How Peptide Reconstitution Works
Peptides are typically supplied as lyophilized (freeze-dried) powder in sealed vials. Before injecting, you must dissolve the powder in bacteriostatic water (BAC water) — sterile water containing 0.9% benzyl alcohol as a preservative that allows multi-use of the vial. The amount of water you add determines the concentration of your solution.
The key formula is simple: Concentration (mg/mL) = Vial Size (mg) ÷ BAC Water Added (mL). If you have a 5 mg vial and add 2 mL of BAC water, your concentration is 2.5 mg/mL or 2,500 mcg/mL. All the dosing math flows from this single number.
The Insulin Syringe System
Peptides are injected subcutaneously (under the skin, typically on the abdomen or thigh) using insulin syringes. The most common size is a 100-unit syringe, where 100 units = 1.0 mL. So if you need 0.10 mL, you draw to the 10-unit line. This calculator converts your dose into units automatically based on your concentration.
| Vial Size | BAC Water | Concentration | 200 mcg dose = | 250 mcg dose = |
|---|
| 5 mg | 1 mL | 5,000 mcg/mL | 4 units | 5 units |
| 5 mg | 2 mL | 2,500 mcg/mL | 8 units | 10 units |
| 5 mg | 5 mL | 1,000 mcg/mL | 20 units | 25 units |
| 10 mg | 2 mL | 5,000 mcg/mL | 4 units | 5 units |
| 10 mg | 5 mL | 2,000 mcg/mL | 10 units | 12.5 units |
💡 Pro Tip — Add Less Water for More Convenience: Using less BAC water creates a more concentrated solution, so you draw smaller volumes. Many researchers prefer adding 1–2 mL to a 5 mg vial (2,500–5,000 mcg/mL concentration) so each dose is only 4–10 syringe units. This minimizes injection volume and is easier to measure accurately on small syringes.
Reconstitution Best Practices
Always inject BAC water slowly down the side of the vial — never directly onto the peptide powder, as force can denature (destroy) the peptide. Swirl gently rather than shaking. Once reconstituted, store in the refrigerator (not frozen) and use within 4–6 weeks for most peptides. The benzyl alcohol in BAC water keeps it sterile through multiple uses.
Units vs Milligrams vs Micrograms
This is where most people get confused. Here's the complete conversion chain: 1 mg = 1,000 mcg. On an insulin syringe: 1 unit = 0.01 mL, so 100 units = 1.0 mL. When you see a dose like "250 mcg of BPC-157," you convert that to a volume based on your concentration, then convert that volume to syringe units. Our calculator handles all three steps simultaneously.
Peptide Categories and Common Protocols
Growth Hormone Secretagogues
CJC-1295 and Ipamorelin are the classic "GH peptide stack" — one stimulates the release signal (GHRH analog), the other amplifies the pulse (GHRP). Together they produce significantly more GH output than either alone. Standard protocol: 100–200 mcg CJC-1295 (no DAC) + 200 mcg Ipamorelin, injected together 2–3 times daily on an empty stomach. A 12-week cycle with a 4-week off period is typical. CJC-1295 with DAC has a multi-day half-life, so it's dosed once weekly at 1,000–2,000 mcg instead.
GLP-1 / Weight Loss Peptides
Tirzepatide, Semaglutide, and Retatrutide are the blockbuster weight loss peptides. These are long-acting and injected once weekly. Dosing always starts low and escalates slowly over months to allow the body to adapt and minimize GI side effects. Tirzepatide typically starts at 2.5 mg weekly and increases by 2.5 mg every 4 weeks up to 15 mg. Retatrutide is triple-agonist (GIP/GLP-1/glucagon receptor) — the most potent of the class and dosed even more conservatively, starting at 2 mg weekly.
