Micrograms to U-100 syringe units and back at the concentrations peptide vials produce, what one unit holds, and the one FDA label that printed the table.
"Mcg to units" asks how many marks on an insulin syringe hold a stated number of micrograms. Micrograms are a mass and units are a volume, so the answer always runs through one more number: the concentration of the solution in the barrel. This page states the formula in microgram terms, gives the table both ways at the concentrations peptide vials produce, and checks the method against the one FDA label found that printed a microgram-to-unit chart (read 2026-10-15). It reports arithmetic; it recommends no amount.
The same method in milligrams, for GLP-1 amounts, is on mg to units; the step from a microgram figure to millilitres alone is on mcg to mL; and the barrels and their markings are on the insulin syringe units page.
A U-100 insulin syringe holds 100 units per millilitre, so one unit is 0.01 mL whatever the liquid. Then:
units = amount (mcg) ÷ concentration (mcg/mL) × 100
and in reverse, mcg = units ÷ 100 × concentration (mcg/mL).
Working in mcg/mL rather than mg/mL removes the one step where most errors happen, the mixing of the two mass units. A vial labelled 5 mg holds 5,000 mcg; dissolved in 2 mL it is 2,500 mcg/mL, and every microgram figure can then be divided straight into it. The mg to mcg tables cover that first conversion on its own.
What one unit holds
The shortest form of the answer is the content of a single mark. It is the concentration divided by 100.
| Concentration |
Where it comes from |
mcg in 1 unit |
mcg in 10 units |
| 250 mcg/mL |
teriparatide pen (label) |
2.5 |
25 |
| 600 mcg/mL |
SYMLIN vial, 2005 (label) |
6 |
60 |
| 1,000 mcg/mL |
SymlinPen (label); 1 mg vial + 1 mL; 5 mg vial + 5 mL |
10 |
100 |
| 1,667 mcg/mL |
5 mg vial + 3 mL |
16.7 |
167 |
| 2,000 mcg/mL |
2 mg vial + 1 mL; 10 mg vial + 5 mL |
20 |
200 |
| 2,500 mcg/mL |
5 mg vial + 2 mL |
25 |
250 |
| 3,333 mcg/mL |
10 mg vial + 3 mL |
33.3 |
333 |
| 5,000 mcg/mL |
5 mg vial + 1 mL; 10 mg vial + 2 mL |
50 |
500 |
The research-vial rows are arithmetic on the labelled powder and the water added; the label rows are the concentrations printed on approved products. The range across the table is twentyfold, which is the range a "10 units" reading can mean.
Micrograms to units
The amounts in the rows are the round figures that recur in microgram-dosed searches. The four columns are the concentrations a 1, 2, 5 or 10 mg research vial produces at common water volumes.
| Amount |
1,000 mcg/mL |
2,000 mcg/mL |
2,500 mcg/mL |
5,000 mcg/mL |
| 50 mcg |
5 units |
2.5 units |
2 units |
1 unit |
| 100 mcg |
10 |
5 |
4 |
2 |
| 200 mcg |
20 |
10 |
8 |
4 |
| 250 mcg |
25 |
12.5 |
10 |
5 |
| 300 mcg |
30 |
15 |
12 |
6 |
| 500 mcg |
50 |
25 |
20 |
10 |
| 1,000 mcg |
100 |
50 |
40 |
20 |
As sentences: at 2,500 mcg/mL, 250 mcg = 0.1 mL = 10 units. At 5,000 mcg/mL, 250 mcg = 0.05 mL = 5 units, and 500 mcg = 10 units. At 1,000 mcg/mL, 1,000 mcg fills a whole 1 mL syringe at 100 units.
What the table shows that a single answer does not: every cell of a microgram amount up to 1,000 mcg fits one 1 mL syringe at these concentrations, the opposite of the milligram GLP-1 amounts on the mg page, where dilute vials run out of barrel. The microgram problem is the other end of the scale. At 5,000 mcg/mL, 50 mcg is a single unit, and a single unit is the smallest mark on the finest barrels.
