The number one thing that confuses people new to peptides is the difference between the dose and the syringe markings. A “10 unit” draw is not a “10 mcg” dose. Getting this straight is the difference between an accurate dose and a tenfold error, so it is worth five minutes.
The key idea: Two completely different things are being measured. mcg and mg measure the amount of peptide. Units measure liquid volume on the syringe. How they line up depends entirely on how you mixed the vial.
mcg and mg: the amount of drug
Micrograms (mcg) and milligrams (mg) measure how much actual peptide you are taking. The only conversion to remember:
1 mg = 1,000 mcg. So a “0.5 mg” dose and a “500 mcg” dose are identical. This is the number your protocol specifies, and it does not change no matter how you reconstitute the vial.
Units: a mark on the syringe
The numbers printed on an insulin syringe measure volume, not peptide. On a U-100 syringe, the whole barrel is 1 mL and it is divided into 100 units, so:
- 100 units = 1 mL
- 50 units = 0.5 mL
- 10 units = 0.1 mL
“Units” say nothing about how much peptide is in that volume. That depends on the concentration of your solution.
How they connect
The bridge between the two is concentration, set when you reconstitute (peptide amount divided by water added). Work through an example:
A 10 mg vial mixed with 2 mL of BAC water = 5 mg/mL. To take a 0.5 mg dose: 0.5 ÷ 5 = 0.1 mL = 10 units. Now mix that same 10 mg vial with 4 mL of water (2.5 mg/mL) and the same 0.5 mg dose becomes 20 units. Same dose, different mark, because the concentration changed.
That is the whole trap: units are meaningless until you know your concentration. Never copy someone else’s “unit” number unless you reconstituted your vial exactly the same way.
Quick reference
| Term | Measures | Fixed by |
|---|---|---|
| mcg / mg | Amount of peptide | Your protocol |
| mL | Liquid volume | Dose ÷ concentration |
| Units | Volume on the syringe (mL × 100) | Your concentration |
Let the calculator do it
You never have to run this by hand. Enter your vial size, water volume, and intended dose into the reconstitution calculator and it returns the exact volume and unit mark, drawn on a syringe. For the wider fundamentals, see Peptides 101: reading your dose.
This article is educational and reference-only. It is not medical advice. Always verify any dose independently and consult a qualified professional before making health decisions.
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