You might think that it’s easy to overdose on Vitamin D since it is a fat soluble vitamin, but this is not true. You would have to take massive amounts of this vitamin for a long time in order to reach a toxic level. Toxicity has been reported after taking 50.000IU per day for several months in a row, which is truly a massive dose.
But enough with that, lets cover the primary Vitamin D overdose symptoms (otherwise known as hypervitaminosis d):
This is a serious condition, and needs to be addressed by a health professional. This only happens when you take too many Vitamin D supplements, it is impossible to reach toxic levels through diet or sunlight alone. The diet just contains too little, you would have to eat massive amounts of cod fish liver oil to reach these kinds of levels and would probably just get sick from all the oil.
When your skin produces Vitamin D, it has a negative feedback system that prevents it from making too much. It might make about 10.000-20.000IU, and then no more. What this means, is that when a certain amount of Vitamin D has been made in your skin, the enzymes in the skin can’t make any more because there’s too much Vitamin D “in the way”. Negative feedback is a very common control method in your body’s physiology.
So the only way for you to get a Vitamin D overdose, is to overdose on a Vitamin D supplement. If you have done that, or suspect that some else has, then these are the primary symptoms of Vitamin D overdose: confusion, weakness, heart arrhythmia, low appetite, constipation, nausea and vomiting.
There is another medical term called Vitamin D hypersensitivity, which is sometimes confused with Vitamin D toxicity, but in reality they are not the same thing. Vitamin D hypersensitivity is usually caused by another condition called hyperparathyroidism. People with these disorders should be under the care of a physician.
The first thing to do in case of a Vitamin D overdose is, obviously, to immediately stop taking all Vitamin D supplements. Then go see your doctor as soon as possible, if your symptoms are severe then you should go to the emergency room.
So, these are the main Vitamin D overdose symptoms. I would recommend supplementing with Vitamin D if you don’t get a lot of sun year round and if you don’t take any massive doses than you should be completely safe. If you are concerned then do it with your doctor’s consent and have him do regular blood tests to check your levels.