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Hey Everyone,

I got my first “ask me a question”….woohoo. I was really excited to get it!! It is from Miss Jenny and here is what she asked:

Ok…I want to get started on dosage calculations. I’ve always struggled with unit conversions. Any tips…any idea where to find a printable chart? Is there a quick and easy “trick” to remembering these conversions??

Thanks!

If you are a nursing student or a soon-to-be nursing student you will be required to learn how to do dosage & calculation problems. Dosage and calculation problems are solved in order to figure out how much medication you need to give your patient. You will see these problems on NCLEX-RN & HESI (both mid-curricular & exit). Dosage & Calculation problems are used to solve many things. For example, you use D&C problems to calculate how many ml (milliliters) you need to draw up in a syringe to give in a IV line or how to set your flow rate for an IV pump.

Before you even start doing any dosage & calculation problems you have to memorize the following equivalents. It took me a couple of days to get it memorized. To help you memorize, I suggest writing each equivalent over and over, so when you go and take your test you can simply hurry up and copy the table on your paper from memory so you can refer to it while you are taking your test. I found this has always been helpful for me. Here are the following equivalents that you must engrave in your brain:

Note: mL and cc (said like this: cc’s) are exactly the same thing. I got really confused on this when finally one of my teachers told us mL and cc are the same thing and the whole class was like “oh really”. The reason I got confused was because I would hear a nurse say draw up 8 cc of that and I would be like “what?” it says mL on the syringe….so just to let you know mL and cc are the same thing LOL.

Once you memorize those equivalents you are set. I really haven’t found a trick to remembering them like a mnemonic. I suggest just memorizing them because eventually they start to click. Now to start solving some problems. I am going to work out some problems and explain step-by-step how to do them.

At my college, they have us solve our dosage and calculation problems using a formula called Dimensional Analysis…some colleges follow different ways but I think this is the easiest method. When working Dimensional Analysis there are two very important things to remember:

1. Begin with the unit of measurement you are solving for. This unit of measurement should always be in the numerator (top number) of the first box of the equation.
2. You must be able to cross the units out as you move diagonally from the denominator (bottom number) in one box to the numerator in the next box. This problem is complete when you have crossed out all other units of measurement leaving only the units of measurement you are trying to find out.

With that said here we go:

1. Solve: 5 Tbsp =            oz
2. Remember start out with the unit of measurement you are solving for which is oz in this case. Then think “how many oz are in a Tbsp”? From you memorized equivalents you will know that there are 2 Tbsp in 1 oz. So on paper you will have something that looks like this:

3. 1 oz

   2 Tbsp

4. Now you need to find out how many oz are in 5 Tbsp. Remember the second rule listed above. You have to be able to diagonally cross out the denominator and numerator. So you problem will look like this:

5.  1 oz     X    5 Tbsp =  5 oz  =  2.5 oz

   2 Tbsp           1              2

1. Solve: 3 tsp=           mL
2. Remember start out with the unit of measurement you are solving for which is mL in this case. Then think “how many mL are in a tsp”? From you memorized equivalents you will know that there are 5 mL in 1 tsp. So on paper you will have something that looks like this:

3. 5 mL 

   1 tsp

4.  

    

   Now you need to find out how many mL are in 3 tsp. Remember the second rule listed above. You have to be able to diagonally cross out the denominator and numerator. So you problem will look like this:

5. 5 mL  X    3 tsp =  15 mL

   1 tsp           1            

    

1. Solve: 2 G=       mcg

2. Remember start out with the unit of measurement you are solving for which is mcg in this case. Then think “how many mcg are in a G”? According to the equivalent chart there isn’t a part for how many mcg are in a gram….right?! BUT there is an equivalent for how many mcg are in a mg….correct?! So with this problem you will be adding another step. From you memorized equivalents you will know that there are 1000 mcg in 1 mg. So on paper you will have something that looks like this:

3. 1000 mcg

       1 mg 

4. We are solving for Grams so we must get our problem where it includes grams. So now repeat step two of this problem. Ask yourself “how many mg are in one Gram?” According to our equivalents, there are 1000 mg in a gram. So you problem will look like this:

5. 1000 mcg    X    1000 mg

       1 mg                   1G

6. Now you need to find out how many mcg are in 2 G. Remember the second rule listed above. You have to be able to diagonally cross out the denominator and numerator. So you problem will look like this:

7.  1000 mcg    X    1000 mg   X   2 G=   2,000,000 mcg

       1 mg                   1G                1

Here are some practice problems for you to solve on your own….below includes the answers.

1. 675 mg=           G
2. 150 lb=            Kg
3. 20 mL=             tsp
4. 25mL=              Tbsp
5. 12 tsp=             oz
6. 5 oz=              mL
7. 0.023 G=            mcg
8. 2,550 G=                Kg
9. 5 mg=                    mcg
10. 25 tsp=                  Tbsp

Answers:

1. 0.68 G
2. 68.2 Kg
3. 4 tsp
4. 1.5 Tbsp
5. 2 oz
6. 150 mL
7. 23,000 mcg
8. 2.6 Kg
9. 5,000 mcg
10. 8.5 Tbsp

I remember learning these things and I wasn’t very good at them. I wasn’t use to the method of solving them and also math has NEVER been my thing. I figured that picking nursing as my career I wouldn’t have to worry about any math but I was wrong. I promise that although this may look daunting & confusing at first it will eventually click. You have to practice them over and over until you get it. I practiced this problems over and over until I was blue in the face and FINALLY I got it. Now D&C problems are actually my strength! I suggest buying a book or searching the web for a great site that has dosage and calculations problems to solve.

Here is a great website I found very useful for studying this dosage and calculation problems. I used it a lot because it has practice questions on it. Click Here for the Site If you are just starting on these problems I suggest doing the Metric problems first.

Thanks for the question Jenny ! I hope this helped you and if you ever have any more questions just ask me. Remember “hit me with your best shot”….lol!

Until next time,

Sarah

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