Nursing care
Percent Solutions, explained for the bedside and the exam
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
A percent solution states grams of solute per 100 mL of solution. A 5 per cent solution is 5 grams in 100 mL; dextrose 50 per cent is 25 grams in a 50 mL syringe. Every percent solution question is a ratio question wearing different units, and the arithmetic is the whole task.
Defining it precisely
A percent solution is grams of solute per 100 mL of solvent or solution, expressed as w/v per cent for solids in liquid. Read 5 per cent as 5 grams in 100 mL. Read 0.9 per cent sodium chloride as 0.9 grams in 100 mL, which is why normal saline carries 9 grams of sodium chloride per litre. The percentage is not a proportion of the drug's strength against some other reference; it is a fixed ratio to a 100 mL base, and every calculation starts from that ratio.
Dextrose 50 per cent, the syringe used for symptomatic hypoglycaemia, is 25 grams in a 50 mL syringe. Work it from the definition: 50 grams per 100 mL, halved because the syringe holds 50 mL, gives 25 grams. That single fact anchors most of the questions written around this drug, and it is worth holding in memory rather than recalculating from a formula sheet under time pressure.
The exceptions that matter
Not every percentage on a label means grams per 100 mL. Volume-in-volume percentages, used for one liquid diluted in another, express millilitres of solute per 100 mL of solution, not grams. Weight-in-weight percentages, seen in some topical preparations, express grams of solute per 100 grams of product. A 1 per cent hydrocortisone cream is 1 gram of hydrocortisone per 100 grams of cream, not per 100 mL, because cream has no meaningful volume to measure against.
The other exception is concentration expressed as a ratio rather than a percentage, such as epinephrine 1:1000 or 1:10,000. These convert to percentage form, 1:1000 equals 0.1 per cent, but nurses who treat all drug strengths as interchangeable percentages will misplace a decimal. Check the unit printed on the label before applying the 100 mL rule, and never assume w/v as a default for every preparation.
Using it to prioritise
Concentration itself is a clinical signal. A more concentrated solution delivers more solute in less volume, which matters for fluid-restricted patients, for peripheral versus central line selection, and for the speed of an intended effect. Hypertonic saline at 3 per cent is chosen over 0.9 per cent precisely because a smaller volume carries a larger osmotic pull, useful in severe hyponatraemia where fluid overload is a real risk.
When an exam item asks which patient should be assessed first after a percent-solution infusion starts, the reasoning usually runs through concentration and rate together. A hypertonic solution running at a standard rate can cause more rapid fluid shifts than an isotonic one at the same rate, so the patient receiving the higher-percentage solution is the one to reassess sooner, particularly for neurological status and serum sodium trend.
Traps in exam wording
Item writers exploit the gap between per cent and per millilitre. A question may give a total volume and a percentage, then ask for total grams, or give total grams and a percentage, then ask for volume, deliberately reversing the direction candidates are used to working in. Always identify what the question gives and what it asks for before applying the 100 mL relationship, rather than pattern-matching to the last similar question.
Another trap mixes w/v and v/v percentages in the same stem, expecting the candidate to notice the label says mL rather than g. A third asks the candidate to compare two percentages of different drugs and infer which is more concentrated in absolute terms, which is meaningless without knowing the volume each is dispensed in. Read every value with its unit attached, not as a bare number.
Examples from practice
A nurse draws up dextrose 50 per cent for a patient with a blood glucose of 2.1 mmol/L and altered consciousness. The full 50 mL syringe delivers 25 grams of dextrose, consistent with local protocol for symptomatic hypoglycaemia, and the nurse documents blood glucose before and after administration alongside the mental status response.
A second example: an order for 3 per cent sodium chloride at 100 mL over one hour is written for severe symptomatic hyponatraemia. The nurse recognises that 3 per cent contains 3 grams per 100 mL, roughly three times the sodium concentration of normal saline in the same volume, and anticipates the need for frequent serum sodium checks and slow correction to avoid osmotic demyelination.
Summary
A percent solution is grams per 100 mL for weight-in-volume preparations, and dextrose 50 per cent supplies 25 grams in its standard 50 mL syringe. Confirm whether a given percentage is w/v, v/v, or w/w before calculating, because the base unit changes the answer entirely.
Concentration carries clinical weight beyond arithmetic: it predicts fluid shift, informs line choice, and shapes monitoring priorities after administration. Treat every percentage as a ratio to be checked against its stated unit, not a number to be recalled by habit.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our dosage calculation and lab values practice questions are the closest set to what this page covers.
Common questions
How many grams are in dextrose 50 per cent?
A 50 mL syringe of dextrose 50 per cent contains 25 grams of dextrose, calculated as 50 grams per 100 mL halved for the 50 mL volume. This is the standard IV push dose for symptomatic hypoglycaemia in many protocols, though local policy governs exact indication and rate.
Is a percent solution always grams per 100 mL?
Only for weight-in-volume preparations. Volume-in-volume solutions express millilitres of solute per 100 mL of solution, and weight-in-weight preparations, such as some creams, express grams per 100 grams of product. Check the label's stated unit before assuming w/v.
Why is 0.9 per cent saline called normal saline?
0.9 per cent sodium chloride contains 9 grams of sodium chloride per litre, an osmolality close to plasma, which is why it is termed isotonic or normal. Concentrations above this, such as 3 per cent, are hypertonic and draw fluid osmotically.
How do I convert a ratio strength like 1:1000 to a percentage?
A ratio of 1:1000 means 1 gram in 1000 mL, which equals 0.1 grams per 100 mL, or 0.1 per cent. Divide the ratio's second number by 10 to get the equivalent w/v percentage, and double-check the decimal placement, since this is a common source of tenfold dosing errors.
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