How many insulin‑type units on a 100‑unit/mL syringe correspond to one international unit (IU) of human growth hormone when the solution concentration is 10 IU per milliliter?

Insulin Units and IU Conversion for Growth Hormone

When human growth hormone (hGH) is prepared at a concentration of 10 IU per milliliter, drawing 0.1 mL on a standard 100-unit/mL insulin syringe (which equals 10 insulin-type units on the syringe) will deliver exactly 1 IU of growth hormone.

Understanding the Conversion

The conversion is straightforward because it's based on volume, not unit equivalence:

• Standard insulin syringes are calibrated for U-100 insulin (100 units of insulin per mL), where each marking represents a specific volume 1
• The 1 mL insulin syringe holds up to 100 units of U-100 insulin, which equals 1.0 mL of volume 1
• Each "unit" marking on a U-100 insulin syringe represents 0.01 mL of volume 1

The Mathematical Relationship

For hGH at 10 IU/mL concentration:

• 1 IU of hGH = 0.1 mL of solution 2, 3
• 0.1 mL = 10 "units" on a standard U-100 insulin syringe 1
• Therefore: 1 IU of hGH = 10 insulin-type units on the syringe scale

This means the ratio is 10:1 (10 syringe units per 1 IU of hGH at this concentration).

Critical Safety Considerations

You must use the correct syringe matched to your solution concentration to avoid dangerous dosing errors 1:

• U-100 syringes are standard in the United States and have scale markings appropriate only for U-100 concentration 1
• Mismatches between syringes and solution concentration can lead to serious underdosing or overdosing 1
• Each syringe has scale markings appropriate for only one concentration, and using the wrong syringe type is a common source of medication errors 1

Practical Application Example

If prescribing 4 IU of hGH from a 10 IU/mL solution 2:

• Calculate volume needed: 4 IU ÷ 10 IU/mL = 0.4 mL 2
• On a U-100 insulin syringe, draw to the 40-unit marking (since 0.4 mL = 40 units on the syringe scale) 1
• This delivers exactly 4 IU of growth hormone 2

Common Pitfalls to Avoid

Never confuse insulin units with IU of growth hormone - they measure completely different substances and are not interchangeable 1:

• The syringe markings represent volume, not biological activity of the medication 1
• Always calculate the volume needed first based on your solution concentration, then draw that volume using the syringe markings 1
• Avoid syringes with detachable needles as permanently attached needle syringes deliver better dose accuracy with less dead space 1