5 Serious Side Effects of Taking Too Much Vitamin D

The Safe Upper Limit

The National Institutes of Health (NIH) has set a tolerable upper intake level (the highest daily dose unlikely to cause adverse effects) for vitamin D at 4,000 IU (100 micrograms) per day.4

Research shows that vitamin D toxicity can occur with prolonged daily intake above 10,000 IU, though the exact threshold can vary between individuals.5

Prevention and Safety

Vitamin D toxicity is preventable and starts with smart supplement habits. Here’s how to stay safe:

• Know your vitamin D level: The only way to know if your vitamin D levels are high or low is to have your blood levels checked. “If you are taking a high dose of vitamin D, regular blood tests are a simple way to monitor your levels,” said Barlow. Recommendations for optimal blood levels of vitamin D vary, but usually fall between 40–70 ng/mL.1

• Stick to the safe upper limit: Although people with low vitamin D levels sometimes need higher doses, most healthy adults should keep supplemental vitamin D to 4,000 IU daily unless directed otherwise by a healthcare provider.4
• Check your labels: Patel recommended being careful when taking multiple supplements and noting how much vitamin D is in each. “It’s important that patients know what dosage of vitamin D they are getting from their multivitamin(s) or supplement(s),” he said.
• Work with a professional: If you need supplemental vitamin D, it’s best to work with a qualified healthcare provider and follow their recommendations for safe and appropriate dosing.