The maximum safe dose of vitamin D is 4,000 IU a day. However, high dosages of 10,000 IU from supplements may be beneficial in cases of acute vitamin D deficiency.
Health benefits of vitamin D
Vitamin D is necessary for many other functions of the human body. Vitamin D deficiency has been linked to increased risk of hair loss, dry skin & wrinkles, osteoporosis, cancer, cardiovascular disease, depression, multiple sclerosis, diabetes, obesity, decreased testosterone levels, and constipation.[1]
How much vitamin D do we need daily?
The recommended daily intake of vitamin D for most adults is 600 IU. Elderly people should take a higher dosage of 800 IU per day.
What’s the normal range of vitamin D in the blood?
Vitamin D levels in the blood should be between 50-75 nmol/L or 20-30 ng/mL.
| nmol/L | ng/mL | Health status |
| less than 30 | less than 12 | severe deficiency |
| between 30-50 | between 12-20 | inadequate |
| between 50-125 | between 20-50 | adequate |
| higher than 125 | higher than 50 | potential side effects |
| higher than 150 | higher than 60 | may cause toxicity |
What’s the maximum safe dose of vitamin D?
The maximum safe dose of vitamin D for adults and teenagers is 4,000 IU, or 100 mcg per day.
The maximum safe dosage for kids of 4–8 years is 3,000 IU. Babies and newborns shouldn’t consume more than 1,500 and 1,000 IU of vitamin D per day, respectively.
You should regularly check serum 25(OH)D levels if you take vitamin D supplements. Even serum levels above 75–120 nmol/L (30–48 ng/mL) may cause side effects.
If you have much lower serum 25(OH)D levels, you can get much higher vitamin D dosages, though. Even dosages of 10,000 IU are considered safe. They have low risk of toxicity.[2]
After all, most vitamin D supplements contain between 2,000 and 5,000 IU of vitamin D per tablet. You can compare prices between a wide variety of vitamin D supplements on iHerb.
Always consult your physician before taking vitamin D supplements.
Is it better to take vitamin D every day or once a week?
Taking vitamin D supplements every day is the most effective way to increase your serum vitamin D levels. Supplementation once a week or once a month is less effective.[3]
Furthermore, weekly vitamin D dosages of up to 100,000 IU are considered pretty safe, for treating acute vitamin D deficiency. In a study, vitamin D supplementation for a year with this dosage didn’t cause vitamin D toxicity.[4]
How many times a week should I take vitamin D?
If you have severe vitamin D deficiency, you may need higher daily dosages of vitamin D. After a few months, you’ll probably need to decrease the daily dosage, in order, to prevent vitamin toxicity.
So, if you have serum vitamin D levels less than 20 ng/mL, you could take 10,000 IU of vitamin D every day for 1-2 months. Then, check your vitamin D levels in your blood. If your vitamin D levels in the blood are above 30 ng/mL, you can limit your daily vitamin D dose to 4,000 IU, which is the maximum safe daily dosage.
You may even have to skip vitamin D supplementation. Especially, if you have serum vitamin D levels above 50 ng/mL.
Side effects of too much vitamin D from supplements
Too much vitamin D may increase calcium levels in the blood. Side effects, such as nausea, vomiting, muscle weakness or pain, loss of appetite, dehydration, thirst, and kidney stones may occur.
Extreme dosages from supplements may cause vitamin D toxicity. Vitamin D toxicity is unlikely to be caused from food or sun exposure:
- sun exposure can’t result in vitamin D toxicity, as the hot skin limits the formation of D3. On the contrary, tanning may cause vitamin D toxicity. There are cases that often application of artificial UV radiation increased blood levels of vitamin D above 375–500 nmol/L (150–200 ng/mL)!
- cod liver oil is the richest dietary source of vitamin D. It contains 1,360 IU per serving! Other good dietary sources of vitamin D are fish, such as trout and salmon, as well as all fortified products. Vegan foods are poor sources of vitamin D.
What’s the best time to take vitamin D?
You should take vitamin D supplements with a meal. As vitamin D is a fat soluble vitamin, it’s best absorbed when consumed with a meal high in fat. Seeds and nuts contain healthy fats, such as omega-3s.