Actually, it depends on the nutrient. Magnesium is a mineral by the way, not a vitamin. Are you taking a multi or separate nutrients? Some fat soluble nutrients and fats are best kept refrigerated if you're not going to take them right away to prevent oxidation, such as Vitamin E. If the bottles are clear, keep them away from light. Otherwise, if they're in your house and not sitting outside in the sun, just put them in a darker rather than well lit place, away from sunlight. If you take them regularly they shouldn't sit long enough to oxidize. Better quality supplements are never sold in clear bottles, but always in darkened ones.
Thanks Paxiled.
I'm taking a multi for men, Vitamin D, omega 3, and Magnesium gylcinate. None of the bottles are clear.
I did keep them in the fridge before but I was worried about humidity?