Your blood pressure may get used to daily caffeine within three weeks
In one trial of 11 adults taking caffeine daily, its blood-pressure rise had faded to near zero by day 20. The nervousness and poor sleep had not.
What the study found
In 11 adults, daily caffeine's blood-pressure rise had faded by day 20
Eleven healthy adults took 3 mg of caffeine per kg of body weight daily for 20 days, and a placebo for 20. Over the first eight days systolic pressure ran 7.8% higher; by day 20 the gap was near zero, while nervousness, poor sleep and extra urination carried on.
The caveat · Too few to say how fully it fades
Eleven people give only a rough picture of when the rise fades and how completely. One moderate dose was tested, about 210 mg for a 70 kg adult, not the range people drink.
What we don't know
In one small trial, daily caffeine's blood-pressure rise faded to near zero within three weeks; pooled trials found about 2 mmHg that was larger in longer trials. Whether the body adapts fully or only partly is unsettled.