Answer
Humulin S is a clear soluble preparation with a shorter action profile. Insulatard is a cloudy isophane suspension with more gradual, prolonged absorption.
Sources for this answer
- Insulatard Penfill 100 international units/ml suspension for injection in cartridge. — Current selected SmPCemc · Summary of Product Characteristics
- HUMULIN S (Soluble) 100IU/ml solution for injection in cartridge — Current selected SmPCemc · Summary of Product Characteristics