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If you use Vitamin C, use acid neutral vitamin C or else you'll encounter problems from the acidity of the vitamin C. Sugar in your blood or intestine slows absorption, so take on an empty stomach or before exercising. Dosage is variable. Some people need 10 grams a day. Some people only need 500mg a day. Larger doses (above a gram or so) need to be divided into several smaller doses and taken with large amounts of water throughout the day.
Drinking alcohol depletes glutathione in the liver and increases the need for vitamin C.