When we don't get enough sleep, many of us reach for a cup of coffee to give us an extra boost. The National Coffee Association says more than 60 percent of Americans drink at least one cup each day.

The National Sleep Foundation says it is best to drink your last cup of coffee at least six hours before bed to avoid the caffeine affecting your sleep. Their research also shows drinking too much coffee or any caffeine, especially late in the day, can interfere with your regular sleep cycle and cause symptoms like insomnia, restlessness, fast heartbeat, or even muscle tremors.

How much caffeine is too much? The National Sleep Foundation says adults shouldn't consume more than 500 milligrams of caffeine in a day. That equals roughly four cups of home-brewed coffee.

According to Harvard School of Public Health, a large regular brew coffee from a coffee shop contains 300 to 400 milligrams of caffeine. That is the same as three cups brewed at home, four Red Bull energy drinks, seven cans of Diet Coke, or almost 12 cups of green tea.