Dosing math

Peptide arithmetic uses four units, and errors almost always trace back to mixing them.

Milligrams (mg) are the standard unit for the lyophilised powder. Research peptides are typically supplied in vials of 2mg to 30mg. The figure on the label is the mass of active compound, not the mass of the reconstituted solution.

Micrograms (mcg) are the working unit for most peptide doses because effective quantities are small. The governing conversion is 1mg = 1000mcg. Every mg figure on a vial should be converted to mcg before it is compared with a dose written in mcg; doing the conversion explicitly rather than mentally is what prevents the 1000x error.

Millilitres (mL) measure liquid volume, principally the bacteriostatic water used for reconstitution. Standard syringes are graduated in mL. Insulin syringes are graduated in units, with 100 units = 1mL, so unit readings are simply mL × 100.

International Units (IU) apply to compounds such as growth hormone and HCG. An IU is defined per compound by biological activity, so IU values are not interchangeable between peptides and there is no universal IU-to-mass factor. Operationally, IU behaves like mg or mcg within a single compound: concentration in IU/mL and injection volume in mL follow the same formulas, without cross-compound conversion.

The practical discipline is to state the unit of the vial contents, the unit of the intended dose, and the graduation of the syringe before any division is performed. Where the vial is in mg and the dose in mcg, the conversion happens first and is written down. The rest of the calculation is straightforward once the units are aligned.

Concentration is the central quantity in reconstitution arithmetic: the mass of compound per unit volume of solution. A fixed mass of lyophilised peptide dissolved in a chosen volume of bacteriostatic water yields a solution whose strength is entirely determined by that volume.

The coffee analogy holds exactly. Espresso is high concentration (a given mass of grounds in a small volume); an americano is the same mass in a larger volume, hence lower concentration. Total compound is unchanged; only the mass delivered per millilitre differs.

The formula: Concentration = Weight ÷ Volume

Worked example: 10mg of MT-2 reconstituted with 2mL of bacteriostatic water.

• Concentration = 10mg ÷ 2mL = 5mg/mL
• Each millilitre contains 5mg of MT-2

Since doses are generally expressed in mcg, the concentration is converted by multiplying the mg figure by 1000: 5mg/mL = 5000mcg/mL. Carrying the concentration in mcg/mL from this point avoids a unit conversion at the injection-volume step, which is where mg/mcg confusion typically occurs.

The relationship is inverse: increasing reconstitution volume lowers concentration and increases the draw volume required for a given dose; decreasing it does the opposite. This is why the reconstitution volume is a planning decision rather than an afterthought, and why any change to it requires recalculating every downstream draw.

In practice the concentration in mcg/mL (or IU/mL) is recorded on the vial at reconstitution. Every subsequent injection volume is derived from that one figure, so it is the number that must be unambiguous.

The complete calculation, using BPC-157 as the worked example. The structure is identical for any compound.

Given:

• Drug: BPC-157
• Vial contains: 5mg
• Desired dose: 250mcg
• Reconstitution volume: 2mL bacteriostatic water

Step 1: Concentration.

• Concentration = 5mg ÷ 2mL = 2.5mg/mL
• Convert to mcg: 2.5mg/mL × 1000 = 2500mcg/mL

The conversion to mcg/mL is performed here so that the next step divides like units by like units.

Step 2: Injection volume.

• Formula: Injection volume = Desired dose ÷ Concentration
• Injection volume = 250mcg ÷ 2500mcg/mL = 0.1mL

Dimensional analysis confirms the result: mcg divided by mcg/mL leaves mL. If the units do not cancel to mL, a conversion has been missed.

Step 3: Syringe graduation.

• Insulin syringe: 0.1mL = 10 units
• Standard syringe: 0.1mL (one small line past the 0.05mL mark)

The method generalises directly: concentration from vial mass and reconstitution volume, volume from dose and concentration, then a graduation conversion determined by the syringe in hand. The only precondition is unit agreement between dose and concentration before division. For IU-dosed compounds the same steps apply with IU replacing mcg throughout.

The 250mcg dose is illustrative of the arithmetic, not a recommendation; compound pages carry the actual protocols. In practice the three lines are written out in full for each new vial or dose change rather than performed mentally, since the written form exposes a dropped factor of 1000 immediately.

