Vitamin D supplements: How much you should take each day, according to dietitians

• The recommended daily intake of vitamin D is 600 IU a day, but some people may need up to 3000 IU.
• You can get vitamin D through foods, sunlight, and supplements.
• If you want to take a vitamin D supplement, talk to your doctor who can find the right dose for you.

Getting enough vitamin D is essential to your overall health since it reduces inflammation, supports immunity, and helps your body absorb calcium, which is needed to build and maintain healthy bones.

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However, despite its importance, vitamin D deficiency is common, and studies suggest over 50% of the population has insufficient levels of this essential nutrient. Therefore, it's not unreasonable to wonder if you're getting enough vitamin D.

Here's what you should know about taking a vitamin D supplement.

How much vitamin D do I need?

While your vitamin D needs change as you age, in general, the average adult needs 600 international units (IU)of vitamin D per day.

If you aren't sure you're getting enough vitamin D through foods, Ryan Andrews, RD, principal nutritionist and adviser at Precision Nutrition, suggests spending some time in the sun.

"Many people can meet their vitamin D requirements through sunshine alone," Andrews says. "A good general guideline is to get about 10 to 20 minutes a day of the midday sun, with face, arms, hands, and legs uncovered."

Warning: Avoid prolonged sun exposure, which is about 30 minutes, because UVB rays also cause sunburns and photodamage, increasing the risk of skin cancer. You should also always wear sunscreen to further protect your skin from damage.

However, certain people may not be able to properly produce or absorb vitamin D, placing them at an increased risk of deficiency, including:

• People who live far from the equator
• People who are frail, housebound, or have jobs that limit their sun exposure
• People who wear clothes that cover up the majority of their skin
• Breastfed infants who don't receive a vitamin D supplement
• Older adults
• People with dark skin, since the pigment, melanin, in dark skin partially blocks the absorption of the sun's UV radiation.
• People with conditions that limit fat absorption, because vitamin D is fat-soluble
• People who are obese
• People who have undergone gastric bypass surgery, because part of the small intestine, which absorbs vitamin D, is removed

How much vitamin D should I take?

If you fall into one of the above categories, you may need to take a vitamin D supplement. While the current RDA for vitamin D is 600 IU per day for adults, studies suggest that you may need to supplement around 3000 IU per day to achieve proper blood levels of vitamin D.

If you think you should take a vitamin D supplement, get your vitamin D levels checked by a physician first. They will perform a 25-hydroxyvitamin D test, which indicates the total amount vitamin D in your system (from the sun, food, and supplements), says Ryan Andrews, RD, principal nutritionist and adviser at Precision Nutrition. This will help them determine the right vitamin D supplement dosage for you.

Important: Vitamin D supplements come in two forms: D3 and D2. Studies suggest D3 may be more efficient at raising your vitamin D blood levels, but vegans should choose D2 supplements since they do not contain any animal by-products.

Can you take too much vitamin D?

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Unlike some vitamins, it is possible to take too much vitamin D.

Vitamin D toxicity is a dangerous condition that is more likely if you take high-dose vitamin D supplements over a long period of time.

Toxicity is unlikely if you take less than 10,000 IU of vitamin D per day, but cases have been reported in adults taking doses ranging from 50,000 to 60,000,000 IU per day over the course of multiple weeks. Most of these cases were due to supplement doses being improperly labeled.

Since vitamin D increases calcium absorption, an excess amount can lead to hypercalcemia - a rare condition where calcium levels in the blood are above normal, says David Buchin, MD, Director of Bariatric Surgery at Northwell Health-Huntington Hospital.

Signs of hypercalcemia include:

• Nausea and vomiting
• Muscle weakness
• Neuropsychiatric disturbances
• Pain
• Loss of appetite
• Dehydration
• Polyuria
• Excessive thirst
• Kidney stones

In extreme cases, vitamin D toxicity can cause renal failure, soft tissues calcification, cardiac arrhythmias, and death.

Insider's takeaway

Vitamin D deficiency is a global health problem. Therefore, some people may choose to use supplements to meet their daily vitamin D needs. If you're considering a supplement, talk to your doctor who may want to check your vitamin D levels to determine the proper dose.

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