Though we strive for a perfect day of eating, sometimes getting all of the vitamins and nutrients we need from food alone just doesn’t work out (like if you’re trying a plant-based diet for the first time). When our diets fall short, certain supplements may help provide vital missing nutrients. But when is the best time to take vitamins? With so many different kinds (and some requiring an empty stomach before taking), it can be tricky to figure out what to take and when.

“Vitamins can help to fill nutritional gaps in a person’s diet,” explains Keri Gans, R.D.N., author of The Small Change Diet and podcast host of The Keri Report. “If an individual is on a special diet that limits or restricts certain foods, vitamins may help prevent nutritional deficiencies.”

Whether you’re taking a multivitamin or vitamins for brain health, the timing can sometimes determine their efficacy. Below, experts advise when to take vitamins, including the best time to take vitamin D, vitamin C, multivitamins, and more.

Is it better to take vitamins in the morning or at night?

“The best time to take vitamins depends on the vitamin you are taking,” explains Jim White, R.D.N., A.C.S.M. Ex-P, owner of Jim White Fitness and Nutrition Studios. Whether or not a vitamin is water- or fat-soluble usually dictates when and how it should be taken, but some vitamins also have a certain effect on the body that helps determine when you should add it to your routine.

“For example, B vitamins may help with energy production so it may make more sense to take it in the morning,” White says. The opposite is often true when taking magnesium for sleep.

But, as a general rule of thumb, the best time to take vitamins is whatever time you will remember to take them, Gans explains. “For some people that is in the morning with breakfast, and for others it’s in the evening when they get ready for bed.”

Ahead, find the best time to take a variety of vitamins based on each’s composition.

Vitamins B, C, and biotin (water-soluble vitamins)

Water-soluble vitamins can be taken any time of day, with or without food, White says. The best time to take water-soluble vitamins would be whenever you’re most likely to remember to take them. Additionally, “Water-soluble vitamins are not stored in your body tissue so they need to be regularly consumed,” White adds.

Common water-soluble vitamins include:

  • vitamin C
  • B vitamins
  • biotin

Vitamins A, D, E, and K (fat-soluble vitamins)

“Fat-soluble vitamins are different from water-soluble vitamins because they need to be consumed with a meal containing fat to help break it down,” White explains. “However, they can also be taken at any time throughout the day,” as long as they are consumed alongside a meal containing fat.

Common fat-soluble vitamins include:

  • vitamin A
  • vitamin D
  • vitamin E
  • vitamin K

When is the best time to take multivitamins?

Multivitamins generally contain both fat-soluble and water-soluble vitamins, Gans and White explain. It’s best to follow the rules for fat-soluble vitamins and take them any time of day you’ll be able to consume a meal containing fat.

Can I take vitamins on an empty stomach?

There is no specific rule against this, our experts explain. “Taking vitamins on an empty stomach is an individual thing—some people have zero side effects, while others do,” Gans notes.

However, White notes that water-soluble vitamins tend to be better tolerated on an empty stomach, but recommends that fat-soluble vitamins and multivitamins be taken with food “to prevent an upset stomach and help increase vitamin absorption.”

For those who take an iron supplement, taking it on an empty stomach for optimal absorption is recommended, per the Mayo Clinic. If you also take calcium, be sure to take it at a separate time from your iron supplement to make sure your body fully absorbs both.

Disclaimer: Dietary supplements are products intended to supplement the diet. They are not medicines and are not intended to treat, diagnose, mitigate, prevent, or cure diseases. Be cautious about taking dietary supplements if you are pregnant or nursing and be sure to consult your doctor before taking new supplements (or providing them to a family member) in any situation, as they can interfere with medication.