When and how to take vitamin supplements to get the most out of them

You might take supplements because you’re eating less on a GLP-1 medication.

Or maybe you’re a vegetarian and low on vitamin B12, or you have a health condition that depletes your iron.

Supplements can cost a lot, and they can interact with certain medications. To benefit from them, it’s important to know when and how to take them, and whether they can affect medications you’re on.

When are dietary supplements helpful?

It’s always best to try to get most, if not all, of your nutrients from what you eat. But if that’s not possible, a multivitamin or certain vitamins and minerals might help make up for what you’re missing.

Who might benefit from taking a supplement?

• Adults taking GLP-1 medications who are eating significantly less
• Vegetarians and vegans low in vitamin B
• People deficient in iron
• Older adults with difficulty absorbing certain nutrients
• Anyone pregnant or breastfeeding
• Individuals with digestive disorders that affect how well their bodies absorb nutrients

Which supplements should not be taken together?

These supplements shouldn’t be taken together, because they block each other from the body absorbing it:

• Iron and calcium: Calcium can reduce the amount of iron the body absorbs.
• Vitamin C and vitamin B12: Over time, taking high doses of vitamin C and B12 at the same time may reduce how well the body absorbs vitamin B12.

With these supplements, it’s important to take them two to four hours apart. So, if you take an iron supplement in the morning, you can have a calcium supplement at lunch or dinner.

Which supplements are best taken together?

• Calcium and vitamin D: you need vitamin D to properly absorb calcium.
• Vitamin C and iron: Vitamin C helps absorb iron from plant-based sources, such as beans. It’s good to take an iron supplement with citrus fruit, such as oranges or orange juice, or citrus-rich vegetables such as tomatoes or bell peppers.
• Magnesium and vitamin D: Magnesium helps convert vitamin D into its active form.
• Vitamin D and vitamin K: Vitamin D helps the body absorb calcium, while vitamin K activates proteins that help calcium reach and incorporate into bone. Together, they help make bones healthy.

Are supplements best taken with food?

Fat-soluble vitamins, such as the below vitamins, dissolve in fat. Your body absorbs them best when you take them with food, ideally a healthy fat such as an avocado:

• Vitamin A
• Vitamin D
• Vitamin E
• Vitamin K

Water-soluble vitamins, such as these, dissolve in water and can be absorbed on an empty stomach:

• Vitamin C
• Vitamin B12 and all seven other B-complex vitamins.

You can take water-soluble vitamins on an empty stomach. If that makes you nauseated, you can have them with food.

Are there supplements you should not take with medications?

• Ginkgo biloba and blood thinners: Taking these together raises the risk of severe bleeding.

• Calcium or iron with levothyroxine: Calcium and iron block your body from absorbing levothyroxine, a thyroid medication. If you’ve taken a dose of levothyroxine, it’s best not to have calcium or iron for at least four hours.

• Vitamin K with warfarin: Vitamin K, which is often found in leafy greens, can weaken the effect of warfarin, a blood thinner.
• St. John’s wort with birth control pills, antidepressants and blood thinners: St. John’s wort can make these medications less effective.

When is the best time to take vitamins?

• Magnesium glycinate to calm you and potentially help you sleep should be taken in the evening. If you’re not taking it to help you sleep, it can be taken anytime.
• Magnesium citrate for constipation can be taken in the morning or evening.
• Vitamin B12, if it makes you feel alert after having it, should be taken in the morning or early in the day
• Multivitamins should be taken with a meal, ideally, and early in the day especially if they contain caffeine, or an energizing herb, such as ginseng.

It’s best to get as many nutrients as possible through a variety of food. If you need a supplement, vitamins and mineral pills taken at the right time and in the right amount may be helpful.

Before you begin taking any type of supplement, talk to your healthcare provider. They can help you decide if supplements will benefit you.