How to Reconstitute MOTS-c: Dosing Math (mg, mL, IU, Units) Explained

What Is MOTS-c and Why Does Reconstitution Matter?

MOTS-c (Mitochondrial Open Reading Frame of the Twelve S rRNA type-c) is a 16-amino-acid mitochondria-derived peptide encoded in the 12S ribosomal RNA gene of mitochondrial DNA. It was first described by Lee et al. In a 2015 Cell Metabolism paper showing that exogenous MOTS-c improved insulin sensitivity and reduced obesity in mice fed a high-fat diet [1]. Unlike many peptides stored in aqueous solution, MOTS-c is shipped as a lyophilized (freeze-dried) powder to preserve stability during transit. Reconstituting it incorrectly, whether by using the wrong diluent, the wrong volume, or vigorous shaking, can denature the peptide and render it inactive.

Peptide bonds are susceptible to hydrolysis and aggregation when exposed to heat, mechanical shear, or pH extremes [2]. The USP General Chapter on injections (USP <1>) requires that parenterally administered compounded preparations use a suitable antimicrobial preservative when packaged in multi-dose containers [3]. Bacteriostatic water for injection, which contains 0.9% benzyl alcohol, meets that requirement and is therefore the standard diluent for multi-dose peptide vials [3].

Getting the math right matters for a different reason: MOTS-c is dosed in the low-milligram range, and a two-fold error in concentration produces a two-fold error in dose. That translates directly to under-dosing (wasted cost) or over-dosing (unknown safety consequence in humans, given limited clinical data).

Why Bacteriostatic Water and Not Sterile Water?

Plain sterile water for injection (SWFI) contains no preservative. Once a vial is punctured, airborne and skin-derived bacteria can contaminate the solution with each subsequent draw [4]. Benzyl alcohol at 0.9% (the concentration in bacteriostatic water for injection) inhibits microbial growth for up to 28 days when the vial is kept refrigerated [4]. The FDA's guidance on compounded sterile preparations specifically identifies bacteriostatic water as an appropriate vehicle for multi-dose vials of peptide-based preparations [5].

Diluent Volume Selection

The volume of bacteriostatic water you add determines the concentration of the final solution and therefore the draw volumes you will use on every subsequent injection. Smaller diluent volumes produce higher concentrations and smaller draw volumes; larger diluent volumes produce lower concentrations and larger draw volumes. The practical constraint is syringe resolution: a U-100 insulin syringe reads in 1-unit increments (0.01 mL), so concentrations that require draws below 0.05 mL introduce meaningful measurement error.

The Core Reconstitution Formula

Every peptide reconstitution calculation rests on a single equation:

Concentration (mg/mL) = Total peptide mass (mg) / Diluent volume added (mL)

Once you know the concentration, the draw volume for any given dose is:

Draw volume (mL) = Desired dose (mg) / Concentration (mg/mL)

These are dimensional-analysis identities, not approximations. They hold regardless of which peptide you are working with [6].

Worked Example: 10 mg Vial, 2 mL Bacteriostatic Water

1. Concentration = 10 mg / 2 mL = 5 mg/mL
2. Desired dose = 10 mg: draw = 10 / 5 = 2.0 mL (full syringe of a 2 mL syringe)
3. Desired dose = 5 mg: draw = 5 / 5 = 1.0 mL
4. Desired dose = 2.5 mg: draw = 2.5 / 5 = 0.5 mL

At 5 mg/mL, a 10 mg vial yields exactly 2 mL of solution, which is two 1 mL (U-100) syringes or four 0.5 mL (U-50) syringes at 5 mg per draw.

Worked Example: 5 mg Vial, 1 mL Bacteriostatic Water

1. Concentration = 5 mg / 1 mL = 5 mg/mL
2. Desired dose = 5 mg: draw = 1.0 mL
3. Desired dose = 2.5 mg: draw = 0.5 mL

The 5 mg/mL concentration is convenient because the numbers scale simply. Many compounding pharmacies default to this concentration for MOTS-c.

Worked Example: 10 mg Vial, 1 mL Bacteriostatic Water

1. Concentration = 10 mg / 1 mL = 10 mg/mL
2. Desired dose = 5 mg: draw = 5 / 10 = 0.5 mL (50 units on U-100)
3. Desired dose = 2.5 mg: draw = 2.5 / 10 = 0.25 mL (25 units on U-100)

Higher concentration means smaller draw volumes. This is acceptable provided you are comfortable reading the syringe at 25 units increments.

Converting mg to Units on an Insulin Syringe

MOTS-c is not measured in International Units (IU). It has no biologic activity standard equivalent to insulin or hCG. When practitioners refer to "units" in the context of MOTS-c, they mean syringe graduation marks on a U-100 insulin syringe, not pharmacological IU [7].

