How Much Vitamin D is Enough?

How Much Vitamin D Should I Take A Day? 

Vitamin D is naturally absorbed through the skin by sunlight (UVB rays) and very few food sources. Depending on various factors, including location, diet, length of exposure to the sun, and skin tone, you may have to take a supplement to get adequate levels of vitamin D. Your doctor can confirm if you need a vitamin D supplement through a blood test.

Vitamin D intake is measured in international units (IU) or micrograms (mcg). One microgram of vitamin D is equal to 40 IU. 

Age-Related Recommendations for Daily Vitamin D Intake

The Office of Dietary Supplements of the U.S. Food and Nutrition Board makes recommendations for dietary reference intakes of nutrients. The recommended dietary allowance (RDA) for vitamin D in people of different ages is as follows: 

• Infants 0–12 months: 400 IU (10 mcg)

• Children 1–18 years: 600 IU (15 mcg)

• Adults up to 70 years: 600 IU (15 mcg)

• Older Adults over 70 years: 800 IU (20 mcg)

• Pregnant or lactating women: 600 IU (15 mcg)

Note: There are no differences between the recommended dietary allowances of vitamin D for males and females.

What is Vitamin D?

Vitamin D, also called calciferol, is a fat-soluble vitamin that promotes healthy bones and teeth. It helps the body absorb calcium, another important nutrient that helps build bones and regulates muscle contractions. Vitamin D also has additional health benefits, such as supporting the nervous system and immune function, regulating insulin levels, promoting heart health, and reducing inflammation.

Sources of Vitamin D

Sunlight Exposure

Vitamin D is called the sunshine vitamin because the body makes vitamin D when skin tissues are exposed to ultraviolet B (UVB) rays in sunlight. However, excessive sunlight exposure can increase the risk of skin cancer. Therefore, it is preferable to obtain vitamin D from dietary sources and vitamin D supplements.

Dietary Sources: What Food is Highest in Vitamin D?

Vitamin D is present in very few foods naturally. Dietary sources of vitamin D3 include animal-origin foods, such as oily and fatty fish (trout, salmon, sardine, mackerel, tuna), beef liver, and egg yolks. Dietary sources of vitamin D2 include plant sources such as mushrooms. Overall, foods with the highest vitamin D content include trout, salmon, and mushrooms. 

Additionally, you can obtain vitamin D from vitamin D-fortified foods such as breakfast cereals, orange juice, and fortified dairy products like milk, yogurt, and cheese. 

Dietary Supplements

Vitamin D is available in supplement form as a liquid, tablet, and capsule. It can also be administered as an injection by a healthcare provider. Many multivitamins contain vitamin D as one of the ingredients. Fish liver oils are a rich source of vitamin D (1 tablespoon of cod liver oil contains 1,360 IU or 34 mcg of vitamin D).

It is best to take supplemental vitamin D with a meal or snack that contains some fat because vitamin D is a fat-soluble vitamin. Check out our blog: “Prescription Vitamin D Vs. Over The Counter.”

Note: Calcium is absorbed from the small intestine when vitamin D is present. Along with phosphorus, calcium plays a critical role in strengthening bones. You need both vitamin D and calcium for healthy bones. It may, therefore, be necessary to take calcium supplements along with a vitamin D supplement.

Optimal Blood Levels of Vitamin D

How Do I Measure My Vitamin D Levels?

Your doctor can check your vitamin D status with a blood test. 

What is the Normal Vitamin D Level?

The normal range of vitamin D that is considered adequate for bone health and overall health is 50 nmol/L or higher (20 ng/mL or higher). 

Vitamin D blood levels:

• Less than 30 nmol/L (12 ng/mL) is vitamin D deficiency. It might be associated with bone problems (rickets in children and osteomalacia in adults).

• Between 30 and 50 nmol/L (12 and 20 ng/mL) indicate vitamin D insufficiency. This is linked to a higher risk of bone problems. 

• Between 50 and 124 nmol/L (20 and 49 ng/mL) is considered healthy.

• Higher than or equal to 125 nmol/L (50 ng/mL) is too high and can cause adverse health effects from vitamin D toxicity.

What are the Health Benefits of Optimum Vitamin D Levels?

Vitamin D is crucial for bone health. In addition, it plays an important role in:

• Modulating cell growth, neuromuscular function, and glucose metabolism.

• Supporting the nervous system and immune function.

• Regulating insulin levels.

• Promoting heart health with blood pressure and cholesterol-lowering effects.  

• Reducing inflammation.

How to Know if You Have Low Vitamin D?

Signs and symptoms of vitamin D deficiency may include fatigue, decreased energy, bone pain, joint pain, muscle pain, muscle weakness, and mood changes such as depression. Vitamin D deficiency is common, and many people are unaware they have low levels. 

Health Risks Associated with Low Vitamin D

Severe vitamin D deficiency can cause rickets in children. This is a condition in which the bones soften and weaken, leading to bent or bowed bones, joint deformities, muscle weakness, and bone pain. 

