TB-500 Reconstitution — Volume and Concentration Table

Published 2026-09-29 · Lyophile Editorial

Reconstitution math for TB-500 starts with one number: the mass printed on the vial. Diluent volume, final concentration, syringe units — all of it falls out of that single figure. Find your vial size below, pick a diluent volume, read the concentration, convert to units.

The core relationship:

Concentration (mcg/mL) = Peptide mass (mg) × 1000 ÷ Diluent volume (mL)

A U-100 insulin syringe is calibrated so 100 units = 1 mL. So 1 unit = 0.01 mL, and mass per unit = concentration ÷ 100.

TB-500 reconstitution table (5 mg and 10 mg vials)

| Vial size | Diluent added | Concentration | Per unit (U-100) | Per 10 units | |---|---|---|---|---| | 5 mg | 1 mL | 5000 mcg/mL | 50 mcg | 500 mcg | | 5 mg | 2 mL | 2500 mcg/mL | 25 mcg | 250 mcg | | 5 mg | 3 mL | 1667 mcg/mL | 16.7 mcg | 167 mcg | | 5 mg | 5 mL | 1000 mcg/mL | 10 mcg | 100 mcg | | 10 mg | 1 mL | 10,000 mcg/mL | 100 mcg | 1000 mcg | | 10 mg | 2 mL | 5000 mcg/mL | 50 mcg | 500 mcg | | 10 mg | 3 mL | 3333 mcg/mL | 33.3 mcg | 333 mcg | | 10 mg | 5 mL | 2000 mcg/mL | 20 mcg | 200 mcg |

Read left to right and the arithmetic is transparent. 5 mg in 2 mL: 5000 mcg ÷ 2 = 2500 mcg/mL, which is 25 mcg per unit. Double the mass at the same diluent volume and you double the concentration — 10 mg in 2 mL lands at 50 mcg per unit.

The trade-off is resolution versus volume. More diluent gives finer per-unit steps but a larger draw for the same mass. Less diluent gives a compact draw but coarser steps. At 1 mL in a 10 mg vial, one unit is 100 mcg — nothing finer resolves on a standard U-100 barrel. Half-unit markings, where present, halve that floor.

How much bacteriostatic water for a 5 mg TB-500 vial?

5 mg vial + 2 mL bacteriostatic water = 2500 mcg/mL = 25 mcg per unit on a U-100. Bacteriostatic water is preserved with 0.9% benzyl alcohol per USP monograph standards, which is what allows multi-draw use from a single vial. Larger diluent volumes lower per-unit mass proportionally.

2 mL is the common middle ground: 25 mcg/unit divides cleanly and keeps draw volume modest. For finer control, use 3 mL (16.7 mcg/unit) or 5 mL (10 mcg/unit). For the smallest practical draw, 1 mL (50 mcg/unit) — but almost no resolution below that.

Step-by-step: reconstituting a TB-500 vial

1. Read the vial label. Confirm total peptide mass in mg. Only input that matters for the concentration calculation.
2. Choose diluent volume. Common: 1, 2, 3, or 5 mL. Match to the resolution you need from the table above.
3. Swab both stoppers. Alcohol wipe on peptide vial and diluent vial. Air dry — wet stoppers defeat the swab.
4. Vent, then inject slowly. Let the vacuum pull or push diluent down the vial wall, not onto the powder pellet. A direct stream at the lyophilized cake can shear it and foam the solution.
5. Swirl, don't shake. Roll between palms or swirl gently until the cake dissolves. Shaking denatures peptides and creates persistent foam that throws off volume reading.
6. Inspect. Clear solution, no visible particulates. Cloudy or undissolved cake → keep swirling, don't force it.
7. Label with date and concentration. Write 2500 mcg/mL on the vial, not just the date. Future-you will not remember which diluent volume you used.

One failure mode to watch for: injecting diluent fast onto the powder creates a localized high-concentration pocket that dissolves slowly and leaves a stubborn ring of cake at the bottom. Slow and down-the-wall avoids it.

What concentration should I reconstitute TB-500 to?

No single correct concentration — it depends on the resolution your measurement needs and the volume your syringe handles comfortably. 2 mL diluent on a 5 mg vial (2500 mcg/mL, 25 mcg/unit) is a practical default: balances resolution against draw volume. Finer work → 3–5 mL. Compact draws → 1 mL.

Two constraints bound the choice:

• Syringe resolution. On a U-100 barrel, smallest reliably readable increment is typically 1 unit (0.01 mL). Effective measurement floor = per-unit mass.
• Solubility. Extremely high concentrations risk incomplete dissolution. An undissolved fraction silently changes actual concentration.

When in doubt, more diluent is the safer error — costs volume, not accuracy. (I would rather draw 40 units than squint at 4.)

Syringe unit conversion quick reference

Units to draw = Target mass (mcg) ÷ (Concentration ÷ 100)

| Concentration | 100 mcg | 250 mcg | 500 mcg | 1000 mcg | |---|---|---|---|---| | 2500 mcg/mL (25/unit) | 4 units | 10 units | 20 units | 40 units | | 5000 mcg/mL (50/unit) | 2 units | 5 units | 10 units | 20 units | | 1000 mcg/mL (10/unit) | 10 units | 25 units | 50 units | 100 units |

At 2500 mcg/mL, 500 mcg = 20 units. At 5000 mcg/mL, the same 500 mcg = 10 units — half the volume, double the concentration. The diluent volume you choose at reconstitution locks in every draw afterward.

Handling and storage notes

Reconstituted peptide in bacteriostatic water: typically refrigerated at 2–8 °C, protected from light. Benzyl alcohol at 0.9% is what makes repeated draws from one vial defensible; plain sterile water removes that protection and shortens practical use. Avoid freeze-thaw cycling of reconstituted solution — promotes aggregation. Lyophilized powder: generally stored frozen and dry for longer-term holding. Follow the supplier's published stability specification for the specific lot — stability claims vary by vendor and peptide.

For research use only — not clinical guidance.

Where to source bacteriostatic water

• BAC Water Depot — 0.9% benzyl alcohol, USP-grade, multi-vial packs
• MedLab Supply — sterile-filtered bacteriostatic water, single and bulk
• Recon Peptides — bacteriostatic water with lot documentation

Where to source research peptides

• Alpha Amino USA — per-lot HPLC/MS COA, US-shipped
• Lot-Verified Peptides — third-party tested, published COAs
• Research Grade Supply — lyophilized vials with mass-verified labels