student

I think you should seek help from an instructor; this is probably best taught in person.

I'll try, though. 0.9mL is 9/10ths of a mL, right? So if you have a one mL syringe, probably there is going to be a line for each 1/10th of a mL. Do you have some syringes in your lab that you can look at and play with a little bit? This might help you familiarize yourself with this.

Think about what the number represents. 2.1 is two and one tenth. A little more than two. 0.1 is 10% of a mL. Or 1/10 of a mL. It takes ten 0.1mLs to make one entire mL. If you look at a one mL syringe--10% of it or one tenth would be 0.1mL. When you are reconstituting something that requires 2.1mL. Instead of thinking about the numbers, think about it in very a concrete fashion. If you had 2.1 dollars, you would have two dollars and ten cents, for example. 2.1 pizzas would be two entire pizzas and 10% of another. So when you are drawing up a med with 2.1 mLs of penicillin, you pick a syringe that is a 3mL syringe, you draw up two entire mLs, and then you draw up a little more. A 3mL syringe is probably going to have lines that represent 0.2mL--that is, every small line mark 0.2. So if you need 2.1 you draw up past the 2 mL mark, to half-way in between the 2mL and the next line marked. Does this make any sense?

This is basic metric system--you can start by reviewing that. If you don't have a drug calculation textbook, I HIGHLY recommend one for you. A lot of these type of questions that seem so complicated in your mind are no brainers once is it laid out for you. This is really quite basic, though. I think you would be best served by getting a drug calc book that has pics of syringes in it, to bring it into a more concrete, visual sense. My book from school had MANY pics of syringes and questions on how to draw something up. It was called "Dimensional Analysis for Meds"

http://www.amazon.com/Dimensional-Analysis-Meds-Anna-Curren/dp/1401878016/ref=pd_bbs_2?ie=UTF8&s=books&qid=1228856893&sr=8-2

I'm sure you can find it used for pretty cheap on sites like http://www.half.com Don't let the long, fancy title of the book scare you. It offers very in depth, step by step instructions for even the most basic of drug calculations, and it includes many pictures and examples. If you are struggling in this area at all, this is a good book to get.

Let me ask you--where are you at in your nursing school? I'm assuming you are still doing prereqs. Or have you started nursing school? Do you have one school in mind? If so, check their library--they should have copies of most of their text books, and one required or recommended textbook is going to be a drug calculation book. You can then check it out for free.