Is it safe to take 2000 to 3000 mg of vitamin d a day?

NO! 10,000 iu safe!: Most adults need to take 5000-8000 iu of vit d per day to achieve optimal blood levels of 50-80. One should not exceed 10, 000 iu/day without monitoring blood levels, 2000 mg equals 80 million units, a highly toxic dose, but I am guessing you are asking about iu, not mg, a common mistake. It is generally not sold in mg quantities.