Taking too much of any type of vitamin D, including D-3, elevates calcium levels in your body, leading to hypercalcemia. While hypercalcemia isn’t common in healthy people, if you take a high-dosage supplement for an extended period of time, your vitamin D levels become dangerously elevated. You’ll likely experience several side effects when this occurs.
Digestive and Urination Problems
As your vitamin D level rises, you may experience digestive or urinary complications. For example, you might urinate more than you usually do, even though you’re not drinking any extra fluid. Then when you try to pass stool, you could find it difficult or be unable to go for days -- signs of constipation. However, in some cases, high vitamin D levels leave you with diarrhea instead. Belly cramps, nausea and vomiting are sometimes associated with these digestive issues.
Weakness and Pain
When your system absorbs excessive calcium after you regularly take too much vitamin D, tissues throughout your body stiffen up. You might notice that your muscles feel weak or you could find it difficult to go about your normal everyday activities. Muscle and bone pain can also occur throughout your body.
Organ tissues and functions could also become affected by consuming high doses of vitamin D over a long period of time. It’s possible to develop calcium-based kidney stones once your vitamin D level becomes too concentrated. In addition your organs, particularly your heart and kidneys, may harden and have a difficult time doing their jobs. Ultimately this can be fatal in extreme cases.
Too much vitamin D can produce some general symptoms as well, such as extreme fatigue and sleepiness. You may notice frequent headaches, experience round-the-clock thirst or have a chronic dry mouth when vitamin D levels surge. Sometimes excessive vitamin D could leave you with a foul metallic taste in your mouth, cluing you in that something is wrong.
Your body makes vitamin D-3 when you go outside and get some sun exposure. But no matter how much time you spend outdoors, your vitamin D levels won’t become dangerously elevated. Your system just doesn’t convert the vitamin D into its active form in this case. Consuming high levels of any form of vitamin D, from both food and supplements, can raise your vitamin D levels, though. To be safe, avoid ingesting more than 4,000 international units daily, although usually side effects don’t start until after you regularly consume more than 10,000 IU daily. This is far above the daily recommendation of 600 IU a day for men and women, according to the Food and Nutrition Board of the Institute of Medicine.