Three further examples applying the identical structure. The doses illustrate the arithmetic only; compound pages carry the actual protocols.

Example 1: Semaglutide

• Vial: 5mg, reconstituted with: 2mL, desired dose: 250mcg
• Concentration: 5mg ÷ 2mL = 2.5mg/mL = 2500mcg/mL
• Injection volume: 250mcg ÷ 2500mcg/mL = 0.1mL = 10 units

Example 2: CJC-1295

• Vial: 2mg, reconstituted with: 2mL, desired dose: 100mcg
• Concentration: 2mg ÷ 2mL = 1mg/mL = 1000mcg/mL
• Injection volume: 100mcg ÷ 1000mcg/mL = 0.1mL = 10 units

Examples 1 and 2 both resolve to 10 units despite differing doses, because the smaller vial mass at the same reconstitution volume yields proportionally lower concentration. Draw volume is a function of dose and concentration jointly; a familiar unit reading on the syringe is not evidence that the dose is correct if the vial or water volume has changed.

Example 3: Growth hormone (using IU)

• Vial: 10IU, reconstituted with: 1mL, desired dose: 2IU
• Concentration: 10IU ÷ 1mL = 10IU/mL
• Injection volume: 2IU ÷ 10IU/mL = 0.2mL = 20 units

IU-denominated compounds follow the same two divisions with no mass conversion step, since vial content and dose share the unit. The insulin-syringe conversion (mL × 100) is unchanged.

In practice the three lines are recomputed for every new vial, since supplier vial sizes vary and a change from 5mg to 2mg at constant water volume changes the concentration by a factor of 2.5. Results outside the low tens of units for mcg-scale doses warrant a unit check before proceeding.

The final step converts a calculated volume in mL into a graduation on the syringe actually in use. Two syringe types are relevant and their scales differ.

Insulin syringes are the most common choice for peptides.

• Graduated in units from 0 to 100
• 100 units = 1mL
• Conversion is a two-place decimal shift: 0.1mL = 10 units

The unit scale gives fine resolution over a 1mL total volume, which suits the 0.05mL to 0.5mL range typical of peptide draws. Each unit corresponds to 0.01 mL, so a 10-unit draw is unambiguous and small adjustments are readable.

Standard syringes are less common for peptides.

• Graduated in mL with decimal subdivisions
• Intermediate volumes fall on the minor lines between major marks
• 0.1mL is typically one small line past the 0.05mL mark

Standard syringes are designed for larger volumes, so a given linear distance along the barrel represents more liquid. Reading 0.1mL accurately requires attention to the minor graduations, and plunger-position error translates into a larger proportional dose error than on an insulin syringe.

The critical discipline is to identify the syringe type before interpreting a mark. The numeral 10 on an insulin syringe denotes 10 units (0.1mL); a numeral on a standard syringe denotes mL directly. Confusing the two scales produces a tenfold or greater error independent of any mistake in the concentration arithmetic. In practice the calculated volume is written in both mL and units, and the syringe is read against whichever scale it carries.

Verification is a standing step, not an optional one. Three checks apply.

Always verify calculations:

1. Does the injection volume make sense? Peptide draws typically fall between 0.05mL and 0.5mL. A result well outside that band is a signal to re-examine inputs before anything else.
2. Multiply the injection volume by the concentration. The product must equal the intended dose. For the BPC-157 example: 0.1mL × 2500mcg/mL = 250mcg. Reversing the division is the most reliable single check because it is independent of the original arithmetic path.
3. When in doubt, use the dosing calculator on this site or have someone check the numbers.

Common-sense checks:

• Very small doses (mcg) correspond to very small injection volumes
• If more than 0.5mL is required, reconstituting with less water is the usual remedy
• If the calculation yields a very large injection volume, the unit conversions are the first place to look

The reverse-multiplication check exposes both arithmetic slips and unit errors: a dropped factor of 1000 in the concentration produces a product that is off by the same factor. The plausibility range catches the same error from a different angle, since a mcg-scale dose that resolves to several mL almost always indicates that concentration was left in mg/mL while the dose was in mcg.

