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Macronutrient

Water

total, from drink + food

Temperature regulation, nutrient transport, waste removal, joint lubrication

Essential nutrient

Reference intakes (RDA or AI) are set by the National Academies of Sciences, Engineering, and Medicine. Deficiency thresholds come from clinical and WHO guidance.

At a glance

Women, 19-50
2.7 L/day (AI, all sources)
Men, 19-50
3.7 L/day (AI, all sources)
Upper limit (adults)
Not established (overhydration can cause hyponatremia)
How common is deficiency?
COMMON mild dehydration, especially in older adults and in hot climates

Food sources

Animal sources
Milk, broth, fish, meat (small share)
Plant sources
Fruits and vegetables (cucumber, watermelon, lettuce, oranges), soups, herbal teas

Deficiency and testing

Signs of deficiency
Thirst, dark urine, dry mouth, headache, dizziness, fatigue, constipation, low blood pressure, confusion
Who is at higher risk
Older adults, infants, athletes, outdoor workers, people with diarrhea/vomiting/fever, diabetes
How it is tested
Serum osmolality; BUN:creatinine ratio; serum sodium; urine specific gravity / osmolality; urine color chart
Cut-offs
Serum osmolality >295 mOsm/kg; urine specific gravity >1.020-1.030; BUN:creatinine >20:1

Symptoms are not specific. Only a clinician with the right tests can tell whether you are deficient.

Supplement forms

Common forms
plain water, oral rehydration solution (ORS), electrolyte drinks/powders, sports drinks, coconut water, water-rich foods, IV fluids (clinical).
More effective
plain water for daily needs; ORS (glucose + sodium) for diarrhea, vomiting, or heavy sweat; water-rich foods (fruits, vegetables, soups) contribute about 20% of intake.
Less effective
sugary sodas and high-sugar juices for rehydration (can worsen diarrhea); caffeinated or alcoholic drinks as the main fluid; drinking very large volumes of plain water quickly (hyponatremia).

Safety, interactions and halal notes

Safety and interactions
Upper limit for adults: Not established (overhydration can cause hyponatremia). Going above the upper limit over time can cause harm, so check labels and talk to a clinician before high-dose supplements.
Halal note
The nutrient itself is not a halal question. For supplements, check the delivery form: gelatin (pork or non-halal bovine), capsule shells, glycerin, and alcohol-based carriers need halal certification. Ask for the halal certificate, not just a label claim. This is general guidance, not a certification.

Frequently asked questions

How much Water do adults need per day?

Women 19-50: 2.7 L/day (AI, all sources). Men 19-50: 3.7 L/day (AI, all sources). Upper limit: Not established (overhydration can cause hyponatremia). Needs change with age, pregnancy and health conditions.

What are the signs of Water deficiency?

Thirst, dark urine, dry mouth, headache, dizziness, fatigue, constipation, low blood pressure, confusion. These signs are not specific, so only a clinician with the right tests can confirm a deficiency.

What are the best food sources of Water?

Animal sources: Milk, broth, fish, meat (small share). Plant sources: Fruits and vegetables (cucumber, watermelon, lettuce, oranges), soups, herbal teas.

Which form of Water supplement is best?

plain water for daily needs; ORS (glucose + sodium) for diarrhea, vomiting, or heavy sweat; water-rich foods (fruits, vegetables, soups) contribute about 20% of intake.

Sources

  1. National Academies: Dietary Reference Intakes

← Back to the full nutrient guide

This page is for education only and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Supplements are not intended to diagnose, treat, cure or prevent any disease. Talk to a qualified clinician before starting a supplement, especially if you are pregnant, breastfeeding, take medicine or have a medical condition. Daily needs are US reference intakes for adults 19-50.

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