Can dehydration cause confusion?

Can dehydration cause confusion?

5 min read |
Alistair Clay Author

Author 14.01.2023

Alistair Clay

It's not usual for older people to become forgetful and sometimes confused, it happens to the best of us.

​​There can be many causes, but there's one that we often overlook - dehydration.

Can dehydration cause confusion?

Yes it can but the symptoms of dehydration can be subtle, or can get mistaken for other conditions which cause confusion.

If you care for an elderly loved one, then it's important you know the symptoms of dehydration and how it can cause confusion.

Here’s a summary of what we’ll cover:

  • Dehydration is when the body loses more fluid than it gains. This can upset the balance of minerals that the body needs for essential functions. 
  • Older people are especially at risk due to physical and lifestyle factors such as reduced kidney function or certain medications.
  • Dehydration can cause confusion as brain cells aren’t able to function properly.
  • If this continues over a prolonged period, brain cells shrink in size and mass, reducing overall function.
What is dehydration

What is dehydration?

Dehydration occurs when the body loses more fluid than it gains. 

This leaves the body unable to function normally for internal processes.

When dehydration occurs, the fine balance of minerals that the body needs becomes dysregulated. 

Alongside these invisible internal processes, it’s easy to forget that the body is made up of two-thirds water. 

Why is water important?

Water is essential for various organs and aspects of the body that we take for granted.

We need water to function for processes such as:

  • Lubricating joints and eyes to keep them moving
  • Aiding digestion
  • Flushing out waste and toxins
  • Keeping skin healthy

Categories of dehydration

Dehydration is classified into three categories by medical practitioners.  

First on the scale is ‘no dehydration’. This means that the body is hydrated, healthy and able to function normally in regard to water content. 

The next stage is referred to as ‘some’ dehydration. 

Patients with ‘some’ or ‘mild’ dehydration are not as critically ill as those with ‘severe’ dehydration. 

Though they are at high risk of becoming so. 

Can dehydration cause confusion?

They may be experiencing symptoms such as dark urine, dry mouth and tongue and feeling thirsty.

When an older adult starts feeling thirsty, they are already mildly dehydrated. 

Medical advice suggests that patients with some dehydration should be treated and monitored to ensure rehydration.

Mild dehydration needs to be addressed quickly and safely to prevent severe dehydration which can cause confusion or delirium. 


Are you worried about a loved one?

Early signs of dementia free guide

Severe dehydration

This is classed as a medical emergency as severe dehydration can cause damage to the kidneys, heart, and brain. 

Severely dehydrated people may need to be treated in hospital as their life could be at risk. 

Alongside the more common symptoms of dehydration, they may experience confusion and rapid heartbeat or breathing.

There’s more here on the symptoms of dehydration in the elderly.

Is dehydration caused by confusion

What are the risk factors for dehydration?

Dehydration can occur at any age and pose a health risk.

However, in elderly adults there are a few specific reasons why dehydration might occur.

Age-related physical changes

Kidney function deteriorates with age which has an effect on the body’s ability to conserve water.

To conserve water and regulate sodium levels, urine becomes more concentrated in elderly people.

The buildup of bacteria as a result of this can lead to urinary tract infections and cause further problems, including confusion. 

This is one of the reasons why dehydration can cause confusion in elderly people. 

Muscle mass and dehydration

Another age-related physical change is that muscle mass is significantly reduced in older people.

Muscles run all over the body and play an important role in storing water in the body.

Reduced mass means they are less able to store water which increases risk of dehydration.


What are the symptoms of dehydration

Medical conditions

In addition to these physical factors, some medical conditions can increase the risk of dehydration.

They might be worried about bladder issues, access to a toilet, or are unable to move around easily.

In these cases, elderly adults may modify their behaviour to avoid too many bathroom trips throughout the day and night. 

They might reduce the amount of liquids drunk to avoid discomfort or accidents, or hold their urine which causes other problems.

What are the risk factors for dehydration


Some medications can increase the risk of dehydration. 

Common examples include:

  • Laxatives for Constipation
  • Oral Medications for Type 2 Diabetes
  • Loop-Acting Diuretics for Heart Failure
  • Potassium-Sparing and Thiazide Diuretics for High Blood Pressure
  • Chemotherapy Drugs for Cancer

Many elderly people take medication which requires a drink to wash it down.

But this could be the only time they drink water if left unmonitored.

And remember women at any age, but especially the elderly are at greater risk of dehydration due to having higher fat content than men.

Can dehydration cause confusion?

The simple answer to this question is yes.

Dehydration can cause confusion and even delirium in elderly people.

This is because decreased water levels in the brain don’t allow brain cells to function as they should. 

Some studies suggest that being 1% dehydrated is enough to experience a 5% decrease in cognitive function.

Furthermore, a 2% decrease in brain hydration can result in short term memory loss. 

Inhibiting cognitive function and short-term memory are hallmarks of confusion that pose a concern for carers.

Severe dehydration in elderly

So how do we know dehydration can cause confusion?

A study conducted in 2018 found that for elderly people, ongoing ‘cellular stress of dehydration may promote continued cognitive decline.’ 

This continued cognitive decline posed potential links between prolonged dehydration and dementia in elderly people.

It went on to suggest that for people over the age 65, dehydrated individuals were at higher risk for dementia, while individuals with dementia were at higher risk for dehydration. 

This is because decreased water levels at a cellular level can inhibit the normal function of proteins. 


can medication cause dehydration

The brain and dehydration

Inhibited function can prevent the clearance of any toxic proteins, therefore allowing them to build up in the brain. 

These buildups of toxins damage brain cells and can be severe risk factors for Alzheimer’s disease, dementia with Lewy bodies and frontotemporal dementia.

This being said, there is not enough evidence to suggest that dehydration is an explicit cause of dementia. 

Read our articles on types of dementia care and ‘what are the early signs of dementia‘ for more information on these topics. 

Are you worried about a loved one?

Early signs of dementia free guide

How to prevent dehydration in someone you care for

As a carer, you can keep an eye on their fluid intake, which they may not be aware of themselves.

You can help them to stay hydrated by:

  • offering water and beneficial fluids rather than sugar or alcohol 
  • ensuring they drink at mealtimes
  • having