Dehydration happens when your body loses more fluids than you take in, disrupting nearly every system you depend on. Most people only notice it when thirsty — but by then, you're already 2% dehydrated.

1. Persistent headache — Your brain is 75% water. When dehydrated, it temporarily contracts, pulling away from the skull and triggering pain.

2. Dark yellow urine — Pale straw color means you're hydrated. Dark amber signals concentration and a clear warning to drink water.

3. Dry mouth and bad breath — Saliva has antibacterial properties. Less water means less saliva, leading to bacterial overgrowth.

4. Fatigue and brain fog — Even mild dehydration reduces cognitive performance, memory, and attention by up to 12%.

5. Muscle cramps — Electrolyte imbalance from water loss causes sudden, painful muscle contractions, especially during exercise.

6. Dizziness when standing — Dehydration lowers blood volume, causing temporary drops in blood pressure when you stand up quickly.

7. Dry, flaky skin — Skin is your body's largest organ. Insufficient hydration reduces elasticity and accelerates aging.

8. Constipation — Your colon pulls water from stool when dehydrated, leading to harder, more difficult bowel movements.

9. Rapid heartbeat — To compensate for reduced blood volume, your heart beats faster to maintain circulation.

10. Sugar cravings — The liver needs water to release glycogen. Without it, your body craves quick sugar fixes.

The fix? Drink 8-10 glasses (2-2.5 liters) daily. Add more if you exercise, live in hot climates, or consume caffeine and alcohol.