are fixed-needle and fine-gauge, which suits subcutaneous injection of thin oils. Thicker carriers and intramuscular delivery generally need a larger gauge - see the TRT injection guide.
Check the barrel says U-100
Every figure on this page assumes a U-100 syringe: 100 units per mL. U-40 syringes are still sold for veterinary insulin and deliver 40 units per mL, so one unit is 0.025 mL rather than 0.01 mL.
Draw a dose calculated for U-100 using a U-40 syringe and you take roughly 2.5× the volume you intended. The syringes look nearly identical. Read the barrel before every new box.
Why "units" causes so much confusion
Insulin syringes are marked in units because they were designed for one drug at one standard strength: U-100 insulin, where 1 unit genuinely is a fixed dose of insulin. For everything else - peptides, testosterone, hCG, GLP-1s drawn from a vial - a unit is only a volume marking. It says how much liquid you drew, not how much drug.
That is why "how many units should I take?" has no answer without two more numbers: what was in the vial, and how much liquid you added. Two people on an identical 250 mcg protocol will correctly draw very different unit counts if one used 1 mL of bacteriostatic water and the other used 3 mL. Neither is wrong. When someone posts a unit count without their reconstitution, the number is not transferable.
The three-step method
- 1. Concentration. Vial mg ÷ mL of water = mg per mL.
- 2. Per unit. mg per mL ÷ 100 = mg per unit. Multiply by 1000 for mcg per unit.
- 3. Units. Your dose ÷ the per-unit amount = units to draw.
Write the result on the vial label in marker as soon as you reconstitute. Nearly every dosing error in this space happens weeks later, when someone is tired and reconstructing the maths from memory.
Choosing a syringe size
All U-100 syringes use the same unit spacing, so the only question is barrel capacity - and smaller is more accurate, because the same units are spread over more physical distance.
- 0.3 mL (30 units) - typically marked every 1 unit. Best choice for peptide doses under 30 units.
- 0.5 mL (50 units) - usually marked every 1 unit. Good general-purpose size.
- 1 mL (100 units) - often marked every 2 units. Use only when the dose genuinely needs the volume.
If your dose lands under about 5 units in a 1 mL syringe, you are measuring at the limit of what you can read. Reconstituting with more water moves the same dose into a comfortable range - that is a legitimate accuracy fix, not a dilution of your protocol.
Frequently asked questions
How many units is 1 mL on an insulin syringe?
On a U-100 insulin syringe, 1 mL is 100 units. That is the definition of U-100, so 1 unit is always 0.01 mL, 10 units is 0.1 mL, and 50 units is 0.5 mL. This is true on every U-100 syringe regardless of its barrel size - a 0.3 mL, 0.5 mL and 1 mL syringe all use the same unit spacing, they just hold 30, 50 and 100 units respectively.
How many units is 250 mcg of a peptide?
There is no fixed answer, because units measure volume and mcg measures mass. It depends entirely on how much bacteriostatic water you added. Example: a 5 mg vial reconstituted with 2 mL of bacteriostatic water gives 2.5 mg/mL, which is 25 mcg per unit, so 250 mcg is 10 units. The same 5 mg vial reconstituted with 1 mL gives 50 mcg per unit, so 250 mcg is 5 units - half as many for the same dose. Always compute from your own reconstitution.
What is the formula for units per dose?
mcg per unit = (vial strength in mg x 10) / mL of bacteriostatic water added. Then units to draw = your dose in mcg / mcg per unit. Worked example: a 10 mg vial with 2 mL of water is (10 x 10) / 2 = 50 mcg per unit; a 200 mcg dose is 200 / 50 = 4 units.
What is the difference between a U-100 and a U-40 syringe?
U-100 syringes deliver 100 units per mL (1 unit = 0.01 mL). U-40 syringes, still sold for veterinary insulin, deliver 40 units per mL (1 unit = 0.025 mL). If you draw a dose calculated for U-100 using a U-40 syringe you will take roughly 2.5 times the intended volume. Check the barrel is printed U-100 before you use it - this is the single most dangerous mix-up on this page.
How many units is 100 mg of testosterone?
It depends on the oil concentration printed on the vial. At the common 200 mg/mL, each unit is 2 mg, so 100 mg is 50 units (0.5 mL). At 100 mg/mL each unit is 1 mg, so 100 mg is 100 units - a full 1 mL syringe. At 250 mg/mL each unit is 2.5 mg, so 100 mg is 40 units. Read the concentration on your own vial rather than assuming 200 mg/mL.
Which insulin syringe size should I use?
Pick the smallest barrel that holds your dose, because the markings are further apart and easier to read accurately. A 0.3 mL syringe holds 30 units and usually marks every single unit; a 0.5 mL holds 50 units; a 1 mL holds 100 units and often marks every 2 units. Measuring 8 units in a 0.3 mL syringe is meaningfully more precise than measuring it in a 1 mL syringe.
Sources & further reading
- FDA - safe use of insulin syringes, on matching syringe markings to product concentration
- DailyMed - Bacteriostatic Water for Injection labeling (0.9% benzyl alcohol preservative, multiple-dose vial terms)
- ISMP - cautions on measuring non-insulin products in insulin syringes
- USP General Chapter <797> - sterile compounding and beyond-use dating standards
- OptiPin tools: reconstitution calculator · blend calculator · vial longevity · storage & shelf life
The conversion arithmetic on this page is exact and unit-definitional - it follows from U-100 meaning 100 units per mL. What it cannot verify is what is actually in your vial. Underfilled or mislabelled vials are common enough in this space that the calculation should be treated as the floor of your diligence, not the ceiling.
Not medical advice. This is a unit-conversion reference, not a dosing recommendation. It does not tell you what dose to take, whether a compound is appropriate for you, or whether it is legal where you live. Doses should be set with a prescriber, and nothing here should be used to start, change, or stop a medication.
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Enter the vial and the water once. Every future dose shows the units to draw, on the dose card, on your phone - no account, nothing in the cloud.
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