Hypervitaminosis D, also known as vitamin D toxicity, is a rare but potentially serious condition that occurs when you take in too much vitamin D. Excess amounts of vitamin D can cause abnormally high levels of calcium in the blood, which can affect bones, tissues, and other organs. Left untreated, this condition can lead to high blood pressure, bone loss, and kidney damage.
This condition is usually caused by taking high-dose vitamin D supplements, and as such, treatment involves discontinuing or lowering your intake. Your doctor may also recommend that you lower the amount of calcium in your diet. Careful monitoring is necessary until your vitamin D levels are back to normal.
Excessive amounts of vitamin D in the body can cause calcium levels in the blood to rise. This can lead to a condition called hypercalcemia (too much calcium in your blood), which can cause a variety of symptoms, including:
- loss of appetite
- weight loss
- excessive thirst
- excessive urination
- irritability, nervousness
- ringing in the ear (tinnitus)
- muscle weakness
- nausea, vomiting
- confusion, disorientation
- high blood pressure
- heart arrhythmias
Longer-term complications of untreated hypervitaminosis D include:
- kidney stones
- kidney damage
- kidney failure
excess bone loss
It is unlikely that you would take in too much vitamin D from the foods you eat or from exposure to the sun. In most cases, this condition is caused by taking more than the recommended daily value of vitamin D supplements. Failure to read the amount of Vitamin D in your multivitamin and then supplementing your nutritional mineral intake with added calcium and Vitamin D. Commonly prescribed medications such as thiazide diuretics used to treat high blood pressure and digoxin, used to treat heart diseases, can cause an increase in Vitamin D in the blood.
Elevated levels of Vitamin D have also been reported with the use of estrogen therapy, long-term use of antacids and isoniazide, an anti-tuberculosis medication. (umm.edu)
According to the Mayo Clinic, the recommended dietary allowance of vitamin D for most adults is 600 international units a day (IU). Doctors may prescribe higher doses to treat medical conditions such as vitamin D deficiency, diabetes, and cardiovascular disease. However, these prescription doses are only meant to be taken for a short period of time. Daily use of high-dose vitamin D supplements for several months has been shown to be toxic (Mayo Clinic, 2011).
You are at increased risk of vitamin D toxicity if you take vitamin D supplements and have other existing health problems such as:
- kidney disease
- liver disease
See your doctor if you are experiencing symptoms of hypervitaminosis D. To diagnose this condition, your doctor will review your medical history and may ask questions about any prescription and over-the-counter medications and supplements you are taking.
Your doctor may also perform a physical exam and ask questions about your symptoms. While vitamin D toxicity may present a variety of symptoms, those most commonly associated with this condition include high blood pressure, excessive thirst, and polyuria, a condition in which a person passes large volumes of urine. If your doctor suspects toxicity based on these symptoms, they may order several tests to confirm diagnosis, including:
- blood tests to check vitamin D levels, calcium, phosphorus (used to determine if kidney damage is present)
- urine tests to check for excessive amounts of calcium in the urine
- bone X-rays to determine if significant bone loss has occurred
Your doctor will likely advise that you stop taking vitamin D supplements immediately. Your doctor may also recommend certain measures to offset the excessive amount of calcium in your blood, such as lowering the amount of calcium in your diet temporarily. In some cases, corticosteroids or bisphosphonates may be used to suppress the release of calcium from your bones (prevention of bone resorption) (Merck). Your vitamin D levels must be frequently monitored until they return to normal.
Not many foods contain vitamin D naturally. Among those that contain small amounts are:
- fatty fish, like salmon, tuna, and mackerel
- beef liver
- egg yolks
- some mushrooms
Because of the lack of vitamin D in nature, many foods are fortified with vitamin D. Common fortified food items are:
- breakfast cereals
- orange juice
- soy beverages
- infant formula
You also get vitamin D when your skin is exposed to sunlight. You cannot get vitamin D through sunlight that comes through a window.
According to the Office of Dietary Supplements, the amount of vitamin D you require varies with age (ODS). Babies up to 12 months old require 400 IU, people over the age of 70 need 800 IU, and all other adults need about 600 IU per day.