The Worst Time to Take a Vitamin D Supplement

Vitamin D Supplement

Vitamins don’t directly supply the energy that runs your body, but by serving as co-factors, they play a key support function for many aspects of health. The human body needs vitamins and minerals to function, but it can’t produce enough on its own. Instead, you must get them through diet. That’s why it’s so important to make healthy, nutrient-dense food selections rather than dining on ultra-processed foods that contain empty calories.

One vitamin that most people don’t get enough of is vitamin D, the sunshine vitamin. It’s called the sunshine vitamin because the best natural source of vitamin D is exposing your skin to sunlight. When sunlight hits your skin, ultraviolet rays convert a compound on your skin to a precursor of vitamin D. Then, your liver and kidneys activate this pre-vitamin D compound and transform it into an active form your body can use.

Since food isn’t a good source of vitamin D, except for fatty fish, egg yolks, and foods fortified with vitamin D, and not everyone gets enough sunlight, vitamin D deficiency is common. The National Health and Nutrition Examination Survey 2005 to 2006 found that 41% of Americans are deficient in vitamin D.

The Role of Vitamin D in Health and Wellness

Why do you need vitamin D? It helps maintain strong bones, teeth, muscles, and tissue. It also helps your digestive tract absorb calcium and phosphorus for bone health. Research also suggests that vitamin D plays a role in a healthy immune system. Some research suggests that people who are deficient in vitamin D get more colds and upper respiratory infections than those with a healthy vitamin D level. However, it’s not clear whether this is a cause-and-effect relationship.

With such a high rate of deficiency and the important functions of vitamin D, it’s not surprising that many people take a vitamin D supplement. However, not everyone is taking it correctly or at the right time. In fact, there’s a best time and way to take a vitamin D supplement and a worst time.

When Should You Take a Vitamin D Supplement?

The best time to take a vitamin D supplement is with a meal. Vitamin D is a fat-soluble vitamin, meaning you won’t absorb as much of it if you don’t consume it with a source of fat. Vitamin D, being dissolvable in fat, needs to be paired with a fatty food for your gut to absorb it. So, the worst way to take vitamin D is on an empty stomach.

According to a 2010 study, taking vitamin D with the largest meal of the day boosts absorption of this fat-soluble vitamin and makes it more available to your body. Otherwise, it could pass right through you. When researchers measured serum levels of active vitamin D, taking the vitamin with the day’s largest meal led to a 50% increase in absorption. So, pop your vitamin D supplement with the day’s largest meal and make sure that meal contains a source of fat.

The Worst Time to Take a Vitamin D Supplement

The worst time to take a vitamin D supplement is in the evening. The reason? Research shows that taking vitamin D in the after dinner or in the evening may reduce melatonin release, a hormone that rises as the day draws to a close. A small gland called the pineal gland in your brain produces melatonin, a hormone with several functions. It regulates the body’s internal biological clocks and the sleep-wake cycle but also functions as an antioxidant. Studies show low levels of melatonin may contribute to insomnia and jet lag. As an antioxidant, it also helps protect cells from free radical damage.

Some studies show taking vitamin D in the evening makes it harder to fall asleep and reduces sleep quality. Although it’s not clear whether the poor sleep people who take vitamin D later in the day experience comes from imbalances in melatonin, it’s best to take your vitamin D supplement during daylight hours. If you eat a large breakfast or early lunch, add a source of fat and take your vitamin D supplement then.

Now you know how to time your vitamin D supplement and why it’s important to take it with a meal that contains fat. If you’re not sure where you stand with vitamin D, ask your physician to check your vitamin D level via a blood test. Based on your level, they can tell you whether you need a vitamin D supplement and how much you should take to optimize your level.

It’s important not to take large doses without tracking your blood level since high doses of vitamin D over an extended period can be harmful. Experts say that most people can take 1,000 to 2,000 international units (IU) of vitamin D safely and are probably safe with a daily dose as high as 4,000 IU but talk to your physician before taking this quantity. You don’t need that much unless you’re vitamin D deficient.


  • Mulligan GB, Licata A. Taking vitamin D with the largest meal improves absorption and results in higher serum levels of 25-hydroxyvitamin D. J Bone Miner Res. 2010 Apr;25(4):928-30. doi: 10.1002/jbmr.67. PMID: 20200983.
  • Forrest KY, Stuhldreher WL. Prevalence and correlates of vitamin D deficiency in US adults. Nutr Res. 2011 Jan;31(1):48-54. doi: 10.1016/j.nutres.2010.12.001. PMID: 21310306.
  • Jung YS, Chae CH, Kim YO, Son JS, Kim CW, Park HO, Lee JH, Shin YH, Kwak HS. The relationship between serum vitamin D levels and sleep quality in fixed day indoor field workers in the electronics manufacturing industry in Korea. Ann Occup Environ Med. 2017 Jun 24;29:25. doi: 10.1186/s40557-017-0187-7. PMID: 28652922; PMCID: PMC5482959.
  • “Can Vitamin D Lower the Risk of Respiratory Infections?.” 22 Jun. 2020, verywellhealth.com/can-vitamin-d-prevent-respiratory-infections-4842761.
  • “Vitamin D supplementation to prevent acute respiratory ….” pubmed.ncbi.nlm.nih.gov/28202713/.
  • National Institutes of Health. “Vitamin D”

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