How long can Humulin R stay out of the fridge?
Humulin R (regular human insulin)
31 days at room temperature, opened or not. After that, throw it out even if insulin is left.
- U-100 vial
- 31 days
Good to know
- Before opening, keep it in the fridge (36°F to 46°F) until the expiration date on the box.
- Keep below 86°F (30°C), away from heat and direct light. Never freeze; throw out insulin that froze.
- Humulin R U-500 has its own limits: 40 days for the vial and 28 days for the KwikPen.
- Whether an opened pen can go back in the fridge depends on the product. Check the label.
Source: the FDA label on DailyMed, last checked October 14, 2026. Labels change, so check the product in hand. Questions about a patient's medicine go to the pharmacist.
Working out the days supply?
The insulin & GLP-1 days supply calculator counts the in-use limit for you, and tells you how many boxes and pens to give.
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