Hydration: How Much Water You Really Need and Practical Tips

Feeling tired, lightheaded, or just off your game? You might be under-hydrated. Hydration affects energy, digestion, skin, and how some medicines work. Below are clear, usable tips so you can stay steady all day without overthinking it.

How much to drink — a simple rule

Forget strict rules like "8 glasses" that don't fit everyone. A good starting point is about 30–35 mL per kilogram of body weight per day. That’s roughly 2–3 liters (about 8–12 cups) for most adults. If you weigh 70 kg (155 lb), aim for roughly 2.1–2.5 L daily.

Use urine color as a quick check: pale straw is good, dark yellow means drink more. Thirst is useful too — but it’s not perfect, since you can be slightly dehydrated before you notice it.

Smart hydration for meds, exercise, and illness

Some medicines change how much fluid you need. Diuretics, certain blood pressure meds, and some diabetes drugs can increase fluid loss. Other medicines, especially those that affect the stomach or cause diarrhea, raise your risk of dehydration. If you take regular meds, ask your pharmacist whether you should drink more water or watch electrolytes.

When you exercise, sweat removes both water and salts. For light workouts, plain water is fine. For long or intense sessions over an hour, use a sports drink or add a small snack with salt to replace electrolytes. If you’re sick with vomiting or diarrhea, use an oral rehydration solution — these restore the right balance of sugar and salt faster than water alone.

Special groups need extra care. Older adults don’t feel thirsty as clearly and should sip water regularly. Babies and young kids can lose fluids quickly; watch wet diapers and skin elasticity. People with kidney disease or heart failure should follow personalized fluid limits from their doctor.

Small habits add up. Carry a bottle, set reminders, drink a glass when you wake up and with meals, and choose foods that help—fruits like watermelon, cucumbers, soups, and yogurt. Limit alcohol and very sugary drinks; they can increase fluid loss or mess with blood sugar.

Electrolytes matter but don’t overdo them. Most people eating a normal diet get enough sodium and potassium. Use electrolyte drinks when you sweat heavily, have prolonged illness, or after intense endurance events.

Finally, if you notice dizziness, very dark urine, rapid heartbeat, confusion, or fainting, seek medical help. Those can be signs of moderate to severe dehydration that needs quick treatment.

Want a personalized tip? Tell your age, typical activity level, and any daily medications, and you’ll get simple steps to match your routine.