TB-500 Reconstitution Calculator (mg → units)
A 10 mg vial of TB-500 mixed with 2 mL of bacteriostatic water holds 5,000 mcg/mL, so a 2.5 mg dose is 0.5 mL — 50 units on a U-100 insulin syringe. Change the vial, water or dose below, or read the chart for other mixes.
TB-500 dilution chart: 2.5 mg in units
| Vial | + 1 mL water | + 2 mL water | + 3 mL water | Doses per vial |
|---|---|---|---|---|
| 5 mg | 50 U 0.5 mL · 5,000 mcg/mL | 100 U 1 mL · 2,500 mcg/mL | 150 U 1.5 mL · 1,667 mcg/mL over 1 mL — more than one syringe | 2 |
| 10 mg | 25 U 0.25 mL · 10,000 mcg/mL | 50 U 0.5 mL · 5,000 mcg/mL | 75 U 0.75 mL · 3,333 mcg/mL | 4 |
1 mL = 100 units on a U-100 syringe. Water volume changes the units per dose, never the number of doses in the vial.
Measuring TB-500: the math that matters
TB-500 is counted in milligrams, not micrograms, and the amounts people quote are large enough to fill a syringe fast. With a 10 mg vial and 2 mL of bacteriostatic water the solution is 5,000 mcg/mL, so 2.5 mg is 0.5 mL, or 50 units on a U-100 insulin syringe. The same 2.5 mg from a 5 mg vial with 2 mL is 100 units, a full 1 mL syringe, and the vial is empty after two doses.
Because the numbers are big, the usual advice to add more water for easier reading works against you here. A 10 mg vial with 3 mL puts 2.5 mg at 75 units, and a 5 mg vial with 3 mL would need 150 units, more than one syringe. With TB-500 the question is usually how little water you can use while still dissolving the powder and keeping each draw comfortable. 1 mL in a 10 mg vial gives 25 units per 2.5 mg, and 2 mL gives 50.
The biggest mg trap with TB-500 is the research it is often confused with. TB-500 is a short fragment of thymosin beta-4. The human safety study usually cited used the full 43-amino-acid protein given intravenously at 42 to 1,260 mg, which says nothing about how many milligrams of the fragment to draw. Numbers from that study should not go into this calculator.
Vials of TB-500 are sold as research chemicals, so the milligrams on the label are the supplier's claim. If you work from a mix, write the concentration on the vial and keep it refrigerated and out of light, as described in the injection guide below.
Common TB-500 measuring mistakes
- Treating mg and mcg as interchangeable. 2.5 mg is 2,500 mcg; typing 2.5 with mcg selected gives 0.05 units at 5,000 mcg/mL.
- Adding 3 mL to a 5 mg vial and discovering each dose no longer fits in one syringe.
- Using thymosin beta-4 trial doses, which were for a different, much larger molecule given by IV, as TB-500 amounts.
- Recalculating after a vial change but keeping the old units written on the box.
- Splitting a 100-unit dose into two 50-unit draws and forgetting the second.