Vitamin D is an essential nutrient that plays many important roles in the body. It helps regulate calcium and phosphate absorption to maintain healthy bones. Vitamin D also supports immune function, cardiovascular health, and much more.
Vitamin D3 (cholecalciferol) is one of the two major forms of vitamin D, along with vitamin D2 (ergocalciferol). Vitamin D3 is produced in the skin when it is exposed to sunlight. It can also be obtained through the diet from foods like fatty fish, egg yolks, and fortified foods like milk and cereal. Vitamin D3 supplements are widely available as an over-the-counter vitamin supplement.
Recommended Vitamin D Intake
The recommended daily allowance (RDA) for vitamin D is:
- 600 IU (15 mcg) per day for adults up to age 70
- 800 IU (20 mcg) per day for adults over 70
Many experts suggest that these recommendations are too low, and that higher intakes in the range of 1000-4000 IU per day are needed for optimal health. However, the safe upper limit is set at 4000 IU per day for adults.
Can You Take Too Much Vitamin D3?
Yes, it is possible to take too much vitamin D3. Consuming extremely high amounts from supplements long-term can lead to a condition called vitamin D toxicity or hypervitaminosis D.
Signs and symptoms of vitamin D toxicity may include:
- Nausea, vomiting, poor appetite
- Increased urination and thirst
- Constipation
- Fatigue, weakness
- Confusion
- Irregular heartbeat
- High blood pressure
- Kidney stones
- Bone loss, fractures
- Calcification of soft tissues like kidneys and arteries
Causes of Vitamin D Toxicity
Taking too much vitamin D3 from supplements long-term is by far the most common cause of vitamin D toxicity. This occurs mostly with extremely high dose regimens above 10,000 IU per day taken for months to years.
Other potential causes include:
- Eating excessive amounts of fortified foods enhanced with vitamin D like cereal if consumed regularly
- Consuming foods that contain extremely high amounts of vitamin D like certain fish oils and liver
- Medical conditions that increase sensitivity to vitamin D like certain lymphomas, sarcoidosis, tuberculosis, and kidney disease
- Interactions with certain medications that affect vitamin D metabolism
Getting excessive sun exposure does not cause vitamin D toxicity because the body is able to regulate production.
Can You Take Too Much Vitamin D3 at One Time?
Taking a single, extremely large dose of vitamin D3 such as 100,000 IU in one day can potentially cause vitamin D toxicity. However, acute toxicity from a single high dose is very rare.
Signs of acute vitamin D toxicity may show up within hours or days. Symptoms include nausea, vomiting, weakness, and frequent urination. But toxic effects are unlikely with doses under 200,000 IU.
Instead, vitamin D toxicity is almost always caused by consistently taking doses above 10,000 IU per day for long periods of time such as months or years.
Factors That Affect Vitamin D Toxicity Risk
Some factors can increase or decrease the risk of vitamin D toxicity at certain doses:
- Body weight – Toxicity risk increases with lower body weight
- Age – Older adults are at higher risk
- Health conditions – Diseases like kidney disease, tuberculosis, lymphoma increase sensitivity
- Medications – Drugs that affect vitamin D metabolism like steroids may increase risk
- Magnesium status – Low magnesium increases risk as magnesium helps regulate vitamin D
- Vitamin K status – Low vitamin K is associated with increased risk of toxicity
What Dose of Vitamin D3 is Too Much?
Doses over 10,000 IU per day taken consistently over time are most commonly associated with toxicity. The table below summarizes the doses considered possibly unsafe:
| Age | Possibly Unsafe Dose Per Day |
|---|---|
| 0 – 12 months | Over 1,000 IU |
| 1 – 3 years | Over 2,500 IU |
| 4 – 8 years | Over 3,000 IU |
| 9+ years | Over 4,000 IU |
However, lower doses around 4,000 IU per day have the potential to cause adverse effects in very sensitive individuals. And doses over 20,000 IU per day greatly increase toxicity risk for all adults.
The Food and Nutrition Board set the tolerable upper intake level (UL) for vitamin D per day at:
- 1,000 IU for infants
- 2,500 IU for children aged 1-3 years
- 3,000 IU for children aged 4-8 years
- 4,000 IU for children and adults aged 9 years and older
Intakes above the UL may cause adverse health effects over the long-term. However, these ULs are set conservatively and many experts argue intakes of 10,000 IU or more per day are safe for most people if only done for short periods of time such as a few months.
Maximum Single Dose of Vitamin D
In terms of single doses, the Endocrine Society provides the following guidance:
- Adults: Up to 10,000 IU is likely safe as a single dose.
- Children ages 9+: Up to 5,000 IU is likely safe as a single dose.
- Younger children: Up to 1,000 IU for ages 1-3 and 2,000 IU for ages 4-8 is likely safe as a single dose.
Larger single doses above these general cutoffs may potentially cause acute toxicity in some individuals.
Can You Safely Take High Doses of Vitamin D3 Short-Term?
While extremely high doses of vitamin D3 above 10,000 IU per day can cause toxicity when taken consistently long-term, most evidence suggests that short-term daily doses up to 10,000 IU are safe for most adults.
