Vitamin D dosage, forms, and strengths

Vitamin D is an essential nutrient normally produced by the body when the skin is exposed to the sun’s rays. People can also get vitamin D from certain foods like fatty fish (sardines or salmon), enriched foods like milk or cereal, or over-the-counter supplements or multivitamins. The body needs vitamin D for calcium absorption. The body needs calcium to maintain bone health, nerve function, muscle strength, and immune function. Chronic vitamin D deficiency can lead to health problems such as weak bones, fractures, muscle weakness, bone pain, a weakened immune system, and high blood pressure (hypertension). 

Vitamin D supplements contain either vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol) and can be purchased over the counter. However, healthcare professionals may prescribe high-dose vitamin D supplements (usually vitamin D3) or active vitamin D (calcitriol) for vitamin D deficiency, underactive parathyroid glands, and rickets. 

Vitamin D forms and strengths

Over-the-counter vitamin D supplements can be found in various formats. Prescription high-dose vitamin D comes in six formats:

• Capsules: 400 International Units (IUs), 1,000 IUs, 2,000 IUs, 5,000 IUs, 10,000 IUs, 50,000 IUs

• Tablets: 400 IUs, 1,000 IUs, 2,000 IUs, 3,000 IUs, 5,000 IUs

• Orally-disintegrating tablets: 1,000 IUs

• Chewable tablets: 400 IUs, 1,000 IUs

• Oral solution: 400 IUs per milliliter (mL), 5,000 IUs/mL, 2,000 IUs/0.16 mL

• Spray: 1,000 IUs per actuation

40 International Units is equal to 1 microgram of vitamin D, so a 400 IU dose is equal to 10 mcg of vitamin D. 

Vitamin D dosage for adults

People often choose to take store-bought vitamin D supplements to prevent vitamin D insufficiency or to enjoy the healthy benefits of vitamin D. Health professionals may prescribe or suggest OTC vitamin D to prevent vitamin D deficiency. Prescription-strength vitamin D supplements are used to treat vitamin D deficiency and hypoparathyroidism. Healthcare professionals may also prescribe it off-label to treat bone softening (osteomalacia).

As a nutritional supplement, the recommended daily allowance (RDA) of vitamin D is the standard dose. Healthcare providers may advise higher doses for people with certain medical conditions, such as chronic kidney disease or problems with the intestine absorbing fat (malabsorption). Health professionals also prescribe vitamin D supplements to people with cystic fibrosis. Cystic fibrosis causes poor fat absorption in the intestines. Vitamin D is a fat-soluble vitamin, so vitamin D insufficiency is a common complication of cystic fibrosis. Vitamin D is also commonly prescribed with calcium supplements to prevent osteoporosis. 

• Standard adult dosage for nutritional supplementation: 600 IUs (15 mcg) per day in younger adults OR 800 IUs (20 mcg) per day for older adults 

• Standard adult dosage for cystic fibrosis nutritional supplementation: 800–2,000 IUs of vitamin D3 per day

• Standard adult dosage for osteoporosis prevention nutritional supplementation: 800 IUs per day along with daily calcium supplements

Vitamin D dosage for vitamin D deficiency

Vitamin D deficiency occurs when blood levels of vitamin D are too low. Low vitamin D levels are common, but children, nursing home residents, people with excess weight, people who stay indoors, or people who use sunscreen are particularly at risk. Vitamin D deficiency is diagnosed when a blood test shows concentrations below 30 nanograms per milliliter. For people with high vitamin D deficiency risk factors—obesity, malabsorption, or use of certain medications—daily doses will be higher. Healthcare providers will recheck vitamin D status during treatment with another blood test. Lower maintenance doses will be used once vitamin D levels exceed 30 ng/mL.

• Standard adult dosage for vitamin D deficiency: 50,000 IUs taken once per week for eight weeks OR 6,000 IUs taken daily for eight weeks

• Standard dosage for vitamin D deficiency in high-risk adults: 6,000–10,000 IUs taken daily for eight weeks

• Standard adult maintenance dosage for vitamin D deficiency: 1,000–2,000 IUs taken daily OR 3,000–6,000 IUs taken daily for high-risk adults

Vitamin D dosage for hypoparathyroidism

Parathyroid hormone deficiency, also called hypoparathyroidism, is a condition in which the parathyroid glands do not produce enough parathyroid hormone. This results in low calcium levels and high phosphate levels. To help normalize calcium levels, healthcare providers prescribe vitamin D supplements. The most effective form is calcitriol capsules. Calcitriol is the “active” form of vitamin D called 25-hydroxyvitamin D. The other option is to take massive doses of vitamin D2 or D3. 

• Standard adult dosage for hypoparathyroidism: 0.25 mcg of calcitriol (active vitamin D) taken once per day OR 50,000–200,000 IUs of vitamin D2 or D3 daily

Vitamin D dosage for children

Vitamin D can be given to children as a nutritional supplement, but healthcare providers may prescribe vitamin D to children for vitamin D deficiency, hypoparathyroidism, or rickets (bone softening), or hereditary high cholesterol.

