Reconstitution math has one formula: milligrams of peptide divided by millilitres of diluent gives the concentration in mg/mL. On a U-100 insulin syringe, 1 unit is 0.01 mL, so each unit holds one hundredth of the concentration. A 10 mg vial with 2 mL of bacteriostatic water is 5 mg/mL, which puts 50 mcg in each unit and 250 mcg in 5 units. The diluent sets the shelf life after opening: pharmacy guidance limits an opened multiple-dose vial to 28 days. This page is arithmetic for research vials, not dosing guidance.
The formula is short: milligrams of peptide ÷ millilitres of diluent = concentration in mg/mL. On a U-100 insulin syringe, 1 unit = 0.01 mL, so every unit carries one hundredth of that concentration. A 10 mg vial mixed with 2 mL of bacteriostatic water is 5 mg/mL, each unit holds 50 mcg, and 250 mcg sits at the 5-unit mark.
Everything below is that formula applied to the vial sizes people ask about most, plus the pharmacy rules that decide how long a mixed vial stays usable. We describe what compounding references and clinical trial protocols do. None of it is dosing guidance for any compound, and all vials referenced are research-grade reagents not intended for human consumption.
How much bac water do I add to a 10 mg vial?
The volume is your choice, and it changes only the concentration. The milligrams in the vial stay the same. More water means a weaker solution and a larger draw for the same amount; less water means a stronger solution and a smaller draw, where a one-unit misread costs more.
For a 10 mg vial:
| Diluent added | Concentration | mcg per unit | 250 mcg | 500 mcg | 1 mg |
|---|---|---|---|---|---|
| 1 mL | 10 mg/mL | 100 | 2.5 units | 5 units | 10 units |
| 2 mL | 5 mg/mL | 50 | 5 units | 10 units | 20 units |
| 2.5 mL | 4 mg/mL | 40 | 6.25 units | 12.5 units | 25 units |
| 3 mL | 3.33 mg/mL | 33.3 | 7.5 units | 15 units | 30 units |
The 2 mL row is the one people want, because it gives round numbers. A September r/Biohackers thread asked exactly this (10 mg, 2 mL, 250 mcg), and the poster's complaint was the tools, not the math: "There are so many calculators out there, it's super confusing." The math is the one line above. If two calculators disagree, one of them has a unit error.
Two practical limits narrow the choice. The vial has a physical capacity (check its stated volume), so the largest volume you can add is fixed by the glass. And if your target draw lands under 2 units, small reading errors become a large share of the amount, which is why compounding references prefer dilutions that put measured volumes well inside the syringe scale.
How do I read units on a U-100 insulin syringe?
"U-100" describes the scale, not the barrel size. Every U-100 syringe is marked for 100 units per millilitre, so one unit is always 0.01 mL.
| Syringe | Capacity | Units | Typical marks |
|---|---|---|---|
| 0.3 mL | 0.3 mL | 30 | every 1 unit, some with half-unit marks |
| 0.5 mL | 0.5 mL | 50 | every 1 unit |
| 1 mL | 1 mL | 100 | every 1 or 2 units, depending on the maker |
The unit is a volume, not an amount of drug. "10 units" means 0.1 mL. How much peptide that 0.1 mL holds depends entirely on how you mixed the vial. This is why a "dose in units" copied from someone else's post is meaningless unless you also know their vial size and diluent volume.
The conversion chain, step by step:
- Concentration (mg/mL) = vial mg ÷ diluent mL
- Amount per unit (mg) = concentration ÷ 100
- Units for a target amount = target mg ÷ amount per unit
- Volume in mL = units ÷ 100
Write micrograms and milligrams carefully: 1 mg = 1,000 mcg. A common error in community threads is a factor of 10 or 1,000 lost between those two units.
