Emergen-C is a powdered vitamin C supplement that is designed to boost your immune system and counteract vitamin deficiencies caused by poor diet, illness, and pregnancy. Learn about Emergen-C, whether it really works to prevent colds and the side effects of taking it in large doses.

If you still decide to take Emergen-C, keep it to one serving daily. If you're taking statins or chemotherapy medications, talk with your healthcare provider before using the supplement. Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles.

Directions: Ages 14 and up, one (1) packet daily. Empty contents into a glass, add 4-6 oz of water, stir. For lighter flavor, mix with more water. Do not exceed suggested use.

“Emergen-C is a vitamin C supplement, and there's no evidence that it benefits people with the cold or influenza or [that it] affects your propensity to get the cold or the flu,” says Amesh Adalja, MD, an infectious disease physician and a senior scholar at the Johns Hopkins Center for Health Security.

Overall, vitamin C is a water soluble vitamin that does not have sedating or stimulating effects on energy levels in the body. So that means you can truly take vitamin C any time of day without worrying about disrupting your sleep.

The volume of dye necessary to facilitate this change is directly related to vitamin C content, and so this factor was of primary concern. Results indicate that there is likely no difference between hot and room-temperature preparations.

It is much easier to see just how big of a dose these supplements provide. Airborne recommends taking no more than three tablets per day, but this is still over 3000% more vitamin C than you actually need. Emergen-C also cautions against using more than two packets.

Ages 14 and up, one (1) packet daily. Empty contents into a glass, add 4-6 oz of water, stir. For lighter flavor, mix with more water.

Overall, vitamin C is a water soluble vitamin that does not have sedating or stimulating effects on energy levels in the body. So that means you can truly take vitamin C any time of day without worrying about disrupting your sleep.

The evening is not the best time because vitamin C is acidic and can cause problems when consumed on an empty stomach, especially in people with gastroesophageal reflux disease – of course the dosage matters.

The best time to take vitamin C is on an empty stomach. Because it's a water-soluble vitamin, it doesn't require fat for absorption, which means maximum absorption happens when there's no competition.

Because it's a water-soluble vitamin, Dr. Qamar recommends taking it on an empty stomach either first thing in the morning or between meals. However, if you have acid reflux or indigestion, she said it's easier on your stomach to take the supplement with a meal.