One scoop has about the same caffeine (175 mg) as a mug of coffee (2 cups). A measuring cup of coffee has typically 95 mg of coffee. A mug of coffee is my self-imposed limit because I have brief encounters with atrial fibrillation sometimes - varies from once a week to once every three or four months, basically unpredictable. Actually, I've never correlated caffeine with atrial fibrillation myself. Aside from needing some more energy, I was interested in pain relief. The first ingredient is malic acid which if consumed on a regular basis can reduce pain starting after a couple of days. I haven't personally noticed any pain relief because I have reservations about consuming too much caffeine and potential atrial fibrillation. I have severe neck pain that basically never stops. I get very little sleep and this is what appealed to me to try Juggernaut to have enough energy to make it through the day. I'm still doing it, but cautiously until I'm sure it won't trigger atrial fibrillation.The taste is okay. The second ingredient is maltodextrin and is made from corn, potatoes or rice and is highly refined. It has a high glycemic index, so it can cause spikes in blood sugar. The label doesn't indicate the percentage or how much is included except it is the second ingredient. This could possibly be the source of quick energy. I'm not young anymore, and I'm certainly not an athlete. This is probably more suited for the younger generation who can more likely handle this better than I can. My wife is less than half my age, so she is trying it before her workouts. Even though she is still in her twenties, she has infrequent rapid heartbeat every couple of years. She drinks coffee, but only one mug a day like me, except stronger. She does aerobic exercises quite regularly to maintain her lean body mass, so she is more capable to use this.I'm still using this periodically, but as I said earlier, I am being cautious. So far I've not had any side effects. I'm not diabetic, so the blood sugar spikes don't concern me. I just need some extra energy and pain reduction.