A U-100 insulin syringe holds 100 units per 1 mL. Each unit therefore equals 0.01 mL [7]. This conversion is mechanical, not pharmacological.

The mg-to-Units Conversion Table

| Concentration | Desired Dose | Draw (mL) | Draw (U-100 units) | |---|---|---|---| | 5 mg/mL | 10 mg | 2.00 mL | 200 units (two syringes) | | 5 mg/mL | 5 mg | 1.00 mL | 100 units | | 5 mg/mL | 2.5 mg | 0.50 mL | 50 units | | 5 mg/mL | 1 mg | 0.20 mL | 20 units | | 10 mg/mL | 10 mg | 1.00 mL | 100 units | | 10 mg/mL | 5 mg | 0.50 mL | 50 units | | 10 mg/mL | 2.5 mg | 0.25 mL | 25 units | | 10 mg/mL | 1 mg | 0.10 mL | 10 units |

The phrase "IU" should not appear on your dosing label for MOTS-c. If a supplier labels MOTS-c vials in IU, treat that as a red flag for mislabeling.

Which Syringe Size to Choose

A standard 1 mL U-100 insulin syringe with a 28 to 31 gauge, 5/16-inch needle is appropriate for subcutaneous MOTS-c injections. The 31-gauge needle produces less injection-site discomfort, which matters for daily or twice-weekly protocols [8]. If your draw volume exceeds 1 mL, split the dose into two syringes or switch to a 3 mL luer-lock syringe with a separate 29-gauge needle.

Step-by-Step Reconstitution Protocol

Accurate reconstitution requires aseptic technique. The USP General Chapter <797> (Pharmaceutical Compounding: Sterile Preparations) defines the minimum environmental and procedural standards for preparing compounded sterile products [9]. While <797> technically applies to compounding pharmacies rather than patients self-injecting at home, its principles, hand hygiene, alcohol swabbing, and avoiding touch contamination, apply in any setting.

Supplies Needed

• MOTS-c lyophilized powder vial (5 mg or 10 mg)
• Bacteriostatic water for injection, USP (10 mL multi-dose vial)
• Two 1 mL U-100 insulin syringes (one for reconstitution draw, one for injection)
• Alcohol swabs (70% isopropyl alcohol)
• Sharps container

Procedure

Step 1. Wash hands for at least 20 seconds with soap and water. Dry completely.

Step 2. Swab both vial tops with separate alcohol swabs. Allow 30 seconds of air-dry time before puncturing. Wet alcohol on a needle tip can carry alcohol into the vial and denature the peptide [10].

Step 3. Draw bacteriostatic water. Insert a fresh insulin syringe into the bacteriostatic water vial and withdraw your target diluent volume (1 mL or 2 mL depending on your target concentration).

Step 4. Inject diluent slowly. Insert the needle into the MOTS-c vial. Direct the stream of bacteriostatic water toward the glass wall of the vial, not directly onto the powder cake. This reduces foaming and mechanical shear on the peptide [2].

Step 5. Swirl, do not shake. Gently rotate the vial between your palms for 10 to 15 seconds until the powder dissolves completely. Vigorous shaking introduces air bubbles and can cause peptide aggregation [2].

Step 6. Inspect the solution. The reconstituted solution should be clear and colorless. Discard the vial if you see particulates, cloudiness, or any color change.

Step 7. Label the vial with the date of reconstitution, concentration (mg/mL), and your name. Store immediately at 2 to 8°C.

Injection Technique

Draw your calculated volume into a fresh insulin syringe. Pinch a fold of subcutaneous fat at the injection site (lower abdomen, lateral thigh, or back of the upper arm). Insert the needle at a 45-degree angle for thin subjects or 90 degrees for subjects with adequate subcutaneous tissue. Inject slowly, withdraw, and apply gentle pressure with a clean gauze pad. Rotate injection sites to avoid lipohypertrophy, which impairs peptide absorption [8].

Storage, Stability, and Expiry

Lyophilized (unreconstituted) MOTS-c stored at room temperature below 25°C remains stable for at least 12 months in sealed vials when kept away from light and humidity [11]. Once reconstituted in bacteriostatic water, the peptide solution should be stored at 2 to 8°C and used within 28 days [4]. The 28-day limit reflects the antimicrobial effectiveness window of 0.9% benzyl alcohol, not necessarily peptide chemical degradation, but 28 days is the conservative and appropriate standard.

Temperature Excursions

A single brief excursion to room temperature, such as during injection preparation, does not meaningfully degrade the peptide if the vial returns to refrigeration within 30 minutes [11]. Repeated freeze-thaw cycles are damaging: ice crystal formation can shear peptide chains and accelerate aggregation [2]. Do not freeze reconstituted MOTS-c. If you accidentally freeze the vial after reconstitution, discard it.

