Insulin days supply (pens and vials)
Days supply including priming units and the opened-product discard date.
Inputs
5 of 6Pens or vials.
pens or vials
A 3 mL U-100 pen holds 300 units; a 10 mL U-100 vial holds 1000.
units
units/day
per day
Priming per injection
days
When to use
- Billing insulin or answering a refill-too-soon reject.
Pearls and pitfalls
- Most pens and vials are discarded 28 days after opening; some last 42 or 56 days (check the product).
- Pens are usually primed with 2 units before each injection.
- Payers may require days supply to reflect the discard date when it is shorter.
Why use
Both the units math and the discard limit, which is where most billing errors happen.
Days = total units ÷ (daily dose + priming units × injections per day); limited by discard days after opening × packages