greg_boulder said:Concentration choice is a precision decision, not a preference.
Quick syringe math for dosing arithmetic dosing: if your vial is reconstituted at 5mg/2mL, that's 2.5mg/mL. For a 0.25mg dose you need 0.1mL = 10 units on an insulin syringe.
I keep a chart on my fridge:
- 0.25mg = 10 units
- 0.5mg = 20 units
- 1.0mg = 40 units
- 1.25mg = 50 units
Always double-check your concentration before drawing up!
One thing that is still open after MASHdoc_SA’s answer:
How to check the arithmetic without trusting a website calculator, since three calculators gave me three answers?
DanielChem_CHI said:Quick syringe math for dosing arithmetic dosing: if your vial is reconstituted at 5mg/2mL, that's 2.5mg/mL.
Compounding pharmacy dose accuracy check for dosing arithmetic: I always verify my first dose from a new vial by weighing it on a milligram scale. Draw up your dose, weigh the syringe, subtract empty syringe weight, compare to expected water weight at that volume.
For a 10-unit dose (0.1mL): expected weight ~100mg of water. If it's significantly off, your syringe may be inaccurate. Cheap insulin syringes can have ±5% volume accuracy. Spring for quality brands like BD or Terumo.
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Resolved. I wrote mg, ml and mg/ml on the vial in marker and did the division in that order, and the two of us now get the same number every time.
VanRx_Mike said:Compounding pharmacy dose accuracy check for dosing arithmetic: I always verify my first dose from a new vial by weighing it on a milligram scale.
Agreed, and it is worth saying that rounding to the nearest whole unit is usually acceptable at maintenance doses and is not acceptable at the bottom of a ladder, where one unit can be a fifth of the intended dose.