setting up dosage calculation problems

[Tiffunique]

Hello everyone I'm a beginning nursing student and I am having a difficult time setting up the basic dosage problems to solve them. I know how to do the arithmetic to achieve the answer (multiplication or division) I just can't seem to set up the problem correctly to solve it. I think my problem is the basic conversion from one unit to the next. I have memorized all the units but still have trouble converting; knowing larger to smaller units you multiply and smaller to larger you divide. I think I am having a problem with determining which unit is the smaller or largest when converting (example 0.3 mg_______mcg another example 1T____mL.

Thanks for listening!!!!

[Daytonite, BSN, RN]

you are always going to do these problems more efficiently if you learn how to set them up and work them using dimensional analysis which requires multiplying fractions together and canceling out labels that are unwanted and repeated in numerators and denominators. you can see lots of examples of problems that are worked out by dimensional analysis on this sticky thread:

• https://allnurses.com/forums/f205/dosage-calculations-88867.html - dosage calculations (in the enursing student assistance forum)
  

0.3 mg = 300 mcg

the conversion factor you want to use is

1mg = 1000 mcg

and you set the problem up to factor out the label,

mg

, so you are left with the label,

mcg

, like this. keep in mind that every fraction is also a ratio. whether you put a term in it's denominator or numerator for this kind of problem doesn't matter. what is important is that you keep the two terms together in the same ratio (fraction). dimensional analysis is a way to manipulate the labels. the math is all that is left to do.

0.3 mg/1

(given information)

x 1000 mcg/1 mg

(conversion factor) =

300 mcg

1 tablespoon = 15 ml

the conversion factor you want to use is

1 tablespoon = 15 ml

.

1 tablespoon

(given information)

x 15 ml/1 tablespoon

(conversion factor)

=

15 ml