We use MSM for our kids 1000-2000mg twice a day. It is excreted throught your kidneys within 12hrs. I take between 5000-10,000mg per day normally and up to 50,000mg if using therapuetically. It is usually a good idea to start out with mimimal dosages though because it has a detoxifying effect and can cause muscle cramps/intestinal discomfort/muscle and head aches. Other than the detoxifiying effects, there are no known side effects and no toxic levels. It increases the permeability of the cell walls which helps with absorbtion of nutrition as well as the excretion of toxins. It works best when used with Vitamin C (we give our kids 250-500mg. The MSM increases your bodies ability to absorb and utilize the Vitamin C, therefore you can take more. We use muscle response testing to determine how much the body needs and can assimulate. We get our MSM from a farm COOP in powder form. Its much cheaper and is the same thing. I believe the brand we get is called ultrapure and is 99.9%pure. Make sure it is 99.9% pure. I believe we pay about $43 for 4 pounds of it. There is about 5000mg in one teaspoon.