If you take vitamin D supplements, watch the dose to be sure you don’t consume too much. Your body eliminates water-soluble vitamins when you get more than you need, but fat-soluble vitamins accumulate in your system. Since it’s fat-soluble, vitamin D may build to toxic levels. When that happens, it causes bone loss, kidney stones and calcification of your heart or other soft tissues.
Causes of Toxicity
Your skin produces vitamin D from exposure to sunlight, but toxicity from this source has never occurred, according to the Linus Pauling Institute. Foods that are fortified with vitamin D, such as milk, are the primary source for most people because very few foods contain vitamin D naturally. However, you're not likely to consume enough from food to reach toxic levels, notes the Office of Dietary Supplements. The primary cause of vitamin D toxicity, which is called hypervitaminosis D, is taking large doses of supplements on a regular basis.
Effects of High Levels
Vitamin D regulates the amount of calcium absorbed during digestion, as well as how much calcium circulates in your bloodstream. High levels of vitamin D cause an increase in calcium. Symptoms of high calcium, or hypercalcemia, can appear in less than four weeks if you take high doses of vitamin D daily. Early symptoms include fatigue, irritability, vomiting, dehydration and constipation. You may also experience a loss of appetite or muscle weakness. As hypercalcemia gets worse, your heart may beat irregularly. If the condition remains untreated, high levels of calcium can cause kidney stones and calcification of soft tissues, including your blood vessels and heart.
The Food and Nutrition Board of the Institute of Medicine determined the recommended dietary allowance, or RDA, for vitamin D based on the amount you need to maintain strong, healthy bones. Men and women need 600 international units, or 15 micrograms, of vitamin D daily. The precise amount of vitamin D it takes to reach toxic levels is not known, according to “Dietary Reference Intakes for Calcium and Vitamin D.” To ensure your safety, you should never consume more than 4,000 international units, or 100 micrograms, of vitamin D daily.
Interactions and Warnings
Your risk of developing high levels of calcium from hypervitaminosis D increases if you have kidney disease, hyperparathyroidism, sarcoidosis, tuberculosis or lymphoma, according to the Linus Pauling Institute. Vitamin D supplements may make hardening of the arteries worse. The metabolism of many medications is affected by vitamin D, from over-the-counter antacids to prescription medications such as digitalis, Lipitor and water pills. If you have any of these conditions or you take medications, talk to your doctor before adding vitamin D supplements to your daily regimen.