Is there such a thing as too much of a good thing? Anyone who has stared down an entire chocolate cake can attest that yes, there is.
Despite levels of 5,000 IU and even 10,000 IU of vitamin D being readily available with the click of a button, The National Academy of Medicine (formerly the Institute of Medicine) recommends no adult should exceed 4,000 IU a day or else they put themselves at risk of serious health complications.
“Many people are taking too much vitamin D.” Dr. Joann Manson of The Brigham and Woman’s Hospital is working on a study of 25,000 participants to check their vitamin D blood levels. 
The American Academy of Dermatology agrees. Dr. Weinstock of Brown University commented at the annual meeting that “there is an increased risk of falls and fractures associated with vitamin D ‘mega dosing’.”
What is considered too high or too low?
“You shouldn’t bypass the satiety level. Your stomach is only so big for a reason.” said Dr. Paul Offit, an infectious disease specialist.
Dr. Offit offers a good rule of thumb: there are 1,000 milligrams of vitamin C in one tablet. That’s the equivalent of eight cantaloupes. Would you eat eight cantaloupes a day? If you answered no, then you shouldn’t take that high a dose. “It goes against what nature intends.”
At the end of the day we all want to be the healthiest we can possibly be. Supplements and vitamins can be a great tool to get there, we just need to be mindful of how much is too much. Consider the recommendations, understand how much is too much to self-prescribe, and consult your doctor if you think you need more.