Worked examples for the vial sizes people ask about
These come from questions posted on Reddit between August and September 2026. Each row is arithmetic only.
| Vial | Diluent | Concentration | Per unit | Source of the question |
|---|---|---|---|---|
| 5 mg | 1 mL | 5 mg/mL | 50 mcg | r/SemaglutideCompound |
| 5 mg | 2 mL | 2.5 mg/mL | 25 mcg | same thread |
| 10 mg | 2 mL | 5 mg/mL | 50 mcg | r/Biohackers |
| 60 mg | 2 mL | 30 mg/mL | 300 mcg | r/Peptides |
| 60 mg | 3 mL | 20 mg/mL | 200 mcg | same thread |
| 100 mg | 3 mL | 33.3 mg/mL | 333 mcg | r/Peptides |
| 600 mg | 6 mL | 100 mg/mL | 1 mg | r/Peptides |
| 1,000 mg | 10 mL | 100 mg/mL | 1 mg | r/Biohackers |
Three of these deserve a note.
60 mg with a 10 mL bottle. The poster's 60 mg vial "came with a 10 ml bottle of BAC." The bottle size is not an instruction. A 30 mL or 10 mL bac water vial is a supply for several reconstitutions, and you add only what the peptide vial holds. At 20 to 30 mg/mL each unit carries 200 to 300 mcg, so a one-unit misread is a large error. That is the trade-off of high-milligram vials.
100 mg in a vial that "only fits 3 ml". 100 ÷ 3 gives 33.33 mg/mL, a repeating decimal. The math still works; it just rounds. If you want round numbers, 2 mL gives 50 mg/mL (500 mcg per unit), at the cost of a stronger solution.
1,000 mg NAD+ and 600 mg glutathione. These are not peptides in the usual sense, and the amounts are measured in milligrams per draw, not micrograms. A 1 mL syringe at 100 mg/mL holds 100 mg at full barrel. Gram quantities usually ship in larger vials; confirm the vial's nominal volume before adding 10 mL to it.
For retatrutide vial sizes specifically, our retatrutide reconstitution page works through 5, 10 and 20 mg vials.
What diluent do compounding references use?
Bacteriostatic water for injection is sterile water with 0.9% benzyl alcohol (some products use 1.1%) as a preservative. The Hospira label on DailyMed describes it as a multiple-dose product "from which repeated withdrawals may be made to dilute or dissolve drugs for injection," with a pH of 5.7 (range 4.5 to 7.0).
Sterile water for injection has no preservative. Once punctured it is a single-use product. Some peptides dissolve poorly in plain water at neutral pH and need a dilute acetic acid solution instead; our cloudy vial troubleshooting page covers which ones and what a failed dissolution looks like.
Supply, shelf life and FDA's August position on bac water sold next to peptides are covered on our bacteriostatic water page.
How long is a reconstituted vial usable?
Two clocks run at once. The shorter one decides.
The preservative clock: 28 days. ASHP's beyond-use-date guide says an opened multiple-dose vial can be kept for 28 days unless the manufacturer's information is more conservative. That limit comes from USP preservative-effectiveness testing, and it applies to the bac water bottle and to any vial you mix with it.
The peptide clock: usually unknown. Approved peptide drugs carry stability data in their labels. Research peptides almost never do. The 14 to 30 day refrigerated window quoted across vendor sites is a convention, not a measured result for each compound. Where a community group has tested degradation, as with the retatrutide stability numbers posted in September 2026, read the method before trusting the figure.
What pharmacy practice does to protect both clocks: refrigerate at 2 to 8°C, protect from light, label the vial with the mix date and concentration, and discard at the shorter limit. Freezing single-use aliquots avoids repeated freeze-thaw cycles, which damage many peptides.
Can I mix several peptides in one vial?
A r/Peptides poster asked whether a BPC-157, GHK-Cu, CJC-1295 and ipamorelin blend could go into one vial or whether they would "degrade eachother". The honest answer is that nobody has published stability data for most of these combinations, so the question cannot be settled from the literature.
The arithmetic changes when you combine. Each component's concentration becomes its own milligrams divided by the total volume. Mix a 10 mg vial of A and a 5 mg vial of B in 3 mL total and you get 3.33 mg/mL of A and 1.67 mg/mL of B in every unit. You cannot change that ratio afterwards.
Regulators treat premixed blends as products in their own right. FDA's Royal Peptides letter lists "BIMORELIN", a tesamorelin 10 mg and ipamorelin 3 mg blend, as an unapproved new drug. For the BPC-157 and TB-500 pairing specifically, see our BPC-157 and TB-500 stack read.
Is there a printable peptide reconstitution chart?
