Last updated: June 2026 · Reviewed June 2026 · Built by the InjectBuddy team
How does the TB-500 calculator work? mg dose to syringe units
To turn a TB-500 (thymosin beta-4) dose into syringe units, divide the milligrams you want by the vial's concentration in mg/mL to get milliliters, then multiply by 100 for U-100 units. A 5 mg vial reconstituted in 2 mL is 2.5 mg/mL, so a 1 mg dose is 0.4 mL, or 40 units. This guide explains what TB-500 is, walks through the three-step calculation, provides a dose-to-units reference table by water volume, works through seven examples, and answers the questions people ask most — with one honest caveat throughout: thymosin beta-4 is a preclinical peptide with no approved human dose, so every figure here is a maths reference, never a dosing recommendation.
Key takeaways
- Concentration (mg/mL) = vial milligrams ÷ BAC water milliliters. It is fixed once you reconstitute.
- Units = (dose mg ÷ concentration mg/mL) × 100 on a U-100 syringe.
- More BAC water = lower concentration = more units for the same milligrams. The dose itself never changes.
- TB-500 has no validated human dose; treat every figure here as arithmetic only.
Run your own vial through the peptide reconstitution calculator to convert any TB-500 mg dose to units instantly.
What TB-500 actually is
TB-500 is the research label commonly used for thymosin beta-4, a 43-amino-acid peptide whose primary, well-characterised role inside cells is sequestering G-actin — it is the main intracellular actin-buffering peptide in vertebrate cells (Hannappel 2007). It has been studied as a regenerative agent across skin, cornea, heart and brain tissue, and a 2012 review catalogs those repair activities and proposed therapeutic uses (Goldstein et al. 2012). Much of the cardiac interest comes from animal work showing systemic thymosin beta-4 can limit myocardial cell death and support repair (Shrivastava et al. 2010), with related studies linking it to coronary vessel development and neovascularisation (Smart et al. 2007).
The critical word across all of that literature is preclinical. These are cell-culture and animal-model findings. There is no regulatory approval for general human use, no agreed dose, and no validated schedule. That is exactly why this guide stays on the maths: it shows you how a stated milligram figure maps to syringe units, and nothing about whether any figure is safe or appropriate for a person.
How this is calculated
Reconstitution maths has three moving parts: the milligrams in the vial, the milliliters of bacteriostatic (BAC) water you add, and the dose you want. The vial milligrams are fixed by the manufacturer. The water volume is your choice, and it sets the concentration. The dose is whatever figure you are working to.
- Concentration in mg/mL = vial milligrams ÷ BAC water milliliters.
- Draw volume in mL = dose milligrams ÷ concentration mg/mL.
- Units on a U-100 syringe = draw volume mL × 100 (because 1 mL = 100 units).
Working in micrograms can be cleaner for small TB-500 doses: 1 mg = 1,000 mcg, so a 5 mg vial in 2 mL is 2,500 mcg/mL. A 500 mcg dose is then 500 ÷ 2,500 = 0.2 mL = 20 units. BAC water matters here because it carries a benzyl alcohol preservative that slows bacterial growth after the stopper is pierced; it does not re-sterilise the vial, so clean technique still applies (Pfizer label; CDC injection safety).
TB-500 mg dose to units, by reconstitution volume
This chart assumes a single 5 mg TB-500 vial and shows how the same milligram dose lands on different unit marks depending on how much BAC water you added. Read down your water column to find the units for a given dose.
| Dose | +1 mL (5 mg/mL) | +2 mL (2.5 mg/mL) | +3 mL (1.667 mg/mL) | +5 mL (1 mg/mL) |
|---|---|---|---|---|
| 0.25 mg | 5 units | 10 units | 15 units | 25 units |
| 0.5 mg | 10 units | 20 units | 30 units | 50 units |
| 1 mg | 20 units | 40 units | 60 units | 100 units |
| 2 mg | 40 units | 80 units | 120 units | 200 units* |
| 2.5 mg | 50 units | 100 units | 150 units | 250 units* |
*Any figure above 100 units will not fit a single 1 mL U-100 syringe and would need more than one draw — usually a sign the concentration is too dilute for that dose. Figures are arithmetic, not a recommendation to inject any of them.
