Does vitamin d break a fast?

Vitamin D supplements come as tablets, drops and softgels (a little oil inside a gel capsule). A daily dose is measured in micrograms. In the US, a supplement label only has to show calories once a serving reaches 5. So a label with no calorie line means under 5.

Across this site's four goals, vitamin D is safe for weight loss, autophagy, gut rest and blood sugar. It has no sugar or protein, and a small capsule gives the gut almost nothing to digest.

When to take it matters more. Vitamin D dissolves in fat. A study gave 50 healthy older adults one large dose of vitamin D3 each. Blood levels were 32% higher when the dose came with a meal containing fat than with a fat-free meal. That is early evidence from one short study, and it points to taking vitamin D with a meal in your eating window.

More is not better. For most people who choose to take vitamin D, 10 micrograms a day is enough. Adults should not take more than 100 micrograms (4,000 IU) a day unless a doctor advises it. Too much over a long time can build up calcium in the blood, which can weaken the bones and damage the kidneys and heart. Some medical conditions lower the safe amount, so ask your doctor if you have one. Sunlight on your skin cannot cause a vitamin D overdose.

If your doctor has prescribed a specific vitamin D dose, follow it exactly. Fasting is never a reason to change it.