The table below is the chart. It shows micrograms per U-100 unit for common vial sizes and diluent volumes. Print the page or save it as PDF from your browser.
| Vial ↓ / diluent → | 1 mL | 2 mL | 3 mL | 5 mL |
|---|---|---|---|---|
| 2 mg | 20 mcg | 10 mcg | 6.7 mcg | 4 mcg |
| 5 mg | 50 mcg | 25 mcg | 16.7 mcg | 10 mcg |
| 10 mg | 100 mcg | 50 mcg | 33.3 mcg | 20 mcg |
| 15 mg | 150 mcg | 75 mcg | 50 mcg | 30 mcg |
| 20 mg | 200 mcg | 100 mcg | 66.7 mcg | 40 mcg |
| 30 mg | 300 mcg | 150 mcg | 100 mcg | 60 mcg |
| 50 mg | 500 mcg | 250 mcg | 166.7 mcg | 100 mcg |
| 60 mg | 600 mcg | 300 mcg | 200 mcg | 120 mcg |
To get units for any amount, divide the amount in mcg by the cell value. If you prefer not to do the division, our peptide calculator runs the same formula. It links to no vendors.
Before you mix: confirm what is in the vial
The arithmetic assumes the label is right. Independent tests find vials that are underfilled, overfilled or a different compound; our analysis of 7,164 Janoshik tests shows how often. A 10 mg vial that actually holds 7 mg makes every number in the tables above 30% too high. Check the batch COA on the issuing lab's own site first; our guide to verifying a Janoshik COA walks through it.
Related reading
- Retatrutide reconstitution — vial-by-vial math for 5, 10 and 20 mg retatrutide.
- Bacteriostatic water in 2026 — supply, shelf life after opening, and FDA's August position.
- Peptide vial went cloudy — dissolution failures, acetic water, freeze-thaw damage.
- BPC-157 and TB-500 stack — what the evidence says about the most common two-peptide blend.
- Retatrutide dosing protocols — the dose steps the TRIUMPH trials used.
Frequently asked
How much bac water do I add to a 10 mg vial?
The volume you add changes only the concentration, not the amount of peptide. 1 mL gives 10 mg/mL (100 mcg per unit), 2 mL gives 5 mg/mL (50 mcg per unit) and 3 mL gives 3.33 mg/mL (33.3 mcg per unit). Pick a volume that keeps your target draw between 5 and 50 units, where syringe marks are easiest to read.
If I have 10 mg of a peptide and use 2 mL of bacteriostatic water, how many units is 250 mcg?
Five units. 10 mg in 2 mL is 5 mg/mL, or 5,000 mcg per mL. One unit on a U-100 syringe is 0.01 mL, so each unit holds 50 mcg. 250 mcg divided by 50 mcg per unit is 5 units. The same vial puts 500 mcg in 10 units and 1 mg in 20 units.
For 1000 mg of NAD+, do I add 10 mL?
Adding 10 mL to 1,000 mg gives 100 mg/mL, so each U-100 unit holds 1 mg and a full 1 mL syringe holds 100 mg. Whether 10 mL fits depends on the vial's physical capacity, not the label. Check the vial's nominal volume first. If it holds less, use less diluent and recalculate the concentration.
How do I read units on a U-100 insulin syringe?
U-100 means the barrel is scaled for 100 units per millilitre, so 1 unit equals 0.01 mL whatever the syringe size. A 0.3 mL syringe holds 30 units, a 0.5 mL syringe 50 units and a 1 mL syringe 100 units. Smaller barrels have wider spacing between marks, which makes small volumes easier to read.
Can I mix several peptides in one vial?
You can do the arithmetic, but no published stability data exist for most research-peptide blends. Each peptide's concentration becomes its own milligrams divided by the total volume, and the ratio between them is fixed once mixed. FDA's August 2026 letter to Royal Peptides cited a premixed tesamorelin and ipamorelin blend as an unapproved drug.
How long does a reconstituted peptide last in the refrigerator?
Two limits apply, and the shorter one wins. Pharmacy guidance caps an opened multiple-dose vial at 28 days because the preservative's protection is only validated that long. Peptide stability is the second limit, and for most research peptides no published refrigerated-stability study exists. Vendor claims of 30 to 60 days are not evidence.