Why the water volume changes the units
The milligrams in the vial are fixed. Bacteriostatic water only changes the volume those milligrams are dissolved into, which changes the concentration and therefore how many units carry a given dose. Reading across any row of the table makes this concrete: a 1 mg dose is 20 units at 5 mg/mL but 100 units at 1 mg/mL — five times the syringe volume for the identical milligram amount. The dose did not change; only its dilution did.
Worked examples
5 mg vial · 2 mL · 1 mg dose
Concentration = 5 ÷ 2 = 2.5 mg/mL. Volume = 1 ÷ 2.5 = 0.4 mL. Units = 0.4 × 100 = 40 units.
5 mg vial · 1 mL · 1 mg dose
Concentration = 5 ÷ 1 = 5 mg/mL. Volume = 1 ÷ 5 = 0.2 mL. Units = 0.2 × 100 = 20 units. Half the water, half the units.
5 mg vial · 3 mL · 500 mcg dose
Concentration = 5,000 mcg ÷ 3 = 1,667 mcg/mL. Volume = 500 ÷ 1,667 = 0.30 mL. Units = 30 units.
2 mg vial · 1 mL · 0.5 mg dose
Concentration = 2 ÷ 1 = 2 mg/mL. Volume = 0.5 ÷ 2 = 0.25 mL. Units = 0.25 × 100 = 25 units.
10 mg vial · 5 mL · 2 mg dose
Concentration = 10 ÷ 5 = 2 mg/mL. Volume = 2 ÷ 2 = 1.0 mL. Units = 100 units — exactly fills a 1 mL U-100 syringe.
5 mg vial · 2.5 mL · 250 mcg dose
Concentration = 5,000 mcg ÷ 2.5 = 2,000 mcg/mL. Volume = 250 ÷ 2,000 = 0.125 mL. Units = 12.5 units — round-friendly to read.
Reverse check · 5 mg vial · 2 mL · 60 units drawn
60 units = 0.6 mL. Dose = 0.6 × 2.5 mg/mL = 1.5 mg. Working backwards from the syringe confirms what a mark represents.
Common mistakes
The most frequent error is copying someone else's unit number without matching their water volume. "40 units of TB-500" only means a specific milligram amount once you know the concentration; at 5 mg/mL that 40 units is 2 mg, but at 2.5 mg/mL it is 1 mg. The mark is identical, the dose is not.
The second is mixing mg and mcg mid-calculation. 1 mg is 1,000 mcg, so a "0.5" you treat as milligrams when the source meant micrograms is off by a factor of a thousand. Keep one unit system from the vial label to the syringe. The third is ignoring dead space — the small volume trapped in the needle hub — which matters more when draws are tiny. None of this makes a preclinical compound appropriate to use; it only makes the arithmetic honest.
So, how does the TB-500 calculator work?
The TB-500 calculator works by dividing your milligram dose by the vial concentration (mg/mL) to get the draw volume in milliliters, then multiplying by 100 to read U-100 syringe units. Concentration is fixed the moment you add BAC water: a 5 mg vial plus 2 mL gives 2.5 mg/mL, so a 1 mg dose is always 0.4 mL (40 units) from that vial. Run your own numbers through the peptide reconstitution calculator to convert any TB-500 mg dose to units instantly.
Frequently asked questions
How does the TB-500 calculator work?
How many units is a 1 mg TB-500 dose?
Is there an established human dose for TB-500?
Does adding more BAC water change the dose?
Why work in micrograms for TB-500?
Sources
- Goldstein AL, Hannappel E, Sosne G, Kleinman HK. Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applications. Expert Opin Biol Ther. 2012.
- Hannappel E. beta-Thymosins. Ann N Y Acad Sci. 2007.
- Shrivastava S, Srivastava D, Olson EN, DiMaio JM, Bock-Marquette I. Thymosin beta4 and cardiac repair. Ann N Y Acad Sci. 2010.
- Smart N, Risebro CA, Melville AA, et al. Thymosin beta-4 is essential for coronary vessel development and promotes neovascularization. Ann N Y Acad Sci. 2007.
- CDC. Safe injection practices to prevent transmission of infections to patients. CDC clinical guidance.
This guide is a calculation reference for general education only and is not medical advice. TB-500 (thymosin beta-4) is a preclinical, investigational peptide with no approved human dose; nothing here recommends its use. Always follow a qualified prescriber's instructions.