This is educational information, not medical advice, and The Peptide University does not sell peptides, supplies, or supplements. Many compounds discussed here are sold as “research chemicals” and are not approved for human use outside of clinical trials. Laws vary by country, and nothing here is a recommendation to obtain or use anything. Talk to a qualified clinician about your own situation.
This explains the math and terminology people encounter so you can understand discussions and catch dangerous errors. It is not instructions to prepare or use any compound, and sterile preparation of anything injected carries real infection risk. If you're doing anything that breaks the skin, that's a conversation for a medical professional.
The short version
- Reconstitution = adding sterile water to a freeze-dried powder to make a solution.
- Concentration depends on two numbers: the amount of compound and the volume of water you add.
- The most dangerous error in this whole space is confusing mcg and mg (1 mg = 1000 mcg).
- Powder is stable; solution is not. Storage rules change once it's mixed.
What reconstitution means
Many peptides ship as a lyophilized (freeze-dried) powder because that's the most stable form. To turn it into something measurable, sterile water is added — this is reconstitution. Add the water gently down the side of the vial rather than blasting it onto the powder, and swirl rather than shake. That's the whole idea; the intimidating part is only the arithmetic that follows.
Which water
- Bacteriostatic water (BAC) — sterile water with a small amount of preservative, commonly used because it allows multiple withdrawals over time.
- Sterile water for injection — no preservative; typically single-use.
Which one is appropriate depends on the compound and how it's being handled — another detail worth confirming from a reliable source, not guessing.
The concentration math
This is genuinely simple once you see it once. Concentration is just amount ÷ volume.
If a vial holds 5 mg of compound and you add 2 mL of water, the concentration is 5 mg ÷ 2 mL = 2.5 mg per mL.
To find how much liquid contains a given amount, flip it around: desired amount ÷ concentration = volume to draw.
Want 0.5 mg from a 2.5 mg/mL solution? 0.5 ÷ 2.5 = 0.2 mL.
Because doses are often discussed in micrograms (mcg) but vials are labeled in milligrams (mg), a decimal-place slip can mean a 10× or 100× error. Always convert deliberately: 1 mg = 1000 mcg. When a number feels surprising, stop and recheck the units before anything else.
Reading syringe units
Insulin syringes are marked in units (IU), not milliliters, which trips people up. On a standard U-100 syringe, 100 units = 1 mL, so 10 units = 0.1 mL. If your math gives you a volume in mL, converting to syringe units is just multiplying by 100 (for U-100). Getting comfortable moving between mg/mL, mL, and units is the single practical skill this article is really about.
Storage & stability
| State | Typical handling | Relative stability |
|---|---|---|
| Sealed lyophilized powder | Cool, dark, dry; freezer for long term | Most stable |
| Reconstituted solution | Refrigerated, protected from light | Limited — use within a window |
| Repeated warming / light | Avoid | Accelerates degradation |
The general rule: powder forgives, solution doesn't. Once reconstituted, most compounds have a much shorter usable life and need refrigeration. Label the vial with the date you mixed it so you're never guessing.
Common questions
QDoes the amount of water change the dose?
It changes the concentration, not the total amount in the vial. More water = more dilute = you draw a larger volume for the same dose. The compound quantity is fixed; water only sets how it's spread out.
QWhy do people use bacteriostatic water?
The preservative lets a vial be accessed multiple times over a period without the same contamination concern as preservative-free water. Suitability still depends on the compound.
QWhat if my calculation seems off?
Stop and recheck units first — mcg vs mg is the usual culprit. It's completely reasonable to have someone double-check the arithmetic. There's no prize for rushing.
Questions & comments
No account, no login — leave a name or stay anonymous. Ask a question, add something the article missed, or answer someone else. Be kind and cite sources where you can.