Many studies use short-term doses up to 10,000 IU of vitamin D3 daily for 1-5 months with no adverse effects. And temporary high-dose regimens are sometimes medically prescribed to correct vitamin D deficiency.
For example, the Endocrine Society recommends vitamin D repletion dosing regimens for deficiency of:
- 6,000 IU per day for 8 weeks for adults to correct deficiency
- Up to 4,000 IU per day for pregnant women for at least 6-12 weeks to replenish stores
So evidence supports short-term daily doses up to 10,000 IU for a period of several months as generally safe for most healthy adults. But long-term intake at this level without medical supervision may increase toxicity risk.
High-Dose Vitamin D3 Supplements
Given that short-term daily vitamin D3 intake up to 10,000 IU appears relatively safe for most, high-dose vitamin D3 supplements within this range are readily available including:
- 5,000 IU vitamin D3 tablets or capsules
- 10,000 IU vitamin D3 softgels
These high-dose supplements may be appropriate for short periods of time if advised by your healthcare provider for correcting deficiency. But they should not be taken long-term or without medical monitoring.
Signs of Vitamin D Toxicity
Signs and symptoms of vitamin D toxicity may include:
- Nausea, vomiting, loss of appetite
- Increased thirst and urination
- Constipation
- Fatigue, weakness, drowsiness
- Confusion
- Muscle or bone pain
- Irregular heartbeat
- High blood pressure
- Kidney stones
- Bone loss, fractures
- Calcification of soft tissues
Symptoms may develop over months to years with chronic excessive intake. Signs of acute toxicity from a single high dose may occur rapidly within hours or days.
Seek medical attention if you experience any concerning symptoms related to vitamin D supplementation. A blood test can check your vitamin D level.
Treatment for Vitamin D Toxicity
Treatment for vitamin D toxicity involves stopping all supplemental vitamin D. Additional treatment may include:
- Restricting dietary calcium
- Increasing hydration to promote urination and clear excess vitamin D
- Medications like steroids or bisphosphonates
- Dialysis in severe cases
With treatment, symptoms usually resolve over weeks to months as excess vitamin D is cleared from the body.
Ways to Prevent Vitamin D Toxicity
You can take the following precautions to prevent vitamin D toxicity:
- Avoid exceeding 10,000 IU per day from supplements long-term without medical supervision
- Take the lowest dose needed to correct deficiency if prescribed short-term high-dose vitamin D
- Read supplement labels carefully and avoid excessive fortified foods
- Get blood levels tested if taking high doses to monitor levels
- Maintain adequate magnesium and vitamin K intake to support vitamin D metabolism
- Use sunscreen as needed to avoid excessive sun exposure
Who is at Higher Risk for Vitamin D Toxicity?
Some people are at increased risk of vitamin D toxicity at a given dose level compared to others. Higher risk groups include:
- Older adults over age 70
- Individuals with low body weight
- People with medical conditions including sarcoidosis, tuberculosis, lymphoma, and kidney disease
- People taking certain medications that interact with vitamin D metabolism
- People with low magnesium levels
- People with low vitamin K status
Those at higher risk may need to be more cautious about vitamin D intake and have blood levels monitored.
Special Considerations for Infants and Children
Infants, children and adolescents require lower vitamin D doses than adults. Too much can affect growth and bone development.
The Food and Nutrition Board set more conservative UL cutoffs for vitamin D intake in these younger age groups:
- 1,000 IU per day for infants 0-12 months
- 2,500 IU per day for children 1-3 years
- 3,000 IU per day for children 4-8 years
Doses above the tolerable upper limit increase risk of toxicity over time in children. Hypercalcemia and calcification of soft tissues like kidneys have occurred, especially in infants given high doses like over 1,000 IU per day consistently.
So it is very important not to exceed age-specific dose recommendations for infants and children. Unless prescribed by a doctor, vitamin D supplementation is typically unnecessary for healthy, breastfed infants.
Vitamin D Toxicity During Pregnancy and Breastfeeding
The Food and Nutrition Board set the UL for vitamin D at 4,000 IU per day for pregnant or lactating women, the same as for other adults.
While vitamin D requirements do increase during pregnancy and breastfeeding, excessive intake above 4,000 IU per day may cause hypercalcemia and other toxic effects in the mother. High doses can also lead to excessive vitamin D levels in breast milk which may harm the infant.
Routine vitamin D supplementation is not necessary during pregnancy or lactation. If deficiency is diagnosed by a doctor, no more than the recommended treatment dose should be taken.
Conclusion
In summary, vitamin D toxicity is primarily associated with long-term intake of extremely high amounts over 10,000 IU per day from supplements. Short-term daily doses up to 10,000 IU for several months appear relatively safe for most adults.
However, the safe upper limit is lower for infants and children. And certain medical conditions, medications, and individual factors can increase risk of toxicity at a given dose.
Signs of vitamin D toxicity may take months or years to show up. Seek medical attention if you experience any concerning symptoms related to high-dose supplementation.
To avoid negative effects, do not exceed the tolerable upper intake levels for your age group without medical supervision. Have blood vitamin D levels monitored if taking high therapeutic doses to correct deficiency.