Percentage concentration (March 2026 NMC update)
1. Percentage concentration
With NMC recent CBT exam update (March 2026) percentage concentration question might be asked in your NMC CBT exam.
Let us have a look how the percentage % (w/v) calculation works.
Drug concentration may also be measured as percentage % (w/v). Percentage means the number of grams of drug dissolved in 100ml solution, i.e. g per 100ml. This is irrespective of the size of the vial or bottle of fluid: e.g. Dextrose 5% infusions means that there are 5 grams of Dextrose dissolved in each 100ml of fluid, and this will remain the same if we have a 500ml infusion bag or a 1 litre infusion bag.
1 litre of 10% Dextrose means 10 gram Glucose in every 100 mL
Example-1,
Dextrose 50% injection in a 25ml vial. Patient prescribed 20g. How many mL?
50 % = 50 g in 100 mL
20 ÷ 50 x 100
Answer: 40 mL
Example-2,
Calcium Chloride 10% injection in a 10ml ampoule. How much is needed for a patient prescribed 2g?
10 % = 10 g in 100 mL
Apply formula,
Dose required ÷ Dose available x volume
2 ÷ 10 x 100 = 20 mL (i. e. 2 ampoules)
One in ….. concentration
This final type of concentration method is used only occasionally, e.g. tuberculin, adrenaline. 1 is stated as 1 in 100, 1 in 10,000, etc, and means grams in ml.
Thus: 1 in 100 means 1g in 100ml
1 in 1000 means 1g in 1000ml
1 in 10,000 means 1g in 10,000ml
Therefore, it can be seen that 1 in 1000 is a WEAKER strength that 1 in 100, and 1 in 10,000 is WEAKER than 1 in 1000.
Example: We want to give 1mg tuberculin using 1 in 1000 strength solution.
1 in 1000 strength solution means 1 g in 1000 Apply formula, Dose required ÷ Dose available x Volume its in 1mg ÷ 1000mg x 1000 = 1 mL Example-1, Give 1mg of epinephrine using the 1 in
10,000 solution. 1 in 10,000 means 1g in 10,000 mL, i.e. 1000 mg in 10,000 mL Apply formula, Dose required ÷ Dose available x Volume its in 1mg ÷ 1000mg x 10,000 = 10 mL Example-2, Give 5mg tuberculin using 1 in 100 solution 1 in 100 means 1g in 100 ml, in mg, 1000 mg in 100 mL Apply formula, Dose required ÷ Dose available x Volume its in 5mg ÷ 1000mg x 100