To function properly, your body needs 13 vitamins — 9 of which are water-soluble and 4 of which are fat-soluble (1).

While these nutrients are found in varying amounts in food, some people need to supplement with certain vitamins to meet their nutritional requirements.

Normally, most vitamins can be taken at any time of day. That said, some vitamins are better absorbed under special conditions, which is why it’s good to know how and when to take a supplement to promote optimal absorption.

This article explains how and when to take vitamins.

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As the name implies, water-soluble vitamins dissolve in water. As such, you don’t need to take them with food for them to be absorbed.

There are nine water-soluble vitamins, which include vitamin C plus the eight B vitamins — B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate), and B12 (cobalamin) (2, 3).

You need to regularly consume water-soluble vitamins because, unlike fat-soluble vitamins, they’re not readily stored in your body’s tissues. Instead, excess water-soluble vitamins are excreted through your urine (4).

Vitamin C

Vitamin C plays many critical roles in your body. For example, it functions as a powerful antioxidant and is needed for immune health, as well as collagen and neurotransmitter synthesis (5).

There are several forms of vitamin C supplements, including ascorbic acid, ascorbic acid with bioflavonoids, liposomal vitamin C, and calcium ascorbate.

Ascorbic acid supplements have a bioavailability similar to that of the ascorbic acid found in foods like fruits and vegetables (6).

You can take vitamin C supplements at any time of day, with or without food, although taking ascorbic acid with foods can help decrease the potential gastrointestinal side effects caused by its high acidity (7).

Make sure to store vitamin C supplements in a cool, dark place, as this nutrient is sensitive to heat and light.

Also, keep in mind that because excess vitamin C is excreted, doses over 1,000 mg typically aren’t needed — except under specific circumstances, such as during high-dose intravenous (IV) vitamin C treatment (8, 9, 10, 11).

B vitamins

B vitamins are sold individually or as B complex supplements that contain all eight B vitamins.

Because they’re water-soluble, you can take them with or without food and at any time of the day. That said, it’s often recommended to take B vitamins in the morning due to their important role in nutrient metabolism and energy production.

What’s more, some people may benefit from taking B vitamins on an empty stomach. For example, it’s recommended that people with a B12 deficiency take B12 supplements on an empty stomach with water to promote maximal absorption (12).

Summary

Water-soluble vitamins are not readily stored in your body, so you must consume them regularly to maintain healthy levels. Water-soluble nutrients can be taken with or without food and at any time of day.

Unlike water-soluble vitamins, fat-soluble vitamins depend on fat for proper absorption. Thus, it’s generally recommended that you take fat-soluble compounds with a meal that contains fat.

Vitamin A

Vitamin A deficiency is rare in the United States but more common in developing countries.

Certain populations are more at risk of developing vitamin A deficiency due to increased needs or reduced absorption. This includes people who are pregnant and breastfeeding and those with cystic fibrosis (13, 14).

Most vitamin A supplements contain vitamin A derived from fish liver oil or in the form of vitamin A carotenoids, which are plant compounds that your body converts into the active form of vitamin A.

To promote optimal absorption, you should take vitamin A supplements with a fat-containing meal.

Keep in mind that if you eat a balanced diet, taking vitamin A supplements typically isn’t necessary.

Plus, some evidence suggests that high-dose vitamin A supplements may increase the risk of all-cause and cancer-related mortality. For this reason, don’t supplement with high-dose vitamin A unless a healthcare provider recommends doing so (15)

Vitamin D

Vitamin D is needed for immune function, bone health, cellular growth, and more. Unfortunately, more than 1 billion people worldwide are deficient in this important nutrient (16).

Vitamin D can be taken at any time of day, and most of these supplements should be taken with fat-containing meals or snacks to ensure optimal absorption.

For example, one study in 50 older adults found that vitamin D absorption was 32% greater in those who took a vitamin D supplement with a fat-containing meal compared with those who took it with a fat-free meal (17).

