Do you still have to do dosages math by hand as an RN now?

litbitblack, ASN, RN · Feb 28, 2016

Yes its important to learn it just so you know it in case you ever need it....Depending on where you work you may not have access to a computer or a calculator and may need to double check a dose. I would know the formulas that your going to use most often depending on where your going to work. I don't remember the IV tubing dose calc. or the pedi one off the top of my head because I never do it but I do know the basic formula I was taught in LVN school. RN school taught dimensional analysis and I just couldn't figure that out but I remembered the first I ever learned.....Dose ordered/dose on hand x medium - for example you have an order for Haldol 2mg supplied in 5mg /1 ml vial. the dose calc would be 2mg/5mg x 1 which would be 0.4 ml

Everline · Feb 28, 2016

It does come up from time to time, but rarely.

Julius Seizure · Feb 28, 2016

I do them every day in pediatrics. If it's complex I use a calculator to double check, but basic numbers I run in my head - like 2mg/kg and a weight of 5kg.

_Skittles_ · Feb 28, 2016

If you're doing chemotherapy you have to be able to do bsa and dosage calculations.

Julius Seizure · Feb 28, 2016

I do them every day in pediatrics. If it's complex I use a calculator to double check, but basic numbers I run in my head - like 2mg/kg and a weight of 5kg.

Should have added....when its complex, I still need to understand the math enough to know if the answer makes sense. Like what if I fat-finger the calculator and hit the decimal point, or an extra zero or something and then my answer is way off....I need to know to say "wait that doesnt sound correct, let me calculate it again."

Natasha, RN, BSN · Feb 28, 2016

Yep, I still do some dosages by hand, and depending on what I am calculating, another nurse will double check.

sallyrnrrt, ADN, RN · Feb 28, 2016

It has been 43.5 years

i can calculate any doseage,

needed in any setting...

once you you got it, you have it...

as pp said it is just algebra

Karou · Feb 28, 2016

IV Heparin is probably the most complex math I have to do. Bolus or initiate a drip based off weight. Drawing up the bolus itself causes a pause, especially if it's less than 5,000 units. Then the initial drip rate. I always grab someone I trust to double check it with me. I'll call pharmacy also to verify my calculations.

Anytime you are giving something that's dosed based off weight, you have to do math. I imagine that pediatric and ICU areas do this more often.

More simple math is drawing up a partial dose vial, or giving only 1/2 or 1/4 a tablet. Partial liquid doses also.

BittyBabyGrower, MSN, RN · Feb 28, 2016

We use calculators but occasionally do head math :) We have every drug calculated and double checked. The worst are IVIG, insulin and heparin...ugh!

awsumsaus · Feb 28, 2016

Can any of you tell me the main formulas for dosages?

I was taught how to do Dimensional Analysis in my pre-req Chemistry class and haven't missed a dosage calc quiz yet (we have to get 100% on our quizzes each semester). If you search "Dimensional Analysis for Beginning Nursing Dosage Calculations" on YouTube there's a chick who explains this method pretty well.

NurseStorm, BSN, RN · Feb 28, 2016

Yes everyday. I do use a calculator but I mostly always write out my equation first unless it is an extremely obvious one that I know in my head. (such as 1000mg of Tylenol, 500mg tabs available=give 2 tabs). When mixing up my IV medications we calculate based on the reconstitution amount. For example, Add 5 ml sterile water to reconstitute powder. Each 1ml contains 250mg of generic med, the order is for 450mg of med. So you write out mL= 1ml/250mg x 450mg= 1.8mL. Then using our manual I may have to calculate how much IV fluid to mix that in, or it may be written out explicitly (ie. mix doses of 1-250mg in 10ml NaCl, mix doses of 251-500mg in 20ml NaCl, ETC). With peds we use liquid meds also that require calculation. eg. 15ml/ml Ranitidine, the dose prescribed is 21mg. How many ml will you give?

or with liquid antibiotics, etc. Also weight based dose checks (1mg/kg recommended amount, child weighs 20kg, dose is 20mg, so therefore is a safe dose). These are just some examples off the top of my head, but yes, we do calculations mostly every day or multiple times a day. If I happen to be working mother baby care that day, it would be less frequent.

Here.I.Stand, BSN, RN · Feb 29, 2016

You always want to know how to do it; I once caught a pharmacy error. It was 20 ml of tegretol; based on the ordered dose and the concentration, pt should have gotten 10 ml, not 20.

I have a fair amount if pts on MgSO4 gtts (TBIs on therapeutic normo- or hypothermia). The MD will order a serum Mg++ goal such as 4-5 or 3-4, and depending on what the result comes back as, we'll increase/decrease bu 25%, 50% etc.

I also give 23% NaCl as a slow push over 10-15 min. That is given for ICPs >20 (intracranial pressure; high ICPs are an emergency, if you haven't learned about that yet). Since it is an emergency, I don't prefer to wait for the equipment room to bring me a syringe pump. Anyway, I need to figure out how many ml/min to push to give the whole vial over 10-15 min.

For MgSO4 I always use a calculator; for 23% I calculate in my head.

Oh, also a couple weeks I had to give KCentra to reverse an elevated INR in a hemorrhagic stoke pt. That drug comes from the blood bank with no pharmacy label -- just to give 1500 units over 15 min. I had two syringes with a total of 2000some units. So I had to figure out how much volume the pt needed.

I don't use formulas like in geometry or physics class...like a couple PPs said it's basic algebra. You have givens and variables, and you have to solve for the variables.