Free tool
Peptide reconstitution & dosage calculator
Pick a goal or search for your peptide, see its published protocols and smart reconstitution guidance, then get the exact units to draw on any syringe size — no account, no signup.
New to this? Start here — see which peptides match your goal, and exactly what reconstituting one actually involves.
A 5 mg vial + 2 mL water, dosed at 250 mcg:
Draw to 10 units
= 0.10 mL on a U-100 syringe
Blends
The total peptide in the vial — the mg number on the label (e.g. 5 mg). This is your whole supply, not one dose.
The sterile water you add to dissolve the powder (this is called reconstituting). More water makes small doses easier to measure.
How much you take in one injection. 1 mg = 1000 mcg.
For educational purposes only. Not medical advice.
Peptide basics
Common questions
Reconstitution, bacteriostatic water, injection basics, and more — plain-English answers to what people ask most before their first vial.
What does 'reconstituting' a peptide mean?
Most peptides ship as a freeze-dried (lyophilized) powder, not a ready-to-inject liquid. Reconstituting means adding a liquid — usually bacteriostatic water — to dissolve that powder back into a solution you can draw into a syringe. The calculator above does the resulting math: how concentrated the solution ends up, and how many syringe units that comes out to for a given dose.
What is bacteriostatic water?
Bacteriostatic water is sterile water with a small amount of benzyl alcohol (typically 0.9%) added as a preservative. That preservative is what makes it different from plain sterile water: it inhibits bacterial growth between uses, so a reconstituted vial can safely be drawn from multiple times over its use window instead of only once.
How is it different from sterile (static) water?
Sterile water has no preservative. Once you add it to a vial, that vial is a single-use, same-session mix — any peptide left afterward isn't protected against contamination on a second draw. Bacteriostatic water's preservative is what allows multi-dose use over days or weeks instead.
How do I know how many units to draw on my syringe?
It comes down to concentration: how many micrograms of peptide end up in each milliliter of liquid once you've reconstituted the vial, divided by how many micrograms you're aiming to take. A more concentrated mix means fewer units for the same dose; a more dilute mix means more units. That's exactly the calculation the tool above runs for you — enter your vial size, water volume, and target dose, and it returns the units to draw for whichever syringe you're using.
How long does a reconstituted vial last?
It varies by compound, storage temperature, and manufacturer guidance — some peptides are stable for weeks refrigerated, others are far more sensitive and should be used within days. There's no single universal number. Peplo's catalog carries the specific recommended window and storage guidance for each compound it supports, and any printed insert or your pharmacy is the authoritative source for the exact vial you're holding.
What's the difference between subcutaneous and intramuscular injection?
Subcutaneous means into the fatty layer just under the skin, typically with a short, thin needle — common for many peptides. Intramuscular means into muscle tissue, using a longer needle that goes deeper. Which route applies to a given compound and protocol is set by whatever specific guidance you're following, not a general rule — this is background on what the terms mean, not a recommendation for any particular peptide.
Why do people rotate injection sites?
Repeatedly injecting the exact same spot is commonly avoided because it can lead to localized irritation, tissue changes, or discomfort over time. Rotating between a few different sites is a widely used practice for spreading that out. What rotation schedule or site selection makes sense for your situation is worth discussing with a healthcare provider or pharmacist.
Any handling basics worth knowing?
Swab the vial's rubber stopper with an alcohol wipe before each draw. Inject the bacteriostatic water slowly down the inside wall of the vial rather than directly onto the lyophilized powder, and swirl or gently roll the vial to dissolve it — many peptides degrade if shaken vigorously. Keep reconstituted vials refrigerated between uses unless the specific compound's guidance says otherwise.
Is using a vial the same as using an Ozempic or Zepbound pen?
No. Both can involve subcutaneous injection, but a prefilled GLP-1 pen ships at a fixed, manufacturer-set concentration with the device controlling the dose for you. A vial-based peptide puts that step in your hands: the vial's strength, how much liquid you add, and what that means for your syringe all have to be worked out before you draw anything. That's the exact gap this calculator — and the accompanying guide on coming from a GLP-1 pen — are built to close.
Educational only, not medical advice. For guidance specific to your situation, talk to a qualified healthcare provider or pharmacist.
Want this calculator to remember your stack?
The Peplo app saves your vials, tracks inventory and expiry, and reminds you when a dose is due — the calculator above is built in, not a separate step.
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