However, some vitamin D supplements aren’t affected by what you eat. For example, one animal study found that oil-based and microsomal vitamin D supplements — vitamin D encapsulated in fatty acid spheres — can be taken without food (18, 19).

It’s important to note that vitamin D activation depends on having adequate levels of magnesium. Therefore, to maintain healthy vitamin D levels, make sure you’re also getting enough magnesium (20).

Also, keep in mind that certain fat-soluble vitamins, including vitamin E, may affect vitamin D absorption. On the other hand, taking vitamin K alongside vitamin D may benefit bone mineral density (21, 22).

Vitamin E

Vitamin E functions as a major antioxidant in your body and is essential for healthy blood flow and immune function (23).

It’s also a popular dietary supplement — even though this nutrient is found in many foods and deficiency is rare (24).

That said, people who have certain medical conditions, including short bowel syndrome, cystic fibrosis, and Crohn’s disease, may have to supplement with vitamin E to avoid deficiency (24).

It’s typically recommended that vitamin E supplements are taken with a meal. However, one 2019 study in 27 women found that as long as fat was ingested throughout the day, vitamin E was absorbed effectively (25).

This means it may not be necessary to take vitamin E with a fat-containing meal as long as you consume enough fat at subsequent meals.

Keep in mind that even though vitamin E is essential to health, taking too much in supplement form could cause harm in certain populations.

For instance, some research suggests that high-dose vitamin E supplements may lead to an elevated risk of prostate cancer in healthy men (26, 27).

Vitamin K

Vitamin K refers to a family of fat-soluble compounds that includes vitamin K1 (phylloquinone) and vitamin K2 (menaquinones) (28).

Vitamin K is needed for blood clotting, bone and heart health, and more (29).

Clinically significant vitamin K deficiency is rare in adults, although it’s more common in those with bleeding disorders and malabsorption conditions, as well as in people taking medications that interfere with vitamin K absorption.

You can take vitamin K supplements at any time of day with a meal or snack that contains fat.

Because most people get enough vitamin K through their diet, it’s not recommended to take high-dose supplements unless a healthcare provider recommends doing so — even though these supplements are generally safe and not related to significant side effects (28).

Nevertheless, vitamin K supplements may interfere with certain anticoagulant medications. If you’re taking these medications, consult your healthcare provider before taking vitamin K.

If possible, take vitamin K separately from the fat-soluble vitamins E and A. On the other hand, taking vitamins D and K together can be beneficial, as these nutrients work synergistically to promote bone health and healthy calcium levels in your body (30, 31, 32).

Summary

Fat-soluble vitamins play many important roles in your body. Check with your healthcare provider if you have questions about supplementing with these vitamins, as they may not be appropriate for everyone.

Multivitamins typically contain a variety of vitamins and minerals.

Some people prefer multivitamins over single-nutrient supplements because they’re convenient and can be less expensive.

Although data on the long-term health benefits of taking a multivitamin is inconsistent, it’s known that taking them can help fill nutrient gaps, particularly in vulnerable populations like older adults and people who are pregnant (33, 34, 35).

Because these supplements commonly contain both fat- and water-soluble vitamins, it’s typically recommended to consume them with a meal.

This may enhance the absorption of certain nutrients while reducing the risk of gastrointestinal upset, which can otherwise occur when taking a multivitamin on an empty stomach.

If you’re taking two or more pills per day, consider splitting the dose to help your body absorb certain nutrients more effectively. For example, take one pill with breakfast and one with lunch.

If you have questions about dosing or how to take your vitamin supplements, consult your healthcare provider for advice.

Summary

Taking a multivitamin with a meal may help enhance the absorption of certain nutrients and help decrease your risk of digestive issues.

Your body absorbs and stores nutrients in different ways. This should be considered when taking single-nutrient supplements and multivitamins.

For example, some nutrients are better absorbed with meals, while others can be taken on an empty stomach.

If you have questions about dietary supplements, your healthcare provider can provide information on proper dosing and recommend relevant supplements based on your specific health needs.