How much vitamin D should I take?
Official UK advice is to consider 10 micrograms daily through autumn and winter. Higher doses are available and are best taken on advice rather than by guessing.
Is buffered vitamin C easier on the stomach?
Many people find it is. Buffered forms pair the vitamin with a mineral to reduce acidity, which suits anyone who finds plain ascorbic acid uncomfortable.
Can I take vitamin C and zinc together?
Yes, and plenty of formulas combine them. Just add up the totals if you are also taking a multivitamin, since zinc in particular has an upper limit.
When should I start taking these?
Most people begin as the clocks change and the days shorten. Vitamin D in particular is taken through the whole of autumn and winter rather than started once you feel you need it.