Accuracy in dosage calculations and solution rates is a highly important aspect of safe nursing care. The following notes and examples provide simple methods of dosage calculations, solution rates and conversion tables that can help provide safe easy methods to ensure drug administration safety for our patients.
Volume (ml) / Time (mins) X Drop Factor = Drip Rate (drops/minute)
Drop factor is usually 10, 15 or 20 (unless indicated otherwise, drop factor should be assumed as 20)
Example 1: Jane has an order for 500mg Clarithromycin every 6 hours. The drug comes in 250mg capsules. How many capsules does Jane require?
1 capsule contains 250mg, so since Jane requires 500mg, the nurse should administer 2 capsules.
Example 2: A digoxin ampule contains 500mcg in 2ml. If a patient is prescribed 350mcg, what volume should he receive?
500mcg = 2ml; 350mcg =?
2ml x 350mcg = 700 / 500 = 1.4ml
Example 3: 625mg are prescribed to a patient. Tablets come in 1.25g each. How many capsules should the nurse administer?
1250mg = 1 capsule; 625mg =?
625mg / 1250mg = 0.5 = half a tablet
Example 4: Heparin contains 5000units per ml. How much Heparin should be administered if a patient requires 6500units?
5000 units = 1ml; 6500 units =?
6500 units / 5000 units = 1.3ml
Example 5: A patient is prescribed IV paracetamol at 15mg per kg. The patient weighs 45kgs. How much paracetamol should be administered by the nurse?
1kg = 15mg; 45kgs =?
45kgs x 15mg = 675mg
Example 6: A patient needs 500ml of 0.9& NaCl. Drip chamber is set to 25ml per hour. How long will the fluid take to be administered to the patient?
25ml = 1hr; 500ml =?
500ml / 25ml = 20 hours
Example 7: 300ml of blood needs to be transfused over 4hrs at 20 drops/ml. What is the drip rate?
volume in ml / time in minutes = 300ml / 240 minutes = 1.25 x 20 (drop factor) = 25 drops per minute
Example 8: A patient is to receive 2lt of 5% Dextrose in the next 15 hours. What is the flow rate?
15hrs = 2000ml; 1hr =?
2000ml / 15hrs = 133ml/hr
Example 9: A patient needs 750ml of 0.9%NaCl to be administered over 9 hours at 10 drops per ml. What is the drip rate?
750ml / 540 minutes = 1.3888 x 10 (drip factor) = 13.88 = 14 drops/min
Example 10: Calculate the required flow rate when administering one litre of fluid over 4 hours.
4 hours = 1000ml; 1hr =?
1000ml / 4hrs = 250ml per hour
Below you can find a collection of videos that can help provide a more visual approach to dosage calculations.
Dosage Calculations
Special thanks to the creator of the featured videos on this post, specifically Youtube Channel RN Kid.
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Claire is keen about public education on health-related subjects as well as holistic patient-centered care. She is also passionate about spreading awareness on the negative effects that domestic abuse leaves on its victims’ mental, emotional, social and physical wellbeing.
Claire aspires to continue studying following completion of her Nursing Degree, because she truly believes in lifelong education.
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