About 35% of U.S. adults are deficient in vitamin D, according to the Cleveland Clinic. This fat-soluble vitamin is essential for helping the body absorb calcium, supporting bone strength, and boosting immune function. You can get vitamin D naturally from sunlight, fatty fish, fortified dairy products, and supplements.

But experts warn that you can, in fact, get too much of a good thing. High doses of vitamin D can trigger dangerous side effects—including nausea, vomiting, kidney stones, and even death, reports Eating Well.

How Toxicity Happens

Vitamin D deficiency often leads people to overcompensate with supplements, sometimes taking far more than their bodies need. Unlike water-soluble vitamins that flush out easily, vitamin D builds up in fat tissue. Over time, this can cause dangerously high blood calcium levels, especially when very large doses are taken for several months.

“Vitamin D acts like a hormone in the body,” experts note, which is why excess intake can disrupt normal function and damage organs.

Warning Signs of Vitamin D Overload

Symptoms of vitamin D toxicity may include:

• Persistent nausea
• Vomiting
• Weakness
• Frequent urination
• Confusion
• Dehydration
• Elevated calcium levels, which can cause kidney stones or organ damage

If left untreated, vitamin D toxicity can progress to kidney failure, irregular heartbeat, and even death. Anyone experiencing these symptoms while taking supplements should seek medical advice immediately.

How Much Is Too Much?

The recommended daily allowance (RDA) for vitamin D varies by age and health status:

• Children, teens, and adults up to age 70: 600 IU daily
• Adults over 70: 800 IU daily

In general, experts say you should not exceed 4,000 IU per day from all sources unless directed by a healthcare professional.

Safer Ways to Get Vitamin D

Whenever possible, aim to meet your vitamin D needs through food and safe sun exposure. A simple blood test can reveal your vitamin D levels, allowing your doctor to provide personalized recommendations.