Nclex Math Calculations??

About PennyNickelDime_RN
Joined: Jun '03; Posts: 277; Likes: 45
RN  Emergency Department
Specialty: Oncology, Emergency Department 
Jun 10, '08I took the NCLEX 5/30/08 and had 68 drug calcs, all requiring some conversions. Know your metric conversions ie: mcg/mg/g/kg, lbs to kgs, and oz's to mls and you should be fine. The 1 thing that sort of freaked me out a bit was having to enter my answers in whole numbers. I hadn't seen this in any study prep. By about my 5th question, I was thinking I had screwed up (instead of entering 12.7 I would enter 13 as my answer based on needing to enter a whole number). I finally got a lengthy ped's drug calc that asked the answer be entered using a decimal. Whew! My last question took at least 7 steps and I had to pay close attention to what it was asking, something like figuring out the total dosage to be given in 24 hours and figuring out the dose to be given each time since it had been ordered TID. Once I settled down, I realized the questions had been getting progressively more difficult which I guess is good.
My advise is to use the system that works best for you. I was taught by a teacher who wrote a book about drug calcs using the "backwards method." Once I learned that, I was fairly comfortable with any question. Good Luck! I'm betting you do well.
Voodoo, RN 
Jun 10, '08Thank you for answering my post. What is the "backwards" method? I am absolutely terrible at med calcs and it is stressing me out bigtime. Haven't really had to do them in over a year and totally forgot how.

Jun 10, '08I'll try not to confuse things. Start on the right side of the = sign with the wanted quantity/desired quantity. For instance, we need to know how many mls to give. So, = ? mls. Now start to work the problem backwards. To the left of the = we need something in the problem that has mls in it, like 5 mls of some drug contains 100 mgs of the drug. Be sure that you keep mls in the numerator spot as you'll see shortly. Let's say the order was for 80 mgs to be given once/day and you're figuring our how many mls. To the left of the = we now have 5ml/100mg. The order was 80 mg which you now put to the left of the 5ml/100mg. The mgs cancel out and now you have a basic math/algebra question. 80*5/100=4mls to be given. This method really helps with the longer questions and with drip factors. Email if you want more info or I could give you the address to order/search for the book. Trust me, I'm no math wiz. But this system works.

Jun 10, '08I had 3 very easy math questions 2) mg/kg/dose ...and one ridiculously easy tabs to dose. the order was for 300mg and the pills came in 150mg . I kept double checking thinking this cant be that easy, there has to be a trick.

Jun 11, '08I had one with how my mL/hr for units of insulin and the order was in milliunits. I was so confused at first. lol Math is a strong point for me though. I had 5 math questions. One was actually just converting oz to mls for calculating an intake. The rest were finding the mL/hr when the order was mcg/kg/min.

Jun 11, '08First memorize your math formulas.
And if you have SAUNDERS: Just practice the math claculation that is in that book. That should be good enough.
And while practicing, pay very close attention to the QUESTION asked. The UNITS that the question is asking you in.
After you know amount for what the question is asking you, and in what UNITS, scan to see, if all the units given in your question are in SAME units. All the units should be same.
If it is hour, all your calculated units should be in HOUR. If it is in Minutse, all the calcualted units should be in minutes. If it is mcg, all calculated units should be in mcg etc. Make sure all ur units match.
Pay very close attention to your units even on exam day. Coz, that's where most of us make our mistakes. And then practice as many math questions from your SAUNDERS (if you don't have it, go to your closest library or bookstore) practice there, WRITE down ALL the formulas given there and know it. You'll do fine.
Good luck. You can do this. 
Jun 11, '08I did the Saundes chapter before my first attempt and got 100% on the practice test. However the medication calculation questions I had were slightly different and they threw me off.
Can someone please go over mcg/kg/hr with me as I don't seem to fully grasp that one. I thought I was ok with them but my first test had like 45 of them. 
Jun 11, '08I had 2. relatively easy. except I had never heard the term milliunit before then... yea I guess it was 1unit = 1000milliunits went home and looked it up. Glad I guessed right.