How Much Vitamin D is Too Much: What Is Safe?

In the vitamin and mineral world, taking too much of something can be potentially dangerous.

Unlike the water-soluble vitamins that are excreted in urine if your body doesn’t need them, the fat-soluble guys tend to stick around a lot longer (they are stored in adipose tissue), so loading up on them can be an issue.

It’s almost impossible to overdose on vitamin D from its natural source, the sun, but when it comes to supplementation, how much is too much? Find out below!

Vitamin D Toxicity—Is It A Thing?

Because of the growing knowledge that vitamin D deficiency can be detrimental to health, the popularity of supplements has skyrocketed.

And with the growing recommendations for therapeutic doses of vitamin D, people could be taking in too much if not medically supervised. As a result, something called exogenous hypervitaminosis D develops ¹.

It’s not common, but because vitamin D is a fat-soluble vitamin, it’s stored in the body, and levels can accumulate to a dangerous degree.

Hypervitaminosis D is characterized by severe hypercalcemia (high calcium) that can persist and lead to serious health consequences.

However, it usually developed from mega-doses of vitamin D rather than spending large amounts of time in the sun.

Under normal circumstances, vitamin D is usually bound to a carrier protein or a vitamin D receptor ^{2, 3}; there is actually very little “free” vitamin D just floating around.

But when intake is excessive, all the VDRs and carrier proteins are tied up, which means free vitamin D levels rise and affect signaling processes.

The process most affected by this is calcium absorption, hence why high calcium levels is one of the primary symptoms of hypervitaminosis D ^{4, 5}.

Optimal vs. Excessive Blood Levels Of Vitamin D

Nearly every cell in your body has a receptor for vitamin D, which makes it essential for proper organ system function ⁶.

But because high levels of vitamin D are found in cold-water oily fish (salmon, sardines, herring, mackerel), organ meats, and dairy, people who follow a plant-based diet may be at risk for deficiency.

For these people, supplementation is a major way of maintaining adequate serum concentrations.

Guidelines for serum levels of vitamin D are as follows ^7-10:

• Adequate intake: 20–30 ng/ml (50–75 nmol/L)
• Safe upper limit: 60 ng/ml (150 nmol/L)
• Toxicity: Exceeding 150 ng/mL (375 nmol/L)

For most people, 1,000-4,000IU of vitamin D daily is enough to support normal serum concentrations.

If you’re getting it from sunshine during warmer months, 30 minutes of mid-day sun exposure provides the same amount of vitamin D as supplementing about 10,000-20,000IU ¹¹.

How Much Is Too Much?

There’s no doubt that the optimal amount of vitamin D is substantially higher than the recommended daily intake, but there is such a thing as overdoing it.

When it comes to how much vitamin D is enough, there’s little known about how vitamin D toxicity happens, making it hard to determine how much is too much.

Most studies suggest an upper limit of 4,000IU to maintain healthy vitamin D levels via exogenous supplementation to remain in a safe range ¹², but anywhere beyond 40,000IU can be highly toxic to humans ^{13, 14}.

Symptoms Of Vitamin D Toxicity

The main symptom and consequence of excessive vitamin D is hypercalcemia—excessive blood calcium levels, which can cause gastrointestinal symptoms like nausea, vomiting, diarrhea or constipation, and weakness ¹⁵.

Vitamin D toxicity is generally reversible within several months, but if prolonged can cause damage to the kidneys and calcification of arteries due to high calcium levels. The typical protocol for resolving vitamin D toxicity is avoiding sun exposure, foods high in vitamin D, and exogenous supplementation.

Final Thoughts

Vitamin D is a required vitamin for normal body function, but like every other supplement out there, there is such a thing as too much.

If you’re trying to ensure your vitamin D levels are sufficient, always opt for sun exposure over excessive supplementation to avoid complications.

And if you want to bump up levels with a vitamin D supplement, ensure you’re sticking to the recommended dose.