I take 12k iu vitamin D a day and I live in a sunny place. Vitamin D poisoning is definitely a thing, but its pretty hard to accomplish and much less likely than one's vitamin D being critically low. As long as you get blood tests with decent regularity (which come back in the normal range) and feel fine, you probably don't have excess vitamin D in your system. Believe me, if you have vitamin D poisoning you will know. The physical symptoms are extremely severe.