Caffeine is a familiar drug that stimulates the nervous system. When it enters the body, caffeine raises the heart rate and blood pressure, increasing energy levels and improving the mood.
Caffeine acts quickly, and many people notice the effects within minutes. They last until the body fully metabolizes the drug. This duration depends on several factors.
Each person will feel the effects differently, and some may last longer than others. People who are pregnant or have difficulty sleeping should be careful about timing their caffeine intake and may want to avoid it altogether.
How long does it take to metabolize caffeine?
Caffeine has a half-life of about 5 hours.
Someone who consumes 40 milligrams (mg) of caffeine will have 20 mg remaining in their system after 5 hours.
When do effects peak?
Levels of caffeine peak in the blood within about 15–45 minutes of consumption.
They are then quickly metabolized by the liver.
Most people notice the strongest effects during this time, and many report feeling jittery, needing to urinate, and having sudden bursts of energy. These symptoms tend to go away as the caffeine starts to break down.