Excessive vitamin D in the body is known as the illness hypervitaminosis D. Vitamin D is manufactured by the human body in direct correlation with sunlight exposure. Only 15 minutes of sunshine is needed daily to produce enough vitamin D for the body, but a full day in the sun will not cause an overdose, according to The Merck Manuals Online Medical Library. However, taking an excessive dose of oral vitamin D may lead to toxicity and severe symptoms.
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Elevated Blood Calcium
Vitamin D is integral in the absorption process and the use of calcium by the body, according to The Merck Manuals. All signs and symptoms of too much vitamin D ultimately stem from a calcium overdose, because the processing of calcium will stop with excessive vitamin D present. High blood calcium levels, known as hypercalcemia, are easily diagnosed with a simple blood test.
Irritability, Fatigue, Bone Pain and Weakness
An erratic release of calcium will impact the central nervous and musculoskeletal systems, generating a host of signs and symptoms. Nervousness, irritability and fatigue are indicative of hypercalcemia from excessive vitamin D. Musculoskeletal complaints include bone pain and muscle weakness, as calcium is used to support bone growth and repair and muscle contractions.
One of the most severe and potentially irreversible signs of vitamin D overdose is kidney damage. After chronically high levels of vitamin D are ingested, frequent urination and development of kidney stones are reported. Untreated stones and kidney damage may lead to irreversible kidney failure.
Nausea and Vomiting
Vitamin D and calcium are initially absorbed for use through the gastrointestinal tract, specifically the colon. Too much vitamin D may cause extreme weight loss and decreased appetite, according to The Merck Manuals. Nausea, vomiting and dehydration with resulting constipation may also occur.