Sick day family hydration
Fever and stomach bugs dehydrate fast — especially in kids. Here's the protocol by illness type, and the line between home care and ER.
Quick answer
Sick day family hydration
For diarrhea or vomiting illness, oral rehydration solution (ORS) beats plain water. WHO/UNICEF low-osmolarity ORS (245 mOsm/L) supplies sodium and glucose that the gut absorbs together via the SGLT1 cotransporter (two sodium ions per glucose), pulling water across the intestinal lining — something plain water can't do. Give it in frequent small sips, not big gulps: for a child under 2, about 1 teaspoon every 1–2 minutes. Skip sports drinks and full-strength juice in significant illness — too much sugar, too little sodium. Seek care for red flags: no urine for 8+ hours, blood in stool or vomit, inability to keep fluids down, confusion, or sunken eyes with no tears.
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Sick days are when hydration protocols matter most and are hardest to execute. A feverish 3-year-old is not going to willingly drink 1 litre of fluids on command; a vomiting 8-year-old can't keep water down; a teen with the flu is just going to sleep. This page covers the hydration protocol by illness type: fever, stomach bug, cold/flu, and the combination of fever + vomiting (the highest-risk category). It includes the 'small frequent sips' rule that averts re-vomiting, when Pedialyte beats water, the red flags that mean urgent care, and the specific dehydration signs in sick kids that progress faster than parents expect.
By illness type
Fever alone: +200–300 ml per degree above normal per day
A kid with 102°F fever needs about 400 ml extra beyond baseline to replace fever-driven respiratory + sweat losses. Cold water or cold fruit can be more acceptable than warm.
Stomach bug (vomiting/diarrhea): Pedialyte, not plain water
Oral rehydration solution replaces the specific sodium + glucose lost in vomit/diarrhea. Plain water in this setting can worsen electrolyte imbalance.
Cold/flu: warm liquids + plain water alternating
Warm broth, tea with honey, chicken soup — both hydrating and soothing to irritated mucous membranes. Don't force plain water if warm is accepted.
Post-vomiting rehydration: small frequent sips
Wait 30 min after last vomit, then 5 ml every 5 min for 30 min. If that stays down, advance to 15 ml every 10 min. Rushing a big glass triggers re-vomiting.
Sick-kid hydration tactics
- Popsicles (fruit or Pedialyte) — hydration + throat comfort + accepted by sick kids
- Small cup (50–100 ml) refilled frequently, not big cup sat full
- Bendy straw — easier for a kid lying flat or propped up
- Track wet diapers or urination frequency — don't trust 'they had some water'
- For fever: cold drinks + cold fruit, even if you'd usually serve warm
- Offer fluids every 15 min while awake — set a timer if needed
- Re-introduce food only after fluids are holding down for 2+ hours
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Open the calculator →Dehydration signs during illness
Signs of Dehydration
- Fewer than 4 wet diapers/urinations in 24h while sick
- Dark yellow urine despite 'drinking something'
- Persistent vomiting (>6 hours) with no fluid retention
- Sunken eyes or sunken soft spot
- Dry mouth + no tears when crying
- Unusual lethargy — can't rouse, won't engage
- Cold mottled skin — emergency
When to Contact Your Healthcare Provider
- Vomiting >12 hours with no fluid retention — urgent care
- Fever >102°F + signs of dehydration — same-day pediatrician
- Any severe dehydration sign (sunken eyes, lethargy, cold skin) — ER
- Stomach bug + fever in a child under 12 months — ER for hydration assessment
- Bloody diarrhea or vomit — ER
Sources & Citations
- 245 mOsm/L (old: 311); sodium 75, glucose 75 mmol/L — WHO/UNICEF low-osmolarity oral rehydration solution (ORS) contains sodium 75 mmol/L, glucose 75 mmol/L, potassium 20 mmol/L, chloride 65 mmol/L, and citrate 10 mmol/L, totaling 245 mOsm/L — the reduced-osmolarity formula that replaced the older 311 mOsm/L version[1]
