i have a great dane puppy of 6 months old who over the past 2 weeks his joints keep clicking every time he moves. i have asked the vet for some vitamin c tablets but he said there is no vitamin c tablets just a injection. could any one help as i cant get any should i get him normal vitamin tablets that we would take

Why not? Vitamin C is Vitamin C is Vitamin C. My guinea-pig has a quarter of a soluble Vitamin C tablet in her water bottle, because they don't synthesize it themselves.
:)

Yes, get him some normal ones...500mg ones I believe once a day.

Also give him some cod liver oil in one of his feeds, or glucosamine.

I give my fast growing pups ascorbic acid which is another form of vit C.  I get it sent to me by mail order from a herbal company.

my greatdane gets, my multibionta advanced formula from seven seas 1 aday plus tuna and the oil in food you can get poweder (shark?) ask at pet shop