Caffeine blocks the feeling of tiredness for several hours. Moderate intake is linked to alertness and is safe for most adults.
Too much can cause jitters, poor sleep and a fast heartbeat. Tea and coffee with meals can reduce iron absorption.
If you stop suddenly, expect a headache and tiredness for a few days. Cut down gradually.
This is general information, not a substitute for medical advice. If you have a medical condition, are pregnant, or take regular medication, talk to your doctor first.