For most supplements, the best time to take them is whenever you will actually remember to. Consistency beats clever timing. But a handful do work better at a particular time or with a particular meal, and a few are worth keeping apart from each other. Here is a simple daily pattern that covers the ones where timing genuinely matters.
Morning, with or without food
Iron is best taken earlier in the day, on a fairly empty stomach if your gut tolerates it, with a source of vitamin C to boost absorption, and away from coffee, tea and calcium. B vitamins can be mildly energising for some people, so morning suits them too.
With your main meal
The fat-soluble vitamins, vitamin D, E and K, plus omega-3, all absorb better with food that contains some fat. The largest meal of the day is the natural slot. Calcium, if you take a larger dose, absorbs better split across two smaller doses with meals than taken all at once.
Evening
Magnesium, particularly the gentler glycinate form, is mildly calming and suits the evening, which is why it features in most sleep stacks. Anything you take specifically for sleep belongs here too.
The separations that matter
Two things override the general pattern. If you take thyroid medication, take it alone first thing and keep minerals at least four hours away, covered in the levothyroxine guide. And keep iron and calcium in different parts of the day, since calcium blunts iron. Beyond those, the clashes are minor and covered in what not to take together.
To check the timing of any supplement against a medication you take, the free checker will show you the result and the reasoning.