Vitamin D toxicity: How excess Vitamin D can harm your kidneys and heart

Vitamin D is widely touted for bone and overall health, but taking too much can backfire. In fact, recent reports have linked extreme vitamin D supplementation to serious organ damage.


In 2024, a UK man died due to complications related to excess vitamin D and calcium. The coroner ruled that an 89-year-old man’s heart failure and kidney failure were caused by excessive vitamin D intake. As the coroner warned, “Vitamin supplements can have potentially very serious risks and side effects when taken in excess.”.





Cases like these underscore that “more” is not always better, and chronic overuse of vitamin D can trigger hypercalcemia (high blood calcium), which harms both the kidneys and the heart.

Recommended intakes vs. overdose

Health authorities generally recommend 600–800 IU (15–20 µg) of vitamin D daily for most adults. The Institute of Medicine (now NASEM) agrees: it sets the RDA at 600 IU for ages 19–70 and 800 IU for older adults.


Anything above these levels should be monitored. In fact, the Tolerable Upper Intake Level for adults is 4,000 IU/day. Staying under this limit is generally safe; beyond it, the risk of toxicity rises. As one review notes, chronic doses above 250 µg (10,000 IU) are classically associated with toxicity.


When it comes to blood tests, most experts agree that 25-hydroxyvitamin D levels above 50 ng/mL (125 nmol/L) can be risky, and levels over 150 ng/mL (375 nmol/L) are usually toxic. Some people are more sensitive, the Cleveland Clinic says symptoms of high calcium can appear in certain individuals taking as little as 2,000 IU per day.

Symptoms of vitamin D toxicity

Vitamin D toxicity (hypervitaminosis D) manifests through the effects of hypercalcemia. Early signs can be subtle, but generally include:

• Gastrointestinal: nausea, vomiting, constipation, poor appetite, abdominal pain.
• Neurologic: confusion, lethargy, weakness, headaches or even stupor/coma in severe cases.
• Renal: excessive thirst, increased urination (polyuria), dehydration; kidney stones or nephrocalcinosis (calcium deposits in the kidney) may develop.
• Musculoskeletal: bone pain, muscle weakness and fractures (from calcium leaching).
• Cardiac: abnormal heart rhythms (arrhythmias), high blood pressure and palpitations.

Effects on the kidneys

The kidneys bear the brunt of hypercalcemia. Excess vitamin D causes calcium to accumulate in the blood, forcing the kidneys to filter and excrete the surplus. Over time, high urinary calcium leads to kidney stones and nephrocalcinosis (calcium deposits in kidney tissue). These deposits can impair kidney function. Patients with vitamin D toxicity often present with acute kidney injury (AKI).

Effects on the heart and vascular system

The heart and blood vessels are also vulnerable. High blood calcium directly affects cardiac cells and electrical conduction. Symptoms include palpitations and irregular heartbeat, and in extreme cases, sudden cardiac events.

Chronic excess vitamin D also promotes vascular calcification. When calcium levels are persistently high, calcium phosphate can deposit in arterial walls and heart valves, increasing cardiovascular risk.


Over time, this may contribute to hypertension or coronary artery disease. The National Institutes of Health (NIH) also: “Extremely high levels of vitamin D can cause kidney failure, irregular heartbeat and even death.”.