How Much Vitamin D Is Too Much?

I recently had a blood and urine checkup. Most everything was within normal range (doing well), except that I am low on vitamin D, at 24. The doctor recommended supplements, but said to be careful not to overdo. How much is too much? Is one a week OK? 

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ANSWER: There are several ways to replace vitamin D, but the most common are weekly ergocalciferol (vitamin D-2, usually given as 50,000 units for eight weeks) or cholecalciferol (vitamin D-3, taken daily).

I prefer daily vitamin D-3 as a supplement for most people who are found to have low vitamin D levels. Most people remember better to take one daily, and many people think that after a month of taking weekly vitamin D they are cured and do not take the required follow-up supplements.

While it is true that excess vitamin D can be dangerous, it is very uncommon to have excess vitamin D when taking 8,000 units or less daily. (Some people will need more than that, but doses in excess of 8,000 IU should be guided by blood levels. Some people don’t absorb vitamin D well, and they may need amounts that might cause toxicity in other people.) The general recommendation is 1,000 to 2,000 units of vitamin D-3 daily. However, D-2 comes in 5,000 and 10,000 units in addition to the 50,000, so it is fine to use weekly dosing if you prefer.