Can dehydration cause anxiety? What the research shows

When you’re anxious, it’s easy to forget to drink. And when you haven’t drunk enough, you can feel light-headed, tired and on edge, which makes anxiety harder to handle.

So can dehydration actually cause anxiety? The honest answer: it doesn’t cause an anxiety disorder, but it can bring on anxious feelings and make existing anxiety worse. Here’s what the research shows, and what to do about it.

What the research shows

• In men: in a controlled study, mild dehydration (losing about 1.5% of body weight in fluid) increased tension and anxiety and fatigue, and made some thinking tasks harder.
• In women: a similar study found mild dehydration worsened mood, made tasks feel harder, lowered concentration and brought on headaches.
• In everyday life: a large survey of adults in Iran found people who drank less than two glasses of water a day were more likely to have depression. There was a similar trend for anxiety, but it wasn’t statistically clear once other factors were taken into account. Surveys like this can only show a link, not cause and effect.

So the evidence suggests dehydration can nudge your mood towards tension and anxiety, especially in the short term. It’s one piece of the puzzle, not the whole story.

Why dehydration can feel like anxiety

Dehydration causes body feelings that overlap with anxiety:

• dizziness or light-headedness
• a faster heartbeat
• headaches
• tiredness and trouble concentrating
• a dry mouth

If you’re prone to anxiety, your brain may notice these and read them as a sign that something is wrong, which can set off worry or even panic.

It works the other way too. When you’re anxious, you may forget to drink, sweat more, breathe faster, drink more coffee or alcohol, or lose your appetite, all of which can leave you dehydrated.

Signs you might be dehydrated

The NHS lists these common signs:

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

You’re more likely to get dehydrated in hot weather, when you exercise, if you have a fever, vomiting or diarrhoea, if you drink a lot of alcohol, or as you get older.

How much should you drink?

There isn’t one number that’s right for everyone. The NHS suggests aiming for 6 to 8 cups or glasses of fluid a day, and more in hot weather or when you’re active. Water, milk, sugar-free drinks, tea and coffee all count, although caffeine can make some anxious people jittery.

A simple guide: drink regularly through the day, and aim for pale yellow pee.

More isn’t always better

Drinking far more water than your body needs, especially very quickly, can dilute the sodium in your blood. This is called hyponatremia, and it can be dangerous, causing nausea, headache, confusion and, in severe cases, seizures. It’s rare, but it can happen during long endurance events or when people force themselves to drink huge amounts.

If you have heart failure, kidney disease or another condition where your doctor has told you to limit fluids, follow their advice rather than general guidelines.

What helps

• Keep water nearby. A bottle on your desk or in your bag makes it easy to sip through the day.
• Drink with meals and snacks.
• Drink more when it’s hot, when you exercise and when you’re unwell.
• Go easy on alcohol, which makes you lose more fluid and can leave you anxious the next day.
• Watch the caffeine. Coffee counts towards your fluids, but too much can bring on jitters. Our post on whether caffeine causes anxiety explains more.
• Eat water-rich foods, like fruit, vegetables, soups and yoghurt.

If you’re anxious right now, a glass of cool water, sipped slowly, can help in another way too: it gives you something calm to focus on.

When to see a doctor

Get urgent medical help (call 911 in an emergency) if you or someone else has:

• confusion or unusual drowsiness
• a very fast heartbeat, or fainting
• not peed all day
• sunken eyes and very dry skin with any of the above
• signs of dehydration in a baby or older person who is unwell

See a doctor soon if you’re vomiting or have diarrhoea and can’t keep fluids down, or you feel thirsty all the time and pee a lot, which can be a sign of diabetes.

And if anxiety stays high even when you’re well hydrated, it deserves its own support. Our guide to anxiety and panic attacks is a good place to start.

Frequently asked questions

Can dehydration cause panic attacks?

It can contribute. Dizziness, a faster heartbeat and a dry mouth from dehydration can be read by an anxious brain as danger, which can tip into panic in people who are prone to it. Staying hydrated is one simple way to lower the odds.

Can drinking water help anxiety?

It won’t treat an anxiety disorder, but staying hydrated helps your body and mood work at their best. And slowly sipping cool water during anxious moments can be calming.

How quickly does rehydrating help?

Mild dehydration usually improves within minutes to an hour of drinking. If you still feel unwell, or symptoms are severe, get medical advice.

Can anxiety make you dehydrated?

Yes, indirectly. Anxiety can make you forget to drink, lose your appetite, sweat more and reach for coffee or alcohol, all of which can leave you low on fluids.

How Breatheasy can help

Breatheasy can help you notice the patterns behind your anxious days. Ten-second check-ins and a journal let you track how you feel alongside things like sleep, caffeine and how much you’ve been drinking. When anxiety spikes, tap “I’m feeling anxious” and Luma walks you through slow breathing and grounding. Breatheasy is coming soon to iPhone and Android.

Sources

• Mild dehydration impairs cognitive performance and mood of men, Ganio and others, British Journal of Nutrition, 2011
• Mild dehydration affects mood in healthy young women, Armstrong and others, Journal of Nutrition, 2012
• Drinking plain water is associated with decreased risk of depression and anxiety in adults, Haghighatdoost and others, World Journal of Psychiatry, 2018
• Dehydration, NHS
• Water, drinks and hydration, NHS
• Low blood sodium (hyponatremia), MedlinePlus, US National Library of Medicine