Micrograms are more precise than milligrams.
It is being used in most countries throughout the world to measure weight and mass.
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I remember seeing something like this but ugh I don't have my notes on it.
Can you take too much B12? Along with good nutrition and enough exercise, supplements and vitamins like Omega Oils, B Complex, and folic acid will help your body maximize your weight loss efforts.
Some of these units are still in use even though metric system was formally established in 1923.