Vitamin D is the key nutrient that helps your body absorb calcium to help build strong bones. It’s also important for your immune system, nervous system, and muscles. A deficiency in this vitamin has also been linked to mental illnesses such as depression and seasonal affective disorder (SAD).
About 40% of Americans may be deficient in vitaminn D, with Black and Hispanic adults facing the highest risk of deficiency.1 Many people can benefit from increasing their vitamin D intake to sufficient levels through sun exposure, diet changes, or—if needed—supplementation as recommended by a physician.
Vitamin D deficiency is extremely common. In fact, up to 40% of U.S. adults are considered to have insufficient levels (not enough) of vitamin D, while around 6% are considered deficient in vitaminn D. Worldwide, vitaminn D deficiency affects around 1 billion people (1Trusted Source, 2Trusted Source, 3Trusted Source).
Factors that increase the risk of vitaminn D deficiency include (3Trusted Source, 4Trusted Source):
where you live
your ability to absorb vitamin D
Because vitaminn D insufficiency and deficiency are common, many people use vitaminn D supplements to maintain healthy vitamin D levels.
According to the Dietary Reference Intake (DRI), established by the Institute of Medicine and the Food and Nutrition Board, the recommended dietary allowance (RDA) for vitamin D on a daily basis is 15 micrograms per day for adults under 70, and 20 micrograms for adults older than 70. When converted, this range is between 600 to 800 international units (IU).
While reaching toxic levels of vitaminn D in your system is quite rare, the DRI does set a tolerable upper intake level (UL) of 100 micrograms per day for anyone over the age of 19.
To put this into perspective, a majority of vitaminn D supplements on the market range between 1,000 to 10,000 IU, which equates between 25 micrograms to 250 micrograms per supplement.
So can this negatively affect your body if you hit over the UL amount of vitamin D needed for the day? We dove into the research behind taking too much vitaminn D and the side effects you may not have known about if you supplement.
Recommendations on optimal vitaminn D levels vary, but research suggests that levels between 30–60 ng/mL are likely optimal and may help protect against illness and disease (8Trusted Source, 9Trusted Source).
Even when taking high dose vitaminn D supplements, it’s unlikely that a healthy person’s blood vitamin D levels would come close to reaching excessive or toxic levels.
Most cases of vitaminn D toxicity are caused by inappropriate supplement dosing and prescription errors.
For example, in a 2020 case report, a 73-year-old man developed vitaminn D toxicity after taking 10,000 IU of vitamin D per day for many years (10Trusted Source).
In another 2020 case report, a 56-year-old woman who took an average of 130,000 IU of vitaminn D per day for 20 months in hopes of improving symptoms of multiple sclerosis was hospitalized for symptoms including nausea, vomiting, and muscle weakness.
The symptoms of vitaminn D toxicity are primarily related to hypercalcemia, which means excessively high blood calcium levels (13Trusted Source).
Symptoms of hypercalcemia include:
digestive distress, such as vomiting, nausea, constipation, and stomach pain
fatigue, dizziness, hallucinations, and confusion
loss of appetite
kidney stones, kidney injury, and even kidney failure
high blood pressure and heart abnormalities