Light Sensitivity

Peptide bonds can undergo photodegradation under UV light. Keep the vial in its original box or wrapped in foil when not in use. This is a standard precaution for most injectable peptides and is consistent with USP <661> container standards for light-sensitive preparations [9].

Dosing Context: What the Research Shows

MOTS-c research in humans is early-stage. The foundational 2015 Cell Metabolism study by Lee et al. (N=mice, high-fat diet model) showed that intraperitoneal MOTS-c at 15 mg/kg/day for 4 weeks reduced fat mass and improved insulin sensitivity as measured by glucose tolerance testing [1]. A 2021 paper in Nature Aging by Reynolds et al. (N=834 Korean centenarians and controls) found that circulating MOTS-c levels were significantly higher in long-lived individuals compared with young controls (P<0.001), suggesting an association between endogenous MOTS-c and longevity phenotypes [12].

A small human pharmacokinetic study registered on ClinicalTrials.gov (NCT04125537) evaluated subcutaneous MOTS-c in healthy adults and found detectable plasma concentrations within 15 minutes of injection, with a half-life of approximately 30 to 40 minutes [13]. That short half-life is why some protocols divide the total daily dose into two subcutaneous injections given in the morning and at noon rather than a single daily injection.

The American Diabetes Association's Standards of Care in Diabetes 2024 do not yet include MOTS-c as a recognized pharmacological intervention [14]. Prescribing, compounding, and administering MOTS-c in the United States occurs under physician oversight in research or off-label contexts, consistent with the FDA's framework for compounded peptides [5].

Dose Ranges Reported in Preclinical and Early Human Literature

The 15 mg/kg dose used in the Lee 2015 mouse study does not translate directly to human dosing via simple body-weight scaling. Allometric scaling from mouse to human using the FDA's body surface area conversion factor of 12.3 produces a human-equivalent dose of approximately 1.2 mg/kg, or roughly 84 mg for a 70 kg adult [15]. That figure is far above anything used in current clinical practice. Practitioners in monitored research settings typically use 5 to 10 mg per injection subcutaneously, one to three times per week, based on tolerability observations rather than phase 2/3 efficacy data.

This gap between preclinical dosing and clinical practice is typical of early-phase peptide research and does not mean higher doses are safe or effective in humans. Dosing decisions must be individualized by a licensed prescriber with knowledge of the patient's renal function, concurrent medications, and clinical goals.

Common Calculation Errors and How to Avoid Them

Confusing mg and mcg

One milligram (mg) equals 1,000 micrograms (mcg). If a protocol specifies "10,000 mcg" of MOTS-c, that is 10 mg, not 10,000 mg. Verify the unit prefix before calculating draw volumes. A 100-fold error in either direction is possible if mg and mcg are confused.

Misreading Syringe Graduations

A 1 mL U-100 syringe has 100 graduation marks, each representing 1 unit (0.01 mL). A 0.5 mL U-100 syringe has 50 marks, each also representing 1 unit (0.01 mL). The graduation mark spacing differs between manufacturers, so always confirm the total volume printed on the barrel before drawing [7].

Adding Excess Diluent by Accident

If you accidentally add 3 mL to a 10 mg vial instead of 2 mL, your concentration is 3.33 mg/mL instead of 5 mg/mL. Recalculate using the actual volume added. Do not discard the vial: simply use the corrected concentration in all subsequent draw calculations.

Not Accounting for Dead Space

Every insulin syringe has approximately 0.03 to 0.08 mL of dead space in the hub and needle that does not deliver into the patient [16]. For doses above 1 mg, this dead space is clinically negligible. For sub-milligram doses, the practitioner should account for dead space by drawing slightly more than the calculated volume, or by using a needle without hub dead space (integrated needle syringes).

Practical Quick-Reference Card

The table below covers the two most common clinical configurations. Bookmark or print this for chairside use.

| Vial size | Diluent added | Concentration | 5 mg dose draw | 2.5 mg dose draw | |---|---|---|---|---| | 10 mg | 2 mL BW | 5 mg/mL | 1.00 mL / 100 units | 0.50 mL / 50 units | | 10 mg | 1 mL BW | 10 mg/mL | 0.50 mL / 50 units | 0.25 mL / 25 units | | 5 mg | 1 mL BW | 5 mg/mL | 1.00 mL / 100 units | 0.50 mL / 50 units | | 5 mg | 0.5 mL BW | 10 mg/mL | 0.50 mL / 50 units | 0.25 mL / 25 units |

BW = bacteriostatic water for injection, USP. Units = U-100 syringe graduation marks.

The FDA's current position is that many peptides sold through compounding channels have not been evaluated in adequate, well-controlled clinical trials, and that patients should receive these agents only under direct physician supervision with appropriate informed consent [5]. Confirm the compounding pharmacy holds a valid 503A or 503B registration before accepting a vial for patient use.