Why is sermorelin measured in mcg but injected in mL?
Sermorelin is a growth hormone-releasing peptide — a synthetic analog of the first 29 amino acids of endogenous GHRH (growth hormone-releasing hormone). It is prescribed in micrograms (mcg) because that is the biologically meaningful unit of active peptide. Syringes, however, measure volume in milliliters (mL). To inject the right amount of active peptide, you need to know the concentration of your reconstituted vial.
Compounded sermorelin is supplied as a lyophilized (freeze-dried) powder in a sealed vial. Before use, you dissolve it in bacteriostatic water. The total amount of peptide in the vial is fixed — what changes is the concentration, which is determined by how much water you add.
How do I convert my sermorelin mcg dose to mL?
Concentration (mcg/mL) = Total peptide in vial (mcg) ÷ Volume of water added (mL)
Once you know the concentration, the volume to inject is simple:
Volume to inject (mL) = Your prescribed dose (mcg) ÷ Concentration (mcg/mL)
Example: 9 mg vial + 2 mL water
A common compounded sermorelin vial contains 9 mg (9,000 mcg) of peptide. If your pharmacy instructs you to add 2 mL of bacteriostatic water, the concentration is:
9,000 mcg ÷ 2 mL = 4,500 mcg/mL
For a prescribed dose of 300 mcg:
300 mcg ÷ 4,500 mcg/mL = 0.067 mL
On a standard 1 mL insulin syringe (100 units), 0.067 mL equals approximately 6.7 units. Most patients round to 7 units for practical measurement — but confirm this with your pharmacy or clinician.
Example: 9 mg vial + 3 mL water
If instead you add 3 mL, the concentration drops:
9,000 mcg ÷ 3 mL = 3,000 mcg/mL
For the same 300 mcg dose:
300 mcg ÷ 3,000 mcg/mL = 0.10 mL = 10 units
This is why two patients on identical 300 mcg doses may be injecting different volumes. The dose in mcg is the same; the volume in mL differs because their vials were reconstituted at different concentrations.
| Vial (9 mg) + water added | Concentration | 300 mcg dose in mL | Units on U-100 syringe |
|---|---|---|---|
| 2 mL | 4,500 mcg/mL | 0.067 mL | ~7 units |
| 3 mL | 3,000 mcg/mL | 0.10 mL | 10 units |
| 1.5 mL | 6,000 mcg/mL | 0.05 mL | 5 units |
Example calculations using a 9,000 mcg (9 mg) vial. Your vial size and reconstitution instructions may differ—always use your pharmacy label.
Two patients on the same 300 mcg dose can inject different volumes — the milligrams are fixed, but the milliliters follow your vial’s concentration.
How do you read your sermorelin pharmacy label?
Your prescription label should state the concentration explicitly — for example, “Sermorelin 4500 mcg/mL” or “Sermorelin 3 mg/mL.” Some labels will also specify the exact volume to inject for your prescribed dose. If your label shows a concentration but not the volume, use the formula above. If the label is unclear, call your pharmacy — this is exactly the kind of question they expect.
Do not use online calculators or forum tables as a substitute for your specific label. Compounded sermorelin vials are not standardized across pharmacies; concentrations vary based on the compound ordered by your clinician.
How do you read an insulin syringe in units versus mL?
Sermorelin is typically injected using an insulin syringe, which is marked in units for a 1 mL volume. On a U-100 insulin syringe:
- 100 units = 1 mL
- 10 units = 0.1 mL
- 5 units = 0.05 mL
- 1 unit = 0.01 mL
To convert your mL volume to syringe units, multiply by 100. For 0.067 mL: 0.067 × 100 = 6.7 units. For 0.10 mL: 0.10 × 100 = 10 units.
Most 1 mL insulin syringes have graduations at every 2 units. Measuring to the exact unit may require slight estimation on the syringe — this minor variation at small doses is generally clinically insignificant, but confirm with your pharmacy whether rounding up or down is appropriate for your specific dosing.
What your clinician is actually deciding when they set your sermorelin dose
The mcg number in your prescription is not arbitrary. Sermorelin protocols are individualized based on your IGF-1 baseline, age, weight, and goals. Starting doses are typically conservative — 100–300 mcg at bedtime is common — with titration based on clinical response and follow-up IGF-1 testing at 6–12 weeks. The goal is to stimulate a pulsatile growth hormone release that approximates the physiological pattern the body uses naturally, not to flood the system with GH.
Because sermorelin works by stimulating your own pituitary to produce GH (rather than administering exogenous GH directly), there is a natural ceiling on the hormonal response. This is part of why clinicians generally view sermorelin as a more physiological approach than exogenous growth hormone therapy.
Compounded sermorelin is not an FDA-approved drug. PepScribe connects patients with licensed clinicians who prescribe sermorelin compounded by licensed 503A pharmacies in the USA — no hidden overseas supply chain.
Frequently asked questions
How do I calculate my sermorelin dosage in mL?
The calculation depends on the concentration of your reconstituted vial. For example: if you add 2 mL of bacteriostatic water to a 9 mg (9000 mcg) vial, you get a concentration of 4500 mcg per mL. A 300 mcg dose would then be 0.067 mL (about 6.7 units on a 100-unit insulin syringe). Your pharmacy label or clinician instructions should provide the exact calculation for your specific vial — do not use generic online tables.
Why does my sermorelin dosage look different from what I read online?
Compounded sermorelin vials come in different concentrations depending on how much active peptide is in the vial and how it was reconstituted. A 9 mg vial reconstituted with 2 mL has a different concentration than a 6 mg vial with 3 mL. Always base your dose calculation on YOUR specific vial label, not general online references.
What does 300 mcg of sermorelin look like in mL?
It depends entirely on your vial concentration. At 3000 mcg/mL, 300 mcg is 0.1 mL (10 units on an insulin syringe). At 4500 mcg/mL, 300 mcg is 0.067 mL (~6.7 units). At 6000 mcg/mL, 300 mcg is 0.05 mL (5 units). Your prescription label specifies your concentration — use that number, not a general reference.
Can I adjust my sermorelin dose on my own?
No. Sermorelin is a prescription medication; dose adjustments are a clinical decision. Your clinician bases your starting dose on your weight, IGF-1 levels, and individual response. If you feel the dose is not working or is causing unwanted effects, contact your prescribing clinician before making any changes.
Does the amount of bacteriostatic water I add to sermorelin matter?
Yes. The volume of bacteriostatic water you add determines the concentration of your vial. Adding more water creates a lower concentration — the same dose in mcg occupies a larger volume in mL. Your pharmacy instructions specify how much water to add; follow those instructions precisely.