Now a days, the medicine dropper not only has millimeters but also milligrams. You need to check it out first or you can even ask the doctor for help. The dosage standards have changed in the recent years by the way. If it says only Millimeters, you can substitute it with Milligram. I faced this problem with my kid's medicine and consulted the doctor who told me that its the same thing as Milligram. So the dose should be the same both ways.