Vitamin C

Vitamin C intake can only be obtained from the diet or supplements, and is needed throughout the day, as the the vitamin is secreted in urine 2-3 hours after consumption.

For general immune system maintenance you may well need around 200mg per day (well above the typical RDA). Look to include plenty from the diet ideally. 

As a therapeutic dose, around 1,000mg per day is optimal – preferably in a slow release supplement formula. The upper limit for adults is generally thought to be around 2000mg per day.