- 2 Na⁺ : 1 glucose — ORS works via SGLT1 glucose-sodium cotransport; without glucose, sodium is not absorbed and water does not follow osmotically — why plain water rehydrates poorly during diarrhea or vomiting[3]
- OR 0.61 (95% CI 0.47–0.81) — Reduced-osmolarity ORS lowers the need for unscheduled IV fluids versus standard WHO ORS in children with diarrheal dehydration[2]
- OR 0.71 (95% CI 0.55–0.92) — Reduced-osmolarity ORS reduces vomiting versus standard WHO ORS in children[2]
- high osmolarity; not recommended — Sports drinks, sodas, and full-strength juices have very high osmolarity (too much sugar, too little sodium) and are not ideal rehydration fluids in significant illness[4]
- treatment failure 16.7% vs 25.0%; index-visit IV 0.9% vs 6.8% — In mild childhood gastroenteritis with minimal dehydration, half-strength apple juice plus preferred fluids had fewer treatment failures than electrolyte solution (does NOT apply to moderate or severe dehydration)[5]
- 1 tsp every 1–2 min; 50–200 mL per stool — Give ORS as frequent small sips rather than large gulps — for a child under 2, about 1 teaspoon every 1–2 minutes; WHO guidance is roughly 50–100 mL (under 2) or 100–200 mL (ages 2–10) after each loose stool[6]
- no urine 8+ hrs; bloody stool/vomit; confusion — Red-flag dehydration signs requiring medical care: no urine or wet diaper for 8+ hours, blood in stool or vomit, inability to keep fluids down, confusion or dizziness, sunken eyes or no tears, or diarrhea lasting beyond 24–72 hours[6]
- [1]WHO/UNICEF new ORS 2006 — WHO/UNICEF. Oral Rehydration Salts: Production of the new ORS (WHO/FCH/CAH/06.1). 2006.
- [2]Hahn, Kim, Garner, BMJ 2001 — Hahn S, Kim Y, Garner P. Reduced osmolarity oral rehydration solution for treating dehydration caused by acute diarrhoea in children. BMJ. 2001;323(7304):81–85.PMID: 11451782
- [3]Buccigrossi et al., Sci Rep 2020 — Buccigrossi V, et al. Functional and metabolic effects of oral rehydration solution on intestinal mucosa. Sci Rep. 2020.PMID: 32385331DOI: 10.1038/s41598-020-64818-3
- [4]Chang JG, AAFP 2017 — Chang JG. Oral Rehydration Therapy. American Family Physician. 2017;96(11):700–701.
- [5]Freedman SB et al., JAMA 2016 — Freedman SB, et al. Effect of Dilute Apple Juice and Preferred Fluids vs Electrolyte Maintenance Solution on Treatment Failure Among Children With Mild Gastroenteritis: A Randomized Clinical Trial. JAMA. 2016;315(18):1966–1974.PMID: 27131100
- [6]Hartman et al., AAFP 2019 — Hartman S, et al. Dehydration: Diagnosis and Management. American Family Physician. 2019;99(3):159–165.
Medically reviewed: 2026-06-22. Every figure on this page is sourced to the named primary references above.
Frequently Asked Questions
My kid is vomiting. How do I rehydrate without triggering more vomiting?
The 5-5-30 rule: wait 30 minutes after the last vomit. Then give 5 ml (one teaspoon) of Pedialyte every 5 minutes for 30 minutes. If that stays down, advance to 10 ml every 10 min, then 15 ml every 15 min. Total rehydration to 'normal' volumes takes 2–4 hours done correctly. Rushing it — giving a big glass too soon — triggers another round of vomiting. Pedialyte is preferred over water for stomach bugs because it replaces the specific electrolytes vomit depletes.
Should I give my sick kid sports drinks?
For most pediatric illness settings, no — sports drinks have too much sugar (osmotic draw into the gut worsens diarrhea) and too little sodium (compared to Pedialyte) to be ideal. They can be a last resort when a kid refuses everything else but accepts Gatorade — diluted 50/50 with water is better than refusing fluids entirely. For vomiting/diarrhea specifically, stick with Pedialyte or generic oral rehydration solution. For plain fever or cold, plain water, broth, or watered-down juice is fine.
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