Hi . That's really hard to say. Some people can drinking coffee all day and it doesn't affect them. Others are wired after only one cup. We're not medical experts, so it's best to check with your doctor, especially if you have a cardiac condition. I would guess though that it's best to listen to your body. Many people stop drinking coffee after 2 p.m. so they can sleep better at night. Hopefully, others will share their own experience here. Wishing you the best. - Lori (Team Member)