TB-500 Reconstitution Calculator

Mixing TB-500: What to Know Before You Reconstitute

1. 01

   Bacteriostatic water vs. sterile water

   Bacteriostatic water is sterile water containing 0.9% benzyl alcohol, a preservative that inhibits bacterial growth in the vial after it has been punctured. Sterile water has no preservative and is generally treated as single use. Since a TB-500 vial is typically drawn from across several weeks, bacteriostatic water is the standard choice. The weekly cadence makes this more consequential than it is with daily compounds, because the vial spends longer in service between the first draw and the last.

2. 02

   How much water to add

   Water volume does not change how much TB-500 is in the vial. A 5 mg vial holds 5 mg whether you add 1 mL or 3 mL. What changes is concentration, and therefore the size of your draw. Because TB-500 doses are usually in the milligram range, the draws are larger than with mcg-dosed peptides, which is why people often reach for a slightly higher water volume to keep the syringe from filling up.

   Vial	Water	Concentration	Per unit	2 mg draw	2.5 mg draw
   5 mg	1 mL	5.0 mg/mL	50 mcg	40 units	50 units
   5 mg	2 mL	2.5 mg/mL	25 mcg	80 units	100 units
   10 mg	2 mL	5.0 mg/mL	50 mcg	40 units	50 units
   10 mg	3 mL	3.33 mg/mL	33.3 mcg	60 units	75 units

   Notice what happens at 5 mg in 2 mL: a 2.5 mg draw fills a 100-unit syringe completely. That is the practical argument for less water with TB-500, and it is exactly what the calculator above shows visually through the syringe fill.

3. 03

   Mixing technique

   Angle the needle so the water runs down the inside wall of the vial rather than landing directly on the powder, then let it sit or swirl gently until fully dissolved. Shaking is avoided with peptides generally, since it foams the solution. TB-500 usually dissolves readily and should end up clear with no visible particles. A vial that stays cloudy after gentle swirling is one most people will not use.

4. 04

   Storage before and after mixing

   Unopened lyophilized vials are typically kept cool and dark. Once reconstituted, the vial goes in the refrigerator, and the widely followed convention is to discard after about 28 days, a window that comes from punctured bacteriostatic water rather than from the peptide itself. Weekly dosing makes this worth watching: a vial reconstituted for a weekly protocol may still contain solution when the 28 day mark arrives, so the date matters more here than with daily compounds. Writing the mix date on the vial, or letting PepKit count it down for you, avoids the arithmetic entirely.

5. 05

   The syringe

   U-100 insulin syringes are standard, where 100 units equal 1 mL and each unit is 0.01 mL. Because TB-500 draws are larger, the 1 mL 100-unit syringe is the usual choice rather than the smaller 0.3 mL or 0.5 mL sizes, which can be too small to hold a full dose at common concentrations.

6. 06

   Common mistakes worth avoiding

   The recurring ones: adding so much water that a single dose no longer fits the syringe, mixing mg and mcg when converting a dose, shaking rather than swirling, losing track of the reconstitution date across a multi week vial, and reusing an old draw calculation after changing the water volume on a new vial.