Caffeine Half-Life in Adults
The half-life of caffeine in healthy adults ranges from 2.5 to 10 hours, with a mean of approximately 3-5 hours. 1, 2, 3
Standard Half-Life Parameters
- In healthy adult males and non-pregnant females, the mean caffeine half-life is 3.4 hours (range 2-5 hours) 4
- The FDA drug label for caffeine citrate reports that in adults, the half-life is approximately 5 hours 1
- Research literature consistently documents a range of 2.5-10 hours for caffeine elimination half-life in healthy adults 3
Factors That Significantly Alter Half-Life
Pregnancy
- Pregnant women have dramatically prolonged caffeine half-life of 8.3 hours (range 3-16 hours), more than double the non-pregnant state 4
- This prolonged half-life returns to normal within one month after delivery 4
- The slower metabolism during pregnancy is why pregnant women should limit caffeine to ≤200-300 mg/day 5
Hepatic Disease
- Patients with alcoholic hepatic disease show severely prolonged half-lives of 60-168 hours due to compromised liver function 6
- This represents a 10-30 fold increase compared to healthy adults 6
Smoking
- Smoking decreases the half-life of caffeine, accelerating its metabolism 2
Age-Related Variations
- Neonates have the longest half-life at approximately 3-4 days (72-96 hours) due to immature hepatic enzyme systems 1
- By 9 months of age, caffeine metabolism approximates adult values with a half-life of 5 hours 1
- Children and adolescents metabolize caffeine more rapidly than adults 7
Metabolism and Elimination
- Caffeine is extensively metabolized in the liver by cytochrome P450 1A2 (CYP1A2) to more than 25 metabolites 1, 3
- Less than 5% of ingested caffeine is excreted unchanged in urine in adults 1, 2, 3
- In neonates, approximately 86% is excreted unchanged due to immature metabolism 1
Clinical Implications
- The 2.5-10 hour half-life range explains why caffeine consumed in the afternoon or evening can interfere with sleep 7
- Peak plasma concentrations occur 30 minutes to 2 hours after oral administration 1
- There is considerable inter-individual variability in caffeine handling due to both environmental and genetic factors 3