Question: how long does it take for insulin to bring down blood sugar?
Answer: Types of Insulin Rapid-acting insulin starts to lower blood sugar within 15 minutes and its effects last for 2 to 4 hours. Short-acting insulin starts to work within 30 minutes and its effects last for 3 to 6 hours. Intermediate-acting insulin starts to work within 2 to 4 hours and lasts for 12 to 18 hours.