caffeine takes how long effect
How long does it take caffeine to take effect on the body? how long do the effects last? Report Abuse. 1  It depends; those who drink lots of coffee become 'caffeine-tolerant'. If they were to have a coffee late in the evening it wouldn't make much difference. 2  it can take 15-20 minutes.. the effects can last a few hours.. 3  is a stimulant and it will elevate heart rate, increase blood flow, and raise body temperature.