Nutritional supplementation

• Vitamin D nutritional supplementation for children and adolescents: 600 IUs (15 mcg) per day

• Vitamin D nutritional supplementation for infants and newborns: 400 IUs (10 mcg) per day

Vitamin D deficiency

• Standard vitamin D dosage for vitamin D deficiency in newborns: 1,000–2,000 IUs (25–50 mcg) per day OR 50,000 IUs (1,250 mcg) once per week

• Standard vitamin D dosage for vitamin D deficiency in children <1 year old: 1,000–5,000 IUs (25–125 mcg) per day OR 50,000 IUs (1,250 mcg) once per week

• Standard vitamin D dosage for vitamin D deficiency in children 1–18 years old: 2,000–5,000 IUs per day OR 14,000–50,000 IUs once per week

Hypoparathyroidism

• Standard vitamin D (calcitriol) dosage for children ages 1 month to 2 years old: 0.01–0.015 mcg per day

• Standard vitamin D (calcitriol) dosage for children ages 3–18 years old: 0.25 mcg per day

Rickets

• Standard vitamin D dosage for rickets in newborns: 1,000 IUs (25 mcg) per day for two to three months

• Standard vitamin D dosage for rickets in children <1 year old: 1,000–5,000 IUs (25–125 mcg) per day for two to three months

• Standard vitamin D dosage for rickets in children 1–18 years old: 2,000–20,000 IUs per day for four to eight weeks

Familial hypercholesterolemia (hereditary high cholesterol)

• Standard vitamin D dosage for familial hypercholesterolemia in children 1–17 years old: 800–1,200 IUs (20–30 mcg) per day OR 600,000 IUs (15,000 mcg) every two months

Vitamin D dosage restrictions

There are no vitamin D dosage restrictions for people with kidney problems, hepatic impairment, or other medical issues.

Vitamin D dosage for pets 

Both dogs and cats get most of their vitamin D from their diet rather than sun exposure. Most commercial pet foods should provide adequate pet vitamin D intake, but you should always check the labels. Veterinarians will test vitamin D levels in some pets. When those levels are too low, the standard treatment is to add vitamin D-rich foods to the diet, such as fish oils. Veterinarians can prescribe vitamin D supplements in capsule, tablet, or chewable tablet form. As with humans, hypoparathyroidism in dogs is treated with large quantities of vitamin D supplements. Depending on the weight of the dog, 25,000 to 50,000 IUs of vitamin D are given each day. Doses are lowered when calcium levels return to normal.

How to take vitamin D

Vitamin D is taken like any other dietary supplement. It can be taken any time of day with or without food.

• Take vitamin D supplements as directed by a healthcare provider or package instructions.

• Do not exceed the dose prescribed or advised.

• Ask the prescriber what to do if a dose of prescription vitamin D is missed.

• For vitamin D oral liquid, use the dropper that comes with the supplement to measure each dose.

Vitamin D dosage FAQs

How long can you take vitamin D?

There is no limit to how long people can take vitamin D at the recommended daily allowances. However, prescription-strength vitamin D is usually only used for a limited amount of time. Clinicians will regularly check vitamin D status and reduce the dose when treatment goals are met.

How do I stop taking vitamin D?

Vitamin D can be stopped without side effects. However, talk to your healthcare provider before stopping recommended supplements.

What is the maximum dosage for vitamin D?

Continually taking doses of vitamin D that are more than the recommended amount can cause health problems. Healthcare professionals use the Tolerable Upper Intake Level (UL) standard. It’s the highest daily dose of a vitamin that healthy people can take without causing problems. For vitamin D, that’s 4,000 IUs (100 mcg) for adults, teens, and older children unless recommended for specific medical conditions. 

Can you overdose on vitamin D?

Taking too much vitamin D over time can result in vitamin D poisoning, a serious medical condition that results in hypercalcemia—too much calcium in the blood. Vitamin D toxicity usually takes a long time to develop. Symptoms of chronic vitamin D overuse include gastrointestinal complaints, frequent urination, and excessive thirst. The most concerning symptoms include confusion, lethargy, mood changes, heartbeat irregularities, and coma. 

Is it safe to take vitamin D during pregnancy?

Pregnant women can safely supplement their diet by taking the recommended daily allowance of vitamin D. A healthcare provider may suggest vitamin D supplementation. High-dose vitamin D supplements are not recommended during pregnancy because of the risks to the fetus. These include vitamin D poisoning, cardiovascular defects, and developmental delay. 

Is it safe to take vitamin D while breastfeeding?

People who breastfeed can take the recommended daily allowance of vitamin D. However, that is not enough to provide the daily recommended allowance of vitamin D to the infant, so a breastfed infant should get a vitamin D supplement. Vitamin D doses for people who are breastfeeding and infants shouldn’t exceed the clinician’s recommendations. Excess vitamin D may cause high blood calcium in the infant.