Units to micrograms
The reverse lookup answers "how many mcg is 10 units" and its neighbours.
| Units (mL) |
1,000 mcg/mL |
2,000 mcg/mL |
2,500 mcg/mL |
5,000 mcg/mL |
| 1 (0.01 mL) |
10 mcg |
20 mcg |
25 mcg |
50 mcg |
| 2 (0.02 mL) |
20 |
40 |
50 |
100 |
| 5 (0.05 mL) |
50 |
100 |
125 |
250 |
| 10 (0.10 mL) |
100 |
200 |
250 |
500 |
| 15 (0.15 mL) |
150 |
300 |
375 |
750 |
| 20 (0.20 mL) |
200 |
400 |
500 |
1,000 |
| 25 (0.25 mL) |
250 |
500 |
625 |
1,250 |
| 50 (0.50 mL) |
500 |
1,000 |
1,250 |
2,500 |
Every row spans a fivefold range in this table alone. A unit count read off a syringe carries no information about micrograms until the concentration is known, and the concentration is known only from the vial's labelled amount and the water added to it.
A labelled check: the SYMLIN chart
One FDA-approved label is known to have done this conversion in print. The 2005 SYMLIN label (pramlintide acetate, NDA 21-332, the 5 mL vial at 0.6 mg/mL; FDA label PDF read 2026-10-15) told prescribers that, with a U-100 insulin syringe, a chart was to be used "to measure the microgram dosage in unit increments", and preferred the 0.3 mL barrel "for optimal accuracy". Its Table 8:
| Dose prescribed |
U-100 syringe |
Volume |
| 15 mcg |
2.5 units |
0.025 mL |
| 30 mcg |
5.0 units |
0.050 mL |
| 45 mcg |
7.5 units |
0.075 mL |
| 60 mcg |
10.0 units |
0.100 mL |
| 120 mcg |
20.0 units |
0.200 mL |
The formula reproduces every row: 15 ÷ 600 × 100 = 2.5. Drugs@FDA lists that vial as discontinued, and on the same read lists both pens as discontinued too (2026-10-15). The pens that replaced it, SymlinPen 60 and SymlinPen 120, hold pramlintide at 1,000 mcg/mL (openFDA label effective 2019-12-18), so the same 15 mcg is 0.015 mL, or 1.5 units on a U-100 scale. The chart was correct for its vial and wrong for every other concentration, which is the general point in one product. The current instructions also state that SYMLIN is not to be transferred from the pen into a syringe; the pen dials the microgram dose itself.
Teriparatide is the second labelled case. Its pens are 560 mcg in 2.24 mL, 250 mcg/mL, for 28 daily doses of 20 mcg (openFDA, labels effective 2025-05-27 and 2025-06-01). On a U-100 scale 20 mcg would be 0.08 mL, or 8 units, and the carton says the contents are not to be transferred to a syringe. Both labels make the same choice: a fixed microgram dose delivered by a device, so that no one converts it by hand.
Where mcg-to-units answers go wrong
- Micrograms read as milligrams. 250 mg at 2,500 mcg/mL is 100 mL, or 10,000 units. Any unit count above 100 for a microgram figure in a peptide vial points at this slip.
- The concentration of the wrong vial. A chart copied from a page that assumed 2 mL of water is off by half or double for a vial mixed with 1 or 4 mL, exactly as the SYMLIN chart is off for its own pen.
- Total blend micrograms. In a two-peptide vial, a microgram figure for the blend converts per component only by each one's share of the mass; the blend calculator works the shares.
- Syringe units read as IU. A syringe unit is a volume; an international unit is a defined biological activity. They coincide only for U-100 insulin. The IU conversions set out the standards that define an IU for other substances.
What this page does not do
It recommends no microgram amount and no concentration. The figures in the tables are round numbers chosen to show the arithmetic, not dose suggestions; per-compound figures, each with its source and date, are on the dosage pages. For a specific vial the reconstitution calculator does the arithmetic from the labelled amount and the water entered. Medibact's bacteriostatic water is the diluent its compound guides are written around; decisions about amounts belong with a prescriber.
Sources and dates
Opened 2026-10-15: the SYMLIN label for NDA 21-332 dated 3/14/05 as an FDA label PDF (Table 8 and How Supplied); the Drugs@FDA record for NDA021332 through openFDA (vial 3 mg/5 mL and both pens listed discontinued); the SymlinPen label through openFDA (set id 4aea30ff-eb0d-45c1-b114-3127966328ff, effective 2019-12-18; dosage forms and Instructions for Use); the teriparatide injection and BONSITY labels through openFDA (effective 2025-05-27 and 2025-06-01; dosage forms, how supplied, carton). All unit and microgram arithmetic by this site. Corrections go to the contact page.
