Peptide Dose Math, Explained: mg, mL, and Units

For research and educational purposes only. All compounds discussed on AethonLabs.ca are sold strictly for research use and are not intended for human consumption. Always consult a qualified healthcare professional before beginning any new protocol.

Last updated: July 2026

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Every dose calculation in peptide research comes down to the same handful of steps, regardless of which compound you’re working with. This page starts from the actual units involved — what they are, and why converting between them is necessary in the first place — before building up to the formula and a few worked examples. The goal isn’t to give you a lookup table. It’s for you to finish this page able to work out any dose, for any compound, on your own.

The Three Units You’re Actually Working With

Before any formula makes sense, it helps to be clear that you’re dealing with three genuinely different kinds of measurement, not three names for the same thing.

Milligrams (mg) measure mass — how much actual compound you have. When a vial says “10mg,” that’s telling you the weight of the peptide powder inside it, before anything else is added. This number never changes based on how you reconstitute the vial — a 10mg vial contains 10mg of compound whether you add 1mL of water or 3mL.

Millilitres (mL) measure volume — how much liquid there is. When you add “2mL of BAC water” to a vial, you’re adding two millilitres of liquid. This is a completely separate quantity from the mg figure above — it’s describing the water, not the compound dissolved in it.

Units are a syringe-specific measurement of volume, not a universal one. This is the one that trips people up, because “units” sounds like it should be its own kind of thing, but it isn’t — it’s just a different, finer way of marking volume, specific to the syringe you’re using. A standard U-100 insulin syringe is calibrated so that 100 units = 1 millilitre. That “U-100” isn’t a brand name, it’s a standard — it tells you the syringe’s entire barrel of 100 units holds exactly 1mL. So one unit is always 1/100th of a millilitre, or 0.01mL, on this type of syringe, regardless of what’s in the syringe.

The reason a calculation is needed at all is that your dose is expressed in mg (mass), but what you actually control with a syringe is mL or units (volume). Those two things aren’t directly convertible on their own — you need one more piece of information to bridge them.

The Bridge: Concentration

That missing piece is concentration — how much mass is packed into each unit of volume, expressed as mg/mL. This is the number that actually connects the mass you want to deliver to the volume you need to draw, and it’s the direct result of how you reconstituted the vial:

Concentration (mg/mL) = Total peptide in the vial (mg) ÷ Volume of liquid added (mL)

A 10mg vial with 1mL of BAC water added gives you 10mg/mL. The same 10mg vial with 2mL added instead gives you 5mg/mL — the amount of compound hasn’t changed, only how spread out it is in the liquid. This is worth sitting with, because it’s the entire reason reconstitution volume matters: it’s the choice that sets your concentration, and your concentration is what determines every dose calculation you’ll do from that vial afterward.

The Core Formula

Once you know your concentration, you can find the volume needed for any target dose:

Volume to draw (mL) = Desired dose (mg) ÷ Concentration (mg/mL)

And since 100 units = 1mL on a standard syringe, converting that volume to units just means multiplying by 100:

Units to draw = [Desired dose (mg) ÷ Concentration (mg/mL)] × 100

That’s the whole method. Everything else on this page is either background that makes this formula make sense, or examples applying it.

What Changes at Different Concentrations

How much liquid you add changes your concentration, which changes how many units any given dose works out to. A typical peptide vial holds about 3mL total, so that’s usually the ceiling you’re working within when choosing how much BAC water to add — NAD+ is the main exception in our catalog, typically supplied in larger 10mL vials given its much bigger per-dose amounts.

Concentration	1 unit =	Example dose	Units to draw
10mg/mL	100mcg	1mg	10 units
5mg/mL	50mcg	1mg	20 units
2.5mg/mL	25mcg	250mcg	10 units
1mg/mL	10mcg	100mcg	10 units

Less diluting liquid means a higher concentration and fewer units per dose — more convenient for larger doses, but coarser precision for small ones. More liquid means a lower concentration, more units per dose, and finer precision, at the cost of a bigger injection volume. Neither is universally right; it depends on your dose.

Finding Your Concentration After Reconstitution

In practice, this is the very first calculation you’ll do with any new vial, and it only requires two numbers you already have: the mg amount printed on the vial, and the mL of liquid you added.

Say you have a 20mg vial and you add 2mL of BAC water. Concentration = 20mg ÷ 2mL = 10mg/mL. That single number is now true for that entire vial until it’s empty — every future dose calculation from it starts here. This is exactly why recording your reconstitution volume the moment you prepare a vial matters so much: if you forget how much liquid you added, there’s no way to reliably work backward to your concentration later.

Worked Examples

These build from simple to slightly more involved. Try covering the answer and working through the formula yourself before reading it — that’s the actual test of whether the concept has landed.

Example 1. You reconstitute a 10mg vial with 1mL of BAC water, giving 10mg/mL. Your target dose is 1mg. Volume = 1mg ÷ 10mg/mL = 0.1mL. Units = 0.1mL × 100 = 10 units.

