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Some supplements and medications come with specific instructions on when and how to take them, while others you simply need to remember to take every day. But which category does vitamin D fall into? Turns out, determining the best time to take vitamin D isn’t quite so simple.
Vitamin D, a.k.a. calciferol, is a fat-soluble vitamin that plays many critical roles in the body. In addition to being found naturally in a few foods (and added to some others), it’s also available as a dietary supplement and is produced by your body from exposure to UV rays, in a process known as vitamin D synthesis, per the National Institutes of Health (NIH).
The benefits of getting enough vitamin D include:
Meet the experts: Keri Gans, M.S., R.D., registered dietitian and author of The Small Change Diet; Jessica Cording, R.D., author of The Little Book of Game Changers
Here, dietitians share the most important factors to keep in mind if you’re supplementing with vitamin D, including the best time to take it, whether to take it with food, and other considerations when choosing the best vitamin D supplement.
When is the best time to take vitamin D?
The short answer: It depends. Because vitamin D is fat-soluble, it’s important to take it with food to enhance absorption, said Jessica Cording, R.D., author of The Little Book of Game Changers. “For many people, that means taking it with a meal,” she added. Beyond that, Cording suggested taking your vitamin D whenever you remember to take it.
If you prefer to take supplements in the evening, keep in mind that there is some mixed research around vitamin D’s impact on sleep. Some older data suggests that vitamin D may impact your body’s production of melatonin, which is a hormone that your brain produces in response to darkness and helps with the timing of your circadian rhythm. However, Cording pointed to newer studies that suggest that maintaining adequate levels of vitamin D may actually help promote good sleep in people who are struggling. “Sometimes if I’m working with somebody who is dealing with sleep disturbances, I’ll have them shift to taking vitamin D at dinner,” she said.
Basically, you can tinker with the timing and see how you feel—increasing your serum concentration of vitamin D (or how much is available in your blood) is the most important thing.
Who should supplement with vitamin D?
If you think you might benefit from a vitamin D supplement, Cording said it’s a good idea to talk to a healthcare provider before adding it to your routine. “The gold standard is really to get blood work done to see where you’re at,” she said. But Cording also pointed out that a large portion of the population doesn’t get adequate amounts of this vitamin.
While it’s still best to talk to a healthcare professional first, Cording said that the following groups are the most likely to benefit from a vitamin D supplement:
People who live in cold climates or are indoors a lot (they’re not getting a lot of vitamin D from sunlight)People with darker skin tones (increased melanin levels in the skin reduce natural production of vitamin D3)Older adults (the skin’s ability to naturally produce vitamin D3 decreases with age)People with medical conditions that impact fat absorption (since vitamin D is fat-soluble)People who eat a plant-based diet (since many vitamin D sources are from animal-based foods)How to choose a vitamin D supplement
When you’re shopping for a supplement, you’ll find two possible sources of vitamin D: Vitamin D2 and vitamin D3. Vitamin D2 comes from fortified foods and mushrooms, while vitamin D3 is produced in the skin when exposed to sunlight and is also found in animal-based foods, per the NIH.
Between the two, Cording suggested choosing vitamin D3. “It’s the most absorbable form,” she said. Keri Gans, M.S., R.D., a registered dietitian and author of The Small Change Diet, agreed. “I would opt for vitamin D in the form of D3 (cholecalciferol) which is more readily available to the body compared to D2 (ergocalciferol),” she said.
Cording also suggested looking for vitamin D3 supplements that also contain vitamin K2. “It enhances the absorption even more,” she explained.
How much should you take? The best way to get the right vitamin D dosage is to get a blood test to measure your serum vitamin D levels and to go from there, Cording said.
People who are on the lower end of normal or just below normal may benefit from taking 5,000 to 10,000 IU of vitamin D, according to Cording. Others may do well with 1,000 IU, while Cording said those who are truly deficient may need to take prescription-strength vitamin D. (But, again, that’s something you should address with your doctor.)
If you are 70 years and older, your daily dose should be closer to 800 IU, noted Gans.
Can you take too much vitamin D?
Too much vitamin D can be toxic, making it important not to have too much. So, it’s important to consult a physician before adding supplements to your diet. Vitamin D increases the absorption of calcium in your body, and having too much of it can cause high levels of calcium to circulate in your blood, per the NIH.
That can lead to symptoms like nausea, vomiting, muscle weakness, mental health disturbances, pain, loss of appetite, dehydration, peeing a lot, feeling overly thirsty, and developing kidney stones, according to the NIH. In severe cases, having too much vitamin D may lead to kidney failure, heart issues, and even death. However, the NIH also notes that most adults can tolerate up to 4,000 IU of vitamin D per day without any risks.
Top foods rich in vitamin D
Vitamin D is more commonly found in animal products, like certain types of fish and fortified dairy products, per Cording.
These are foods high in vitamin D, according to the NIH:
Cod liver oil, 1 Tbsp, 34 mcgRainbow trout, 3 oz, 16.2 mcgSockeye salmon, 3 oz, 14.2 mcgWhite raw mushrooms, ½ cup, 9.2 mcg2% vitamin D fortified milk, 1 cup, 2.9 mcgFortified cereal, 1 serving, 2 mcgEgg, 1 large scrambled, 1.1 mcg
Again, if you’re concerned about your vitamin D intake, talk to your healthcare provider. They can do the necessary evaluations to help you make an informed decision about supplementation.
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. Also, be careful about giving supplements to a child, unless recommended by their healthcare provider.
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