Chapter 3 · Water
Dehydration: recognize it in time
Gauge your hydration by your urine: clear or pale yellow is a good sign; dark, scant, or strong-smelling means you need to drink. FM 21-76 describes the progression by percentage of body fluid lost:
| Fluid loss | Symptoms | What to do |
|---|---|---|
| 5 % | Thirst, irritability, nausea, weakness | Drink now, in sips. Rest in the shade. |
| 10 % | Dizziness, headache, inability to walk, tingling in arms and legs | Emergency. Complete rest, water with oral rehydration solution, cool the body, seek medical help. |
| 15 % | Blurred vision, pain when urinating, swollen tongue, deafness, numb skin | Risk of death. Call 911. |
| More than 15% | Can cause death | — |
Thirst comes late: in heat and with exertion, drink even if you aren't thirsty. For heat stroke and heat exhaustion, see chapter 7 (first aid) and chapter 10 (extreme heat).
