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You'll find everything you want to know about vitamin D right here.
Vitamin D can
Best way to get it? Sunlight! Nature's own prescription.
Next best way? Supplement vitamin D3.
It's better than Health Insurance and costs less than $2 per month!
Alex St Clair
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Vitamin D3 capsules:
Vitamin D3 drops:
To review these products, please see Before you Buy Vitamin D
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Evidence from sunlight.
Evidence from accidental overdose.
Toxicity from vitamin D supplements
Testing for vitamin D toxicity.
Hypersensitivity to vitamin D.
Symptoms of vitamin D toxicity.
Treatment of vitamin D toxicity.
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Vitamin D is toxic in excess, but for most people, such an excess could only be produced by taking huge doses of vitamin D supplements.
It is unknown for sunlight to cause vitamin D toxicity, and we know that just 20 minutes of full body exposure to sunlight can produce the equivalent of at least 10 000 IU of vitamin D3 in fair-skinned people.
Lifeguards, and many other people who spend day after day in full sun, sometimes with little protection, do not suffer from vitamin D excess.
(Sure, we need to be careful about over-exposing our skin to the sun, but the harm we might do to ourselves would not be from too much vitamin D.)
The amount of vitamin D available from natural foods is relatively small, and from fortified foods, somewhat greater, but not enough to prevent deficiency, let alone cause toxicity.
The only toxicity issue related to food arises when a food manufacturer accidentally overdoses the food with vitamin D, while creating a fortified food. (This happens extremely rarely. Nevertheless, it seems to be one of the more common causes of vitamin D toxicity!)
But when people think about vitamin D toxicity, their concern is usually that they might take too many vitamin D supplements.
The amount of supplemental vitamin D3 that would produce toxicity in healthy individuals is not known exactly. It would certainly vary from individual to individual.
Evidence from accidental overdose of vitamin D in individuals and communities has given some indications.
It appears from this evidence that human toxicity starts at around 40,000 IU per day, but only when taken continuously for at least three months.
Some people have taken much larger doses than this, for even longer periods of time, without experiencing toxicity.
But it is now possible to buy vitamin D3 capsules with 50,000 IU per capsule. so taking even one of these mega-doses per day on an ongoing basis could eventually result in vitamin D toxicity in susceptible people.
First, know what dose is appropriate, both to treat vitamin D deficiency and to maintain optimum vitamin D blood levels. See our page Vitamin D Dosage.
The best way to protect yourself from vitamin D toxicity is to monitor your vitamin D status by taking a 25(OH)D blood test. This provides the assurance that your vitamin D level is within the normal range.
A periodic vitamin D blood test (every 6 months or so) also helps to protect you against toxicity that could arise if you were accidentally taking more vitamin D than you thought.
This has occurred in a handful of cases of vitamin D toxicity reported in recent years, where huge doses of vitamin D were mistakenly included in supplements by the manufacturer.
When we take vitamin D supplements, the vitamin D is converted by the liver into calcidiol, also known as 25-hydroxyvitamin D, or 25(OH)D for short.
That's the form of vitamin D which is stored in the body (in fat, muscle and blood) and also the form measured by the blood test.
25(OH)D Blood test results
Vitamin D Status
|High, but not toxic||66-100||164-250|
|Toxicity possible||above 100||above 250|
Extremely high doses of vitamin D would have to be taken over several weeks or months to raise blood levels above 100 ng/ml.
Although toxicity is considered possible above 100 ng/ml, most cases of vitamin D toxicity occur at even higher levels than this, usually above 200 ng/ml.
If a test shows that a person's vitamin D level is in the possibly-toxic range, the doctor will order further tests (including active vitamin D, calcium in urine and calcium blood levels) to determine if vitamin D toxicity is actually present.
There are some conditions which render a person hypersensitive to vitamin D (for example, primary hyperparathyroidism, sarcoidosis, granulomatous diseases, and some cancers).
Such people should be under their doctor's care, and should only take vitamin D if it is prescribed for them.
(But most sick people, including most cancer patients, can benefit greatly by having their vitamin D levels optimized.)
Vitamin D toxicity manifests as too much calcium in the blood, or hypercalcemia. Symptoms of this condition may include:
Not all symptoms may be present in every case, but a person suffering from vitamin D toxicity would not feel at all well.
Some of these symptoms could be mistaken for gastroenteritis, in the absence of laboratory tests. Bear in mind, vitamin D toxicity is extremely rare, so most doctors will never come across a case.
If the condition is not treated, excess calcium may be deposited inside kidneys, heart and other organs, which could be life-threatening.
The treatment of vitamin D toxicity should be under the direction of a knowledgeable physician. Treatment generally comprises:
until serum 25(OH)D level is back into the normal range. This may take several months.
In most cases, appropriate treatment leads to a full recovery.
Also see Before You Buy Vitamin D.