Medical: What is 250mg on a 3ml syringe?
It does not work that way. MG is weight, ML is volume. It depends on the concentration of the drug. If the drug is 1000 MG per ML then you would need 0.25 ML.
No can do. Ml is a measure of volume and mg is a measure of weight. It's like asking, How big is a pound? A pound of feathers is lots bigger than a pound of gold.