Question 1

What is the half-life of caffeine?

Accepted Answer

The half-life of caffeine averages about 5 hours for most adults, with a typical range of 2 to 8 hours (EFSA, 2015). This means if you consume 200mg of caffeine, approximately 100mg will remain after 5 hours. Individual factors like genetics, lifestyle, and age can influence this range.

Question 2

How long does caffeine stay in your system?

Accepted Answer

Caffeine typically takes 5 to 6 half-lives to be effectively cleared, which means roughly 25 to 30 hours for a typical adult. Noticeable effects usually subside within 6 to 10 hours. Many people find it helpful to stop caffeine at least 6 to 8 hours before bedtime.

Question 3

What are common caffeine intake guidelines?

Accepted Answer

According to the FDA and EFSA, a commonly referenced guideline for adults is up to 400mg of caffeine per day (about 4 cups of brewed coffee). Some populations, such as those who are pregnant, may choose a lower limit around 200mg/day. For children, EFSA references 3mg per kg of body weight per day. Individual tolerance varies.

Question 4

Does smoking affect how long caffeine lasts?

Accepted Answer

Research suggests that smoking can speed up caffeine clearance. Smokers tend to process caffeine faster, with an estimated half-life of about 3 hours compared to 5 hours for non-smokers.

Question 5

Does caffeine last longer during pregnancy?

Accepted Answer

Published research indicates that caffeine clearance slows during pregnancy. The estimated half-life may extend to around 10 hours in early pregnancy and up to 15-18 hours later on (Knutti et al., 1981; EFSA, 2015). This is one reason many guidelines suggest a lower daily caffeine limit during pregnancy.