Grading dehydration by clinical signs
No single sign is reliable; grade on the constellation. The most useful individual predictors of significant (≥5%) dehydration are prolonged capillary refill, abnormal skin turgor, and abnormal respiratory pattern.
| Sign | None / mild (<5%) | Some / moderate (5–10%) | Severe (>10%) |
|---|---|---|---|
| General condition | Alert | Restless, irritable | Lethargic, floppy, ↓consciousness |
| Eyes | Normal | Slightly sunken | Deeply sunken |
| Tears | Present | Reduced | Absent |
| Mucous membranes | Moist | Dry | Parched |
| Thirst | Normal | Eager to drink | Drinks poorly / unable |
| Skin pinch | Recoils instantly | Recoils slowly | Recoils very slowly (>2 s) |
| Capillary refill | <2 s | 2–3 s | >3 s |
| Pulse / HR | Normal | Tachycardia | Tachycardia → weak/thready |
| Urine output | Normal | Reduced | Minimal / anuric |
| Eyes/fontanelle | Normal | Sunken | Markedly sunken |
Weight loss is the gold standard: % dehydration = (pre-illness weight − current weight) / pre-illness weight × 100. A recent reliable weight beats any clinical estimate.
Estimating the fluid deficit
Deficit (mL) = % dehydration × body weight (kg) × 10
| % dehydration | Deficit per kg |
|---|---|
| 5% | 50 mL/kg |
| 10% | 100 mL/kg |
| 15% | 150 mL/kg |
Example: a 12 kg child estimated at 8% → 0.08 × 12 × 1000 = 960 mL deficit. Replace on top of maintenance plus ongoing losses — see Maintenance Fluid Calculator.
Oral vs IV rehydration
| Oral rehydration (ORS) | IV rehydration | |
|---|---|---|
| Indication | Mild–moderate, child alert and able to drink | Severe dehydration, shock, persistent vomiting, ileus, ↓consciousness, failed oral trial |
| Fluid | Low-osmolarity ORS (WHO 75 mmol/L Na) | Isotonic crystalloid (0.9% saline / Ringer’s lactate) |
| Some dehydration | ~50–100 mL/kg over 4 h, then reassess | — |
| Severe | — | 20 mL/kg bolus, repeat to reverse shock; then replace remaining deficit over 24–48 h |
- ORS is first-line for mild–moderate dehydration (WHO, NICE) — as effective as IV with fewer complications. Give in small frequent amounts; nasogastric ORS is an option before IV.
- Continue age-appropriate feeding/breastfeeding throughout; replace ongoing stool losses (~10 mL/kg per loose stool).
- Hypernatraemic dehydration (Na >150): rehydrate slowly to avoid cerebral oedema — aim to drop sodium ≤0.5 mmol/L/hr (≤10–12 mmol/L/day). Estimate the water gap with the Free Water Deficit Calculator.
Red flags for escalation
Shock (cool peripheries, weak pulse, hypotension is a late sign), altered consciousness, bilious vomiting, suspected surgical abdomen, or failure to improve on adequate ORS — move to IV and senior review.
Decision support for qualified clinicians only — verify against current primary guidelines and your clinical judgement.