I buy all my supplements from Amazon. And I make sure they are a reputable brand, and in the doses that I require. If possible (such as Vit K and Vit C) I go for ‘natural source’.
Of course the trick is to work out which brands are actually ‘reputable’ and not scam merchants. So many are. My basic criteria involve glass packaging, preferably brown glass, and a brand that offers a good range of products, not just one trendy ‘money earner’.
Can’t see the point of cheap multi vits and mins. They are usually synthetic vits with much less bioavailability, so you either don’t absorb them properly, or you need bigger doses to get the same benefit. Also watch out for the type of the vitamin. MAny, like Magnesium, C, E and K come in all sorts of different varieties. No point in spending good money on something that won’t be absorbed, and won’t do what you think you are paying for. Or - worse - causes stomach upset and diarrhoea, as some of the Magnesiums may do.
Yes! It IS a minefield! 