Prolonged vitamin D deficiency in adults can lead to osteomalacia (bone softening) and osteoporosis (bone weakening). Additionally, not having enough vitamin D in the body can result in low calcium levels and hyperparathyroidism. Also, low vitamin D levels are linked to a range of health problems, including high blood pressure, diabetes, cardiovascular disease, autoimmune problems, neurological diseases, infections, and pregnancy complications. 

Who Is At High Risk of Vitamin D Deficiency?

Certain factors can increase the risk of deficient or insufficient vitamin D (low blood levels of vitamin D in your body).

Reduced Sun Exposure

As noted, vitamin D is made by the body when ultraviolet B (UVB) rays in sunlight are absorbed by the skin tissues. 

• People who live at higher latitudes receive less ultraviolet light exposure and may be prone to vitamin D deficiency or insufficiency. 

• Wearing clothing that covers the arms and legs can limit sun exposure.

• The use of sunscreen with a high sun protection factor (SPF) can potentially affect the skin’s ability to make vitamin D, resulting in less vitamin D in the body.

• Air pollution can scatter UVB rays and reduce vitamin D production in the skin.

• Dark skin has more melanin and needs more UVB light exposure to make the same amount of vitamin D as lighter skin.

• Warm skin temperature promotes vitamin D production. As a result, people living in warm or hot climates make more vitamin D.

Health Conditions

Certain medical conditions are linked to a higher risk of low vitamin D in the body, for example:

• Conditions that affect the digestive system, such as chronic pancreatitis, Crohn's disease, celiac disease, and cystic fibrosis, can decrease vitamin D absorption from the gut.

• Kidney disease and liver disease can lower the availability of enzymes required to convert vitamin D to its active form.

• Obesity (body mass index above 30 kg/m2) is linked to low vitamin D levels. Therefore, obese and overweight individuals may need to take vitamin D supplements to maintain healthy levels of the vitamin in their bodies.

• Bariatric surgery (weight loss surgery) can lead to trouble absorbing vitamin D from the digestive tract as a result of the procedure.

Vitamin D Supplements

What Kind of Vitamin D Should I be Taking?

Vitamin D has two forms—D2 (ergocalciferol) and D3 (cholecalciferol). Both are well absorbed in the small intestine and can help meet your vitamin D requirements. However, D3 might increase your vitamin D level more effectively compared to D2. It is best to consult your doctor to confirm which form is best for your supplementation needs.

Recommended Dosages of Vitamin D Supplements

The general recommendation for adults is to take 600-800 IU of vitamin D daily, depending on age. How much vitamin D you should take every day in the form of dietary supplements will depend on various factors, such as your intake of vitamin D from dietary sources, sun exposure, skin tone, latitude where you live, season, clothing choices, and health conditions. 

Your doctor can measure your vitamin D level with a blood test and tell you whether you need to take a vitamin D supplement. They can also recommend the appropriate dosage of vitamin D supplementation. In addition, your provider can tell you if you need calcium supplementation.

What Are the Effects of Too Much Vitamin D?

Too much vitamin D in the body from vitamin D supplementation can lead to toxicity. Signs and symptoms of excess vitamin D may include nausea, vomiting, decreased appetite, constipation, increased thirst, frequent urination, dehydration, fatigue, muscle weakness, bone pain, lethargy, confusion, and kidney stones. These complications of vitamin D toxicity occur due to hypercalcemia (too much calcium in the blood).

Vitamin D Toxicity

How Much Vitamin D Is Too Much?

Health experts consider 4,000 IU (100 micrograms) per day of vitamin D as the tolerable upper intake level. Anything above 4,000 IU or 100 mcg per day is too much vitamin D for adults and children 12 years of age and older. Children between 1 and 12 years of age should not exceed 2,000 IU (50 micrograms) per day of vitamin D supplements. Infants below 1 year of age should not exceed 1,000 IU (25 micrograms) of vitamin D supplementation per day.

Symptoms of Excessive Vitamin D Intake

Excess vitamin D can cause symptoms such as nausea, vomiting, decreased appetite, muscle weakness, confusion, excessive thirst, frequent urination, dehydration, and kidney stones. 

Dangerously high levels of vitamin D can result in an irregular heartbeat, kidney failure, and even death. 

Note: Very high levels of vitamin D are usually the result of excessive vitamin D supplementation. You don’t get too much vitamin D from sun exposure because your body stops making vitamin D when it has enough.

Common Questions About Dosage of Vitamin D Supplementation

Should I Take 1000 or 2000 Vitamin D?

The recommended amount of vitamin D for adults up to 70 years old is 600 IU (15 micrograms) per day. However, taking vitamin D 1,000 to 2,000 IU per day as a dietary supplement is generally safe for most adults. It can help people with vitamin D deficiency or insufficiency achieve adequate blood levels of this vitamin for health benefits. 

Is It Safe To Take 5000 IU of Vitamin D3 Every Day?

It is not safe to take 5000 IU of vitamin D3 every day. High doses such as 5,000 IU can lead to vitamin D toxicity. The upper safety limit for daily intake is 4,000 IU of vitamin D for adults and children above 12 years of age.