Example 2. You reconstitute a 20mg vial with 1mL of BAC water, giving 20mg/mL. Your target dose is 4mg. Volume = 4mg ÷ 20mg/mL = 0.2mL. Units = 0.2mL × 100 = 20 units.

Example 3 — a small microgram dose. You reconstitute a 5mg vial with 2mL of BAC water, giving 2.5mg/mL. Your target dose is 250mcg. The formula only works in consistent units, so convert first: 250mcg = 0.25mg. Volume = 0.25mg ÷ 2.5mg/mL = 0.1mL. Units = 0.1mL × 100 = 10 units. Forgetting this conversion step — treating 250mcg as if it were 250mg — is one of the most common arithmetic mistakes in this entire process, and it produces an answer wrong by a factor of 1,000.

Example 4 — a combined blend dose. You reconstitute a 10mg total vial (5mg of Compound A plus 5mg of Compound B, blended 1:1) with 2mL of BAC water, giving 5mg/mL combined, or 2.5mg/mL of each individual compound. Your target is 250mcg of each. Volume = 0.25mg ÷ 2.5mg/mL = 0.1mL. Units = 10 units — which delivers 250mcg of each compound at the same time. The thing to watch with any blend: confirm whether a quoted “dose” means the combined total or the amount of each individual compound, and confirm the actual ratio your specific product uses before you calculate — ratios vary between vendors.

How to Choose Your Reconstitution Volume

If you’re deciding whether to dilute more or less than whatever a vendor or guide suggests as a default, here’s the actual decision logic:

Choose a more concentrated reconstitution (less liquid) if:

• You’re at a higher dose and want to avoid an excessively large injection volume
• You’re comfortable with the resulting unit increments and don’t need extra precision

Choose a more dilute reconstitution (more liquid) if:

• You’re at a very low dose — common during early titration phases, or with compounds dosed in single-digit micrograms — and want more syringe travel for measurement precision
• You’re newer to drawing peptide doses and want more margin for small measurement errors

There’s no universally “correct” choice here. Both directions are valid as long as your math is consistent and your final draw is accurate. Community practice tends to converge on certain splits for certain compounds — those are covered in each compound’s own guide — but you’re not locked into them if a different volume suits your specific dose better.

A Word on Vial Size vs. Stability Window

Choosing a reconstitution volume isn’t only about the math above — it’s also about matching your vial to how long you’ll actually be using it. A vial reconstituted for a dose you’ll be taking over many weeks may outlast its roughly 28-day stability window before you finish it. Our storage guide covers this in more depth — it’s worth factoring in alongside the concentration math, particularly for a low, slowly-titrating dose that will draw a vial out over a long period.

Common Mistakes in Dose Math

• Confusing micrograms and milligrams. This is the single most common error across every compound dosed in mcg — 250mcg is 0.25mg, not 250mg. Convert before you calculate, every time, even if you’ve done it a hundred times before.
• Assuming a blend’s “dose” figure means an equal split. Blend ratios are frequently uneven (some skew heavily toward one component), so a combined-dose figure doesn’t tell you what’s actually being delivered per compound unless you know the specific ratio.
• Forgetting the reconstitution volume you actually used. If you can’t remember exactly how much liquid you added, you cannot reliably calculate a dose from that vial — record it the moment you reconstitute, not from memory later.
• Applying one compound’s standard concentration to a different vial size without recalculating. The formula is the same every time, but the numbers going into it change with every new vial, even for the same compound.
• Not double-checking a draw that looks unusually large or small. If your calculated volume feels surprising for the dose you’re targeting, that’s almost always a sign of a math error, not a coincidence — recheck before drawing.

Common Questions

Is there a “correct” concentration I should always reconstitute to? No single concentration is correct for every situation — it depends on your specific dose and how much precision or injection volume you’re comfortable with. Each compound’s own guide lists the concentrations most commonly used in community practice as a starting reference point.

Why do some compounds get reconstituted with acetic acid instead of BAC water? A small number of compounds are more chemically stable in a mildly acidic environment and can degrade or fail to dissolve properly in standard bacteriostatic water. This is genuinely compound-specific — most peptides in our catalog reconstitute normally with BAC water, and only a few exceptions require acetic acid. Always check the specific compound’s own guide rather than assuming either way.

What if my dose falls between two clean unit numbers? This usually means it’s worth reconsidering your reconstitution volume rather than drawing an awkward fractional unit repeatedly — a different concentration will often turn an ugly number into a clean one for your specific dose.

Does this math change for intramuscular versus subcutaneous injection? No — the underlying formula for converting a dose to a volume is identical regardless of route. What changes with route is needle length and injection technique, not the concentration math.

Where to Go From Here

• Every compound guide in this library includes its own worked dose math and standard reconstitution reference for that specific compound
• Our Reconstitution Guide
• Our Storage Guide
• Our Sterile Injection Technique Guide
• Our Syringes, Needles, and Supplies Guide

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This guide reflects general dose calculation methodology and will be updated periodically. It is provided for research and educational purposes only and does not constitute medical advice. AethonLabs.ca sells all compounds strictly for research use; products are not intended for human consumption. Consult a qualified healthcare professional before beginning any new protocol.

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