Healing Peptides
BPC-157 (Body Protection Compound) is derived from a gastric protein and shows remarkable healing properties across tendon, ligament, muscle, gut, and neurological tissue in research. It can be injected subcutaneously or directly at/near an injury site. TB-500 (Thymosin Beta-4) promotes cell migration and differentiation — often stacked with BPC-157 for synergistic healing. The newer Pentadeca Arginate (PDA) offers similar benefits to BPC-157 with potentially improved stability.
| Peptide | Category | Typical Dose | Frequency | Half-Life |
|---|
| BPC-157 | Healing | 200–500 mcg | 1–2x daily | ~4 hours |
| TB-500 | Healing | 2–5 mg | 2x/week (loading) | ~4–5 days |
| CJC-1295 (no DAC) | GH Peptide | 100–200 mcg | 2–3x daily | ~30 min |
| Ipamorelin | GH Peptide | 100–300 mcg | 2–3x daily | ~2 hours |
| CJC-1295 (w/ DAC) | GH Peptide | 1,000–2,000 mcg | Once weekly | ~7–8 days |
| Semaglutide | GLP-1 | 0.25–2.4 mg | Once weekly | ~7 days |
| Tirzepatide | GLP-1/GIP | 2.5–15 mg | Once weekly | ~5 days |
| Retatrutide | Triple Agonist | 2–12 mg | Once weekly | ~6 days |
| Sermorelin | GH Peptide | 200–500 mcg | Daily (bedtime) | ~10 min |
| PT-141 | Sexual Health | 0.5–2 mg | As needed (pre) | ~6–12 hours |
⚠ Important — GH Peptide Timing: GHRH/GHRP peptides must be injected on an empty stomach (2+ hours after eating, 30–60 minutes before eating) to avoid blunting the GH pulse. Carbohydrates and fats significantly suppress GH release. The best injection windows are upon waking, pre-workout, and before bed. Missing this timing is the most common reason people get suboptimal results with GH peptides.
Frequently Asked Questions
How much BAC water should I add to my peptide vial?
The amount doesn't affect how many doses you get — it only changes your concentration. Most researchers add 1–2 mL per 5 mg vial. Using 1 mL gives 5,000 mcg/mL concentration (each 250 mcg dose = 5 units). Using 2 mL gives 2,500 mcg/mL (250 mcg = 10 units). Use less water if you want smaller, easier-to-measure injections. Use more if you're working with very small doses and need to spread the volume for easier measurement.
What is bacteriostatic water and why can't I use regular water?
Bacteriostatic water (BAC water) contains 0.9% benzyl alcohol as a preservative, which prevents bacterial growth across multiple uses of the same vial. Regular sterile water (WFI) is also acceptable for reconstitution but has no preservative — once opened, it must be used immediately or discarded. Tap water, distilled water, or saline should never be used as they are not sterile or are not isotonic. BAC water is widely available at pharmacies and online — 30 mL vials are the most practical size.
How long does a reconstituted peptide vial last in the refrigerator?
Most reconstituted peptides remain stable for 4–6 weeks when refrigerated at 34–40°F (1–4°C) and protected from light. Peptides in BAC water generally last longer than those in plain sterile water due to the antimicrobial benzyl alcohol. Never freeze a reconstituted vial — ice crystals can denature the peptide structure. Lyophilized (dry powder) peptides, if kept refrigerated and away from moisture, can retain potency for 2+ years unopened.
Why are my syringe units coming out as a decimal (e.g., 7.5 units)?
This happens when your concentration doesn't divide evenly into your desired dose. For example, a 250 mcg dose with 3,333 mcg/mL concentration gives 7.5 units. The simplest fix is to adjust your BAC water amount to create a "cleaner" concentration. Adding 2 mL to a 5 mg vial gives 2,500 mcg/mL — where 250 mcg = exactly 10 units. Many researchers deliberately choose their water volume to create round numbers on the syringe.
Can I mix multiple peptides in the same syringe?
Many peptides can be mixed in the same syringe if they're compatible and the combined volume is manageable (typically under 0.3 mL). Common stacks drawn together include CJC-1295 + Ipamorelin, and BPC-157 + TB-500. Draw each peptide separately from its vial into the same syringe. However, some combinations should be kept separate — GLP-1 class peptides (Tirzepatide, Semaglutide) are high-dose (in mg) and are not typically stacked with mcg-class peptides in the same injection.
What is the difference between subcutaneous (sub-Q) and intramuscular (IM) injection?
Sub-Q injections go into the fat layer just under the skin — pinch the skin at the abdomen or thigh and inject at a 45-degree angle with a short (5/16" or 8mm) needle. IM injections go into muscle tissue (typically the quad, glute, or deltoid) at a 90-degree angle using a longer needle. Most peptides work equally well via either route. Sub-Q is preferred for most researchers due to ease, less pain, and slower absorption that mimics more natural secretion patterns. BPC-157 is sometimes injected near the injury site for localized healing effects.