Maximum Dose for Humulin R U-500 Pen
The Humulin R U-500 pen delivers insulin in 5-unit increments with a maximum single injection dose of 300 units per injection. 1
Device Specifications
- U-500 pens dispense in 5-unit dose increments, which is different from standard U-100 pens that typically use 1-unit or 0.5-unit increments 1
- The maximum dose that can be dialed and injected in a single administration from the U-500 pen is 300 units 2
- Each U-500 pen cartridge contains 1,500 units total (3 mL at 500 units/mL concentration), allowing for multiple injections before the pen is depleted 3
Clinical Context for U-500 Use
U-500 insulin is specifically indicated for patients requiring more than 200 units of insulin per day, typically those with severe insulin resistance 4, 5
Key advantages of U-500:
- Reduces injection volume by 80% compared to U-100 insulin (same dose in one-fifth the volume) 3, 6
- Functions as both basal and prandial insulin due to its prolonged pharmacodynamic profile 3, 7
- Can be administered as a convenient twice-daily regimen as monotherapy 4
- Improves patient compliance by reducing the number of injections needed 4, 6
Critical Safety Considerations
Dosing Errors - Major Pitfall
- The 5-unit increment means each click delivers 5 units, not 1 unit - this is the most common source of dangerous dosing errors 1
- Patients and providers must understand that dialing "10" on a U-500 pen delivers 50 units, not 10 units 2
- Never use U-100 syringes to draw up U-500 insulin from vials, as this leads to five-fold overdosing 3
Pharmacodynamic Properties
- Onset of action is delayed 2.5+ hours after injection, making U-500 unsuitable as a premeal bolus for immediate postprandial glucose control 7
- Duration of action extends with higher doses - 200-unit doses last significantly longer than 100-unit doses 7
- This prolonged action necessitates extended dosing intervals to avoid stacking doses and causing hypoglycemia 7
Common Adverse Effects
- Hypoglycemia risk increases with U-500 use, particularly when transitioning from U-100 insulins 4, 5
- Weight gain is a consistent side effect 4
- Symptomatic hypoglycemia events increase modestly (from 2.0 to 3.3 events per patient per year) after U-500 initiation 5
Proper Injection Technique
When administering any dose from the U-500 pen:
- Prime the pen before each injection to ensure unobstructed flow 2
- Insert needle fully into subcutaneous tissue before pressing the dose button 2
- Keep pressure on the button until the needle is completely withdrawn to prevent incomplete dosing 2
- Dispose of needles immediately after use; never leave attached to the pen 2
- Never share pens between patients due to contamination risk 2