Vitamin C and Sleep: Can Supplements Cause Insomnia?

While taking vitamin C in high doses (i.e. more than 2000 mg/day) has not been scientifically proven to cause insomnia, some people do report sleep issues when taking high doses of vitamin C, especially if taken close to bedtime. High doses of vitamin C can stimulate the body and make it harder to fall asleep.

For most people, taking a normal dose of vitamin C (usually around 1000 mg/day) is unlikely to cause insomnia. However, if you are sensitive to caffeine or other stimulants, you may want to avoid taking vitamin C supplements in the evening to reduce the risk of sleep problems. If you are concerned about insomnia from vitamin C, talk to your doctor.