mcg vs mg: Peptide Dosing Units Explained
Understand the difference between mcg and mg, how to convert between them, and why unit mismatches are the most common peptide calculation error.
The Core Difference
mg (milligram) and mcg (microgram) are both units of mass. The relationship is simple:
- 1 mg = 1,000 mcg
- 1 mcg = 0.001 mg
Peptide vials are commonly sold in mg (e.g. 5 mg, 10 mg). Dosing targets are often expressed in mcg (e.g. 250 mcg, 500 mcg). This constant switching between the two is the most common source of calculation errors.
Quick Conversion Reference
| mg | mcg |
|---|---|
| 0.1 mg | 100 mcg |
| 0.25 mg | 250 mcg |
| 0.5 mg | 500 mcg |
| 1 mg | 1,000 mcg |
| 2 mg | 2,000 mcg |
| 5 mg | 5,000 mcg |
| 10 mg | 10,000 mcg |
Where the Confusion Happens
Vial label vs dose target
A vial labeled "5 mg" contains 5,000 mcg. If your dose target is 500 mcg, that vial contains exactly 10 doses — but only if you do the conversion correctly. Treating the vial as "5" and the dose as "500" without converting first leads to a 1000× error.
Calculator inputs
ClearDosage accepts both mg and mcg as inputs for peptide amount and desired dose. The unit toggle is visible next to each field. Always confirm the unit displayed matches what you're entering.
Protocol documents
Written protocols often switch units mid-document. A guide might list vial size in mg and daily dose in mcg. Always normalize to one unit before doing math.
The Unit Converter Tool
ClearDosage's Unit Converter handles mcg ↔ mg conversions instantly:
- Enter your value in either field
- Select the source unit
- The converted value appears in real time
The converter also handles mL ↔ units conversions for U-100 and U-40 syringes, and IU conversions for peptides that use international units.
How ClearDosage Handles Units
In the main calculator:
- Peptide Amount — Enter the vial amount in either mg or mcg using the unit selector
- Desired Dose — Enter your target dose with the inline unit toggle (tap mg ⇄ to switch between mcg and mg)
- Results — Displayed in both mL and syringe units for your selected syringe type
The calculator always shows the unit label next to each value. If a result looks unexpectedly large or small, the first thing to check is whether the units match your intent.
Practical Checklist
Before entering values into any calculator:
- [ ] Confirm vial label unit (mg or mcg)
- [ ] Confirm dose target unit (mg or mcg)
- [ ] Convert both to the same unit before entry, or use the unit selector in the calculator
- [ ] Double-check: does the result (in mL or syringe units) look reasonable for a single injection?
A single subcutaneous injection is typically 0.1–1.0 mL. If your result falls far outside this range, a unit mismatch is the most likely cause.
Example: Converting a Typical Protocol
Protocol: 10 mg vial, 2 mL bacteriostatic water, 500 mcg dose
Step 1: Convert vial to mcg → 10 mg = 10,000 mcg Step 2: Concentration = 10,000 mcg ÷ 2 mL = 5,000 mcg/mL Step 3: Draw = 500 mcg ÷ 5,000 mcg/mL = 0.10 mL Step 4: On a U-100 syringe → 10 units
Enter these values directly into the ClearDosage calculator and it performs all four steps automatically.
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