When vitamin D turns deadly: How excess can damage your heart and kidneys
Vitamin D is often praised for its role in bone strength and overall health, but overdoing it can be dangerous. In 2024, a coroner in the UK linked the death of an 89-year-old man to excessive vitamin D intake, ruling that it caused both heart and kidney failure. As the coroner warned, “Vitamin supplements can have potentially very serious risks and side effects when taken in excess.” This case is a stark reminder that when it comes to vitamins, more is not always better.
Health experts, including the Institute of Medicine (now NASEM), recommend 600 IU (15 µg) of vitamin D daily for adults aged 19–70 and 800 IU for those over 70. The Tolerable Upper Intake Level for adults is set at 4,000 IU per day. Exceeding this regularly can raise the risk of toxicity, with chronic doses above 10,000 IU a day being strongly associated with harm. According to the Cleveland Clinic, some people may even develop symptoms at just 2,000 IU a day. Blood levels above 50 ng/mL can be risky, and anything over 150 ng/mL is considered toxic.
Vitamin D toxicity, or hypervitaminosis D, is caused by high blood calcium (hypercalcaemia). Early symptoms can include nausea, vomiting, constipation, abdominal pain and loss of appetite. Neurological effects such as confusion, headaches and weakness may also occur. In severe cases, patients can slip into stupor or coma. As reported by medical reviews, kidney issues such as excessive thirst, frequent urination and kidney stones are common, along with bone pain, muscle weakness and irregular heart rhythms.
The kidneys are often the first organs to suffer. The National Institutes of Health (NIH) notes that excess calcium from high vitamin D can lead to kidney stones, calcium deposits in kidney tissue (nephrocalcinosis), and even acute kidney injury. The heart is not spared either, high calcium can disrupt electrical signals, leading to palpitations, arrhythmias and, in extreme cases, sudden cardiac arrest. Over time, calcium may also harden arteries and heart valves, raising the risk of high blood pressure and heart disease.
While vitamin D remains essential for health, it is best to stick to recommended intakes and consult a doctor before taking high-dose supplements. Regular blood tests can help ensure safe levels, especially for those at risk of deficiency. As this UK case tragically showed, ignoring dosage guidelines can have fatal consequences. In the words of the NIH, “Extremely high levels of vitamin D can cause kidney failure, irregular heartbeat and even death.”