Too much vitamin D can cause abnormally high levels of calcium in the blood. This can affect bones, tissues, and other organs. It can lead to high blood pressure, bone loss, and kidney damage if not treated.
You probably aren't getting too much vitamin D from the foods you eat or from exposure to the sun. However, there have been cases reported due to tanning bed use. And there has been an increase in overall hypervitaminosis D cases in the past few years.
It is usually due to taking more than the recommended daily value of vitamin D. If you take a multivitamin, look at the amount of vitamin D in it. You may not need to take additional calcium and vitamin D if you're getting enough vitamin D from your multivitamin.
Some prescription medications used to treat high blood pressure (thiazide diuretics) and heart diseases (digoxin) can cause an increase in vitamin D in the blood.
Estrogen therapy, taking antacids for a long time, and isoniazide, an antituberculosis medication, can also cause elevated levels of vitamin D.
The Mayo Clinic states that 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, for a short period of time. Daily use of high-dose vitamin D supplements for several months is toxic.
You are more likely to develop hypervitaminosis D if you take vitamin D supplements and have other existing health problems, such as:
- kidney disease
- liver disease
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). Symptoms include:
- 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
Long-term complications of untreated hypervitaminosis D include:
- kidney stones
- kidney damage
- kidney failure
- excess bone loss
- calcification (hardening) or arteries and soft tissues
In addition, increased blood calcium can cause abnormal heart rhythms.
Your doctor will review your medical history and may ask about any prescription and over-the-counter medications and supplements you're taking.
Your doctor may also perform a physical exam and ask questions about your symptoms. If your doctor suspects that you may have hypervitaminosis D, they may order tests, including:
- blood tests to check vitamin D levels, calcium, and phosphorus (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 there's significant bone loss
Your doctor will likely advise you to stop taking vitamin D supplements immediately. They may also recommend that you reduce the amount of calcium in your diet temporarily. In some cases, corticosteroids or bisphosphonates may suppress the release of calcium from your bones.
Your doctor will monitor your vitamin D levels frequently until they return to normal.
Discontinuing or lowering your intake of high-dose vitamin D supplements can prevent hypervitaminosis D. The tolerable upper limit, or the maximum daily intake of vitamin D that is unlikely to result in any health risks, has been set at 4,000 IUs per day. Adverse effects have been seen in those taking less than 10,000 IUs per day over an extended period of time.
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.
To ingest vitamin D naturally, you can eat foods that are rich in it, including:
- cod liver oil
- fatty fish, such as salmon and tuna
- beef liver
- egg yolks
- some mushrooms
You can also find foods fortified with vitamin D, including milk, orange juice, and yogurt. Moderate exposure to sunlight is another source of natural vitamin D. Fifteen minutes or less with your extremities exposed in direct sunlight, before putting on sunscreen, is a great way to improve your vitamin D level naturally.