Can someone verify this for me?




148 Posts

Specializes in LTC. Has 6 years experience.

1 g = 1000 mg

0.5 g = 500 mg

available - 250 mg tabs

250 x 2 = 500

answer 2 tabs

netglow, ASN, RN

4,412 Posts

sorry couldn't get this stupid thing to show dimensional analysis. Whatcha do is go back to chemistry and do your calculation exactly as you would for any conversion.


446 Posts

Wow- I cannot believe how wrong I got this! I am going to go back right now. I was always strong at math, but obviously my form is SUFFERING for this class. :eek:


25 Posts

Focus on the dose which the doctor prescribed, 0.5 grams, to be given; so you will need to do a basic proportion to figure out exactly how many pills are to be given.

Your focus is strictly on the exact dose and how much of a pill(s) will account for that dose.

Take what you know (1000 mg is to 1 gram) and then do your pharmacology conversion (to find the equivalent)

1000 mg : 1 gram :: X mg is to 0.5 grams

1000 : 1 :: 500 : 0.5

Read this as follows:

1000 mg is to 1 gram as X (how many?) mg is to 0.5 grams

Cross multiply the proportion, and then divide

1000 : 1 :: 500 : 0.5

1000 x 0.5 = 500

1 x 500 = 500 mg

500 mg/250 mg = 2 pills

The answer is 2 pills.

Good luck with your pharmacology. Just remember the basic proportion for all doses and you will have no problems.

Specializes in Gerontology. Has 37 years experience.

I worked it out a bit differently.

0.5 grams = ? mg.

I know that there are 1000 mg per gram. so therefore 0.5 grams is equal to 500 mg. The pills available are 250 mg, so I would give 2 pills to equal 500 mg dose.

The 500 pills is just extra information that you don't need for this question.

I would advise goggling the metric system. It is actually a very simple system once you understand it.

TheCommuter, BSN, RN

226 Articles; 27,608 Posts

Specializes in Case mgmt., rehab, (CRRN), LTC & psych. Has 17 years experience.

I. Doctor's order: 0.5 grams

a. 0.5 grams = 500mg

b. 250mg : 1 tablet :: 500mg : 2 tablets

c. answer = 2 tablets


240 Posts


A few folks have been kind enough to have given you the correct answer of two tabets to be given and how they calculated it. Now for the bad news. These calculations are going to become more complex, there will be reconstitutions at various concentrations, feeding formulas at various strengths, IV drip rates, etc. I recommend that you either meet with your instructor or better yet, seek help from one of your other instructors. This math is VERY important, you need to understand it well. This may mean that you spend a considerable amount of time on practice problems. Keep in mind that you will be pushing meds into a human soon. I am fortunate that all of my instructors speak english as a first language and most seem to have a caring attitude about us students. Hats off to you for seeking help here. I wish you the best of luck in working towards your education.


Has 19 years experience. - basic tutorial on getting started with pharmacology math. at the bottom of this home page is a drop down box where you link into any of the following subjects: common conversion factors/equivalencies, common abbreviations, ratio and proportion, iv problems, titration problems, and pediatric pharmacology math. -- the start page of this pharmacology math tutorial presented by the nursing department at the san antonio college. by clicking on the "go figure" button you can access quizzes on basic med calculations, iv, pediatric and ob med calculations. the quizzes all have answers. follow the directions.

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