How many hours/days does ascorbic acid stay in the body through an intramuscular injection?

Unknown. Ascorbic acid is generally given by mouth and there is much debate on how long it lasts in the human body. The half life is described in the medical literature as being anywhere between 30 min and 17 days. In general we think of vitamin c levels easily reaching capacity and having a relatively short half life which is why we advise for daily oral supplementation.