Is it OK to drink an energy drink before a workout?

Short answer

Performance does go up: across 34 studies, muscular endurance, endurance and jumping improved. But top blood pressure rose by about 5, drinking close to 1 L at once also changed the ECG, and 1 in 3 people slept badly.

Is it OK to drink an energy drink before a workout?
'Energy drink → more power, but hard on the heart' — true?
Lots of people drink an energy drink before training. We checked whether workouts really go better, and what happens to the heart and to sleep.
Workouts really did go better
34 studies: muscular endurance, endurance and jumping improved
An analysis that pooled 34 studies of a single energy drink before exercise found improvements in strength and muscular endurance, endurance, jumping and sport-specific moves. Only short sprints showed no difference.
It wasn't just the caffeine
Adding taurine worked better
In the 34-study analysis, performance gains rose with the amount of taurine, not the amount of caffeine. A 2025 analysis of 12 studies also found that caffeine plus taurine beat either one alone for short, hard efforts and reaction time.
But blood pressure went up
Top number up 4.71, 1 hour after drinking
An analysis of 17 randomized trials found energy drinks raised top (systolic) blood pressure by 4.71 at 60-80 minutes and bottom (diastolic) blood pressure by 4.51 at 2 hours. Heart rate and the ECG showed no difference.
Close to 1 L at once was a different story
Even the ECG changed
When 34 people drank 946 mL within 1 hour, the time the heart takes to reset between beats (the QT interval on an ECG) grew by 17.9-19.6 ms, versus 11.9 ms for a fake drink. In an 18-person test with caffeine matched at 320 mg, top blood pressure at 6 hours was higher only after the energy drink: 4.72 vs 0.83.
Sleep and nerves paid a price too
1 in 3 slept badly
When 90 people drank an energy drink with 3 mg of caffeine per 1 kg of body weight (210 mg for a 70 kg (154 lb) person), 31.2% had insomnia, 3 times the 10.4% after the same drink without caffeine. Nervousness was 13.2% vs 0%. In a 38-person test with 750 mL-1 L, 11% had unpleasant symptoms.
Summary: performance goes up, the cost depends on the amount
The more at once, the bigger the strain on the heart
Energy drinks improved muscular endurance, endurance and jumping. The cost: top blood pressure rose by about 5, and in tests where people drank 946 mL within 1 hour, the ECG changed too. 1 in 3 slept badly. Weigh the workout boost together with how much you drink and your sleep.