Signs you’re not drinking enough water

The common signs

The NHS lists these signs of dehydration in adults and children:

• feeling thirsty
• a headache, or feeling light-headed
• dark yellow, strong-smelling pee
• peeing less often than usual
• feeling dizzy
• feeling tired
• a dry mouth, lips and tongue
• sunken eyes

Mayo Clinic adds being confused to its list for adults — a sign that dehydration has become more serious.

The easiest check: colour

The simplest everyday test is the colour of your pee. The NHS advises drinking enough during the day that it’s pale; Mayo Clinic describes colourless or light yellow as the sign you’re getting enough. Dark yellow and strong-smelling means it’s time to drink.

What mild dehydration does to your day

Even a small shortfall may take the edge off your day. In a 2012 study, 25 young women who had lost about 1.4% of their body weight in water (through exercise, some with a diuretic) reported worse mood, found tasks harder, concentrated less well and had more headaches — although most measures of their thinking weren’t affected. A similar 2011 study of 26 young men, at about 1.6%, found poorer vigilance and working memory, and more tension and tiredness.

Keep that in proportion. These were small studies of young, healthy people dehydrated by exercise, and three of their authors worked for Danone, which sells bottled water (the 2011 study was funded by it). A 2018 review of 33 studies found dehydration’s effect on thinking to be small, and clearer once people had lost more than 2% of their body weight. The reasonable takeaway: staying topped up is an easy way to avoid feeling needlessly flat or headachy — not a productivity hack.

When to get help

If you’re mildly dehydrated, start by drinking more fluids. A pharmacist can recommend an oral rehydration solution (ORS): a powder you mix with water and drink.

The NHS advises seeing a doctor urgently if:

• you feel unusually tired, or a child seems drowsy
• you feel dizzy when you stand up and it doesn’t go away
• you have dark yellow pee or are peeing less than normal (or a baby has fewer wet nappies)
• you or your child are breathing quickly or have a fast heart rate
• a baby or child has few or no tears when they cry
• a baby has a soft spot on their head that sinks inwards

Get emergency help — in India, call 112 — if someone:

• has blue, grey, pale or blotchy skin, lips or tongue
• has skin that feels cold
• has difficulty breathing, or is taking lots of quick breaths
• is confused
• is sleepier than normal or difficult to wake

In a heatwave, India’s health ministry says to call 112 immediately for anyone with a high body temperature who is unconscious, confused or has stopped sweating: heatstroke is a medical emergency.

Preventing it

• Drink regularly through the day, and more when it’s hot or you’re active — see how much to drink.
• Keep your pee pale.
• When you’re already dehydrated, skip caffeinated drinks and alcohol.
• In a heatwave, drink even if you’re not thirsty — read staying hydrated in hot weather.