Medication calculations

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Hi does anyone have any tips on how to calculate drug dosages etc... I have my OSCE soon and part of this is to do drug calculations without a calculator. I understand the simple ones for example: the patient is prescribed 10mg of midazolam there are 5mg/5ml of solution so I know I would give 10ml to make the correct dose. What I struggle with is when you are asked a question asking to convert micrograms to mg or mg to g etc...

for example a patient is prescribed 50mg of something but you only have the medication in micrograms how do you convert these without a calculator without making a mistake.

I also struggle with how to work out IV rates.

Maybe I am being silly but this does worry me, I need to know this. I am not very good at maths so I am worried this problem may hold me back in some way.

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Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.

This site should help......DosageHelp.com - Helping Nursing Students Learn Dosage Calculations

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I have found a nice document that would help you understanding the medical calculations and unit conversions.

Maths for Nurses:

Unit conversions

This booklet will provide an overview of the unit conversions for nursing students.

- University of Leeds Maths for nurses

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As far as conversions go, memorize your conversion factors first. (1 kg = 2.2 lbs, etc.)

Then Remember

M_3__King Henry Diet BY Drinking Chocolate Milk__3_M

This stands for

Macro_3__Kilo Hecto Deka Base Unit Deci Centi Mili__3_Micro

The base can be liters, grams, meters, etc.

(Google Metric conversion charts to see more examples of this)

You just move the decimal one time for each unit

Example: you have 4g and want to know how many mg you have.

Your decimal is right behind the 4 and you move it 3 times to the right to make it mg. so you have 4000. I usually draw the UUU underneath the number to show how many places I need to fill in with zeros.

The macro and micro have ___ spaces between them because you have to move 3 spaces between macro and kilo and mili and micro.

Just ask if it doesn't make sense. It would be way better with an actual picture.

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Either learn:

Mega^6, Kilo^3, Deca^1, Deci^-1, Centi^-2, Milli^-3, Micro^-6, Nano^-9

Or I was also taught if you need to convert between those smaller numbers such as from milligram to microgram then just know it's always 1000 micrograms = 1 mg. It goes the same for how many nano grams in a microgram; hence, you notice on the chart I gave you the powers are always increasing 3 fold. Now you should be able to tell me how many milligrams in a centigram without even using a calculator, which I hope your thinking 10. For your example...Your medication is in 50mg but you only have lets say 100mcg on hand.

100mcg x 1mg / 1000 = 0.1mg

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