In practice all three checks are applied to every fresh calculation regardless of how routine the numbers appear, because an incorrect result carries no visible marker of being wrong. Consistency of the check is what provides the protection.

Reconstitution volume is a design parameter that trades measurement precision against injection volume and vial longevity.

Higher concentration (less water added):

• Pros: smaller injection volumes; vials last through more draws
• Cons: less precise dosing; small doses occupy few graduations and are harder to measure accurately

Lower concentration (more water added):

• Pros: more precise dosing; small dose adjustments are easier to resolve on the syringe
• Cons: larger injection volumes; vials are exhausted faster

The underlying reason is that syringe reading error is roughly constant in absolute terms (a fraction of a graduation), so its proportional effect on dose shrinks as the draw volume grows. A dose that occupies only a few graduations carries far greater relative uncertainty than the same dose spread across many. Conversely, draws approaching the 0.5mL end of the typical range become uncomfortable and suggest the solution is too dilute for the intended dose.

Recommended approach: 1-2mL of bacteriostatic water for most peptides, which balances precision with practicality. Within that range, the choice can be tuned to the dose: lower doses favour the higher water volume, higher doses the lower.

In practice the reconstitution volume is chosen by working the calculation forward from the intended dose before any water is added, targeting a draw that sits comfortably within the insulin-syringe scale. Once reconstituted, the concentration is fixed for the life of that vial, and any later change in intended dose alters only the draw volume, not the concentration. Recording the concentration on the vial at the moment of reconstitution removes any dependence on recalling the water volume later.

Certain compounds are dosed by body mass rather than as a fixed quantity. Testosterone replacement is the usual illustration.

The milligram per kilogram method scales dose to body weight, mirroring medical dosing practice. It often works better than arbitrary dosing, particularly for beginners, because it anchors the starting dose to a physiological variable rather than convention.

General ranges for reference:

• 1mg/kg = Western medicine TRT (conservative)
• 2mg/kg = Modern TRT (standard optimisation)
• 3mg/kg = Optimised TRT (higher end)

Example calculation:

• 90kg male seeking modern TRT
• 90kg × 2mg/kg = 180mg per week
• This provides a systematic starting point rather than a guess

The arithmetic is a single multiplication of body mass in kilograms by the selected mg/kg coefficient, with the result expressed per week in this example. Body mass recorded in pounds must be converted to kilograms before multiplying, or the result is inflated by the conversion factor.

Important note: individual response varies significantly. Some men require more or less than the mg/kg calculation indicates. The figure is a protocol-development starting point to be adjusted against observed response, not a fixed target.

The weight-based result feeds into the same downstream arithmetic as any other dose: it becomes the desired dose, which is divided by the concentration of the preparation to give an injection volume, then converted to syringe graduations and verified. Compound pages carry the actual protocols; the figures here demonstrate the method only.

Four principles address the failure modes that produce serious dosing errors.

The 1000x error. Confusing mg and mcg produces a dose 1000 times too high or too low. It is the dominant risk in peptide arithmetic because the conversion is a single factor applied at one step, and omitting it leaves no visible trace in the intermediate numbers. Units are checked explicitly at every line, and concentration is carried in mcg/mL from the outset so that the division step involves like units.

When to recalculate. Any change to reconstitution volume, vial size, or desired dose requires recalculating from the beginning. Vial mass varies between suppliers, reconstitution volume determines concentration, and dose determines draw volume; no previously derived figure survives a change to any input. Treating a familiar unit reading as reusable across vials of different mass at the same water volume is a common source of error, as the CJC-1295 and semaglutide examples illustrate.

Verification methods. Online calculators, independent review by another person, or confirmation by a different calculation method. Reverse multiplication (volume × concentration = dose) is the most accessible independent route and detects both arithmetic and unit errors.

If unsure. Slight underdosing with upward adjustment is safer than accidental overdose. Starting conservatively and titrating on response bounds the consequence of any residual error to the low side, where it is correctable.

In practice these reduce to a fixed routine: label each vial with its concentration at reconstitution, write the full calculation for every new dose, apply the plausibility range and reverse check, and resolve any uncertainty toward the smaller draw. The arithmetic is elementary; the safety margin comes entirely from performing it, and the checks, without exception.