Where's the best place to buy vitamins?

[onitlikeacarbonnet]

I'm hypothyroid and have had a few blood tests which show I could benefit from supplementing a few vitamins.
My b12, vit d and ferritin are all low in range and I'd like to add a vit c and b complex for good measure.
I've bought some in the supermarket but figure there must be a better quality product out there. The dosages vary so much from one to the next.
Any recommendations or suggestions would be greatly appreciated.

I use Nature's Best online. Seem to be good quality, high strength and fair price.

I've bought from health span before and Amazon - jarrow and solgar brands.

Re:b12 make sure you get a sublingual tablet as sometimes it can't be absorbed very well through the gut.