Nursing care
Oral Rehydration Therapy: the nurse's role, start to finish
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Oral rehydration therapy corrects mild to moderate dehydration by giving an oral rehydration solution in small, frequent volumes, roughly 50 to 100 mL per kilogram over four hours. Sports drinks are not a substitute, since their electrolyte and sugar content differs from the formulated solution the body needs.
Indications and contraindications
Oral rehydration therapy is indicated for mild to moderate dehydration from vomiting, diarrhoea, fever, or reduced intake, in patients who are alert enough to swallow safely and protect their airway. It is the preferred first-line approach over IV fluids in this population because it is less invasive, avoids catheter-related risks, and can often be managed at home under nursing guidance.
It is contraindicated in severe dehydration, shock, ileus, intractable vomiting, altered consciousness, or any condition that compromises the ability to swallow or absorb fluid through the gut. A patient with these findings needs IV rehydration and escalation, not a cup of oral solution and a plan to reassess in an hour.
Getting the patient ready
Assess the patient's hydration status, weight, level of alertness, and gag reflex before starting, and confirm there is no active vomiting that would defeat the purpose. Weigh the patient if possible, since the volume plan is calculated per kilogram and an outdated weight will misdirect the whole regimen.
Explain the plan in terms the patient or the parent will actually follow: small amounts, often, not a large glass swallowed in one go. Position the patient upright or semi-upright to reduce aspiration risk and nausea, and have an emesis basin within reach, since a patient who vomits mid-attempt needs to restart the volume slowly rather than push through.
Technique and safety checks
Give the oral rehydration solution in small volumes at frequent intervals, such as a teaspoon or 5 to 10 mL every few minutes, rather than allowing free access to a full glass. The total target is roughly 50 to 100 mL per kilogram of body weight delivered over four hours, adjusted to the degree of dehydration and the patient's tolerance.
Sports drinks are not a substitute for oral rehydration solution. Their sodium content is too low and their sugar content too high relative to the formulated electrolyte balance the body needs during dehydration, and using one in place of the correct solution can worsen the imbalance rather than correct it. If vomiting occurs, pause for 10 minutes, then resume at an even smaller volume rather than abandoning the plan.
What can go wrong
Vomiting from too-rapid administration is the most common setback and is managed by pausing and restarting smaller, not by switching fluids. Ongoing vomiting despite a slowed pace, or diarrhoea that outpaces intake, signals that oral therapy is failing and IV fluids should be escalated to before the patient deteriorates further.
Electrolyte imbalance can still occur if a non-standard fluid is used or if the solution is diluted or concentrated incorrectly at home, so check that any caregiver preparing it at home is reconstituting according to the packet instructions rather than by eye. Aspiration is a risk in a lethargic or uncooperative patient, which is why altered consciousness is a contraindication rather than a reason to go slower.
Ongoing care
Track intake against the calculated target and monitor output, including nappy counts in infants or voiding frequency in older patients, as the clearest sign that rehydration is succeeding. Reassess hydration signs, alertness, and weight at intervals appropriate to the setting, and document the volume tolerated versus the volume given.
Adjust the pace based on tolerance rather than the clock alone; a patient tolerating the solution well can move to slightly larger, less frequent volumes as the four-hour window progresses, while one who is struggling needs the plan slowed and reassessed. Reinforce to the patient or caregiver that improvement is measured by wet nappies, alertness, and reduced thirst, not by finishing the full calculated volume on a fixed schedule.
Common exam questions
Expect scenarios that test whether you can identify a contraindication, such as a lethargic child or a patient with intractable vomiting, as the reason to escalate to IV fluids rather than continue oral therapy. Also expect a question asking you to correct the misconception that a sports drink is an adequate substitute for oral rehydration solution.
Volume and pacing questions are common: identifying that small, frequent amounts are correct and that a large volume given at once risks vomiting, or calculating whether a given intake meets the 50 to 100 mL per kilogram target over four hours. A question may also ask for the priority nursing action when a patient vomits during oral rehydration, where the correct answer is to pause briefly and resume at a smaller volume rather than stop the plan entirely or switch to an unapproved fluid.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our pediatrics practice questions are the closest set to what this page covers.
Common questions
How much oral rehydration solution should a dehydrated patient receive?
Roughly 50 to 100 mL per kilogram of body weight over four hours, given in small, frequent volumes rather than large amounts at once. The exact target depends on the degree of dehydration and how well the patient tolerates it.
Can sports drinks be used instead of oral rehydration solution?
No. Sports drinks have too little sodium and too much sugar compared to the formulated electrolyte balance in oral rehydration solution, and substituting one can worsen the fluid and electrolyte imbalance rather than correct it.
What should a nurse do if a patient vomits during oral rehydration therapy?
Pause administration for about 10 minutes, then resume with a smaller volume than before. Vomiting usually means the fluid was given too fast, not that oral therapy has failed outright.
When is oral rehydration therapy contraindicated?
In severe dehydration, shock, intractable vomiting, ileus, or altered consciousness that compromises safe swallowing. These situations call for IV rehydration and escalation rather than continued oral attempts.
How do I know if oral rehydration therapy is working?
Improved alertness, reduced thirst, and increased urine output or wet nappies are the clearest signs. Track intake against the calculated volume target, but judge success by these clinical signs rather than by completing an exact number.