DayQuil, a popular over-the-counter medication for cold and flu symptoms, typically contains ingredients like pseudoephedrine or phenylephrine, which can cause sleep disturbances in some individuals. Does DayQuil keep you awake, the primary purpose is to alleviate symptoms during the day without causing drowsiness, sensitive individuals may experience insomnia or restlessness after taking it. It's advisable to avoid taking DayQuil close to bedtime if you're prone to sleep disruptions or consult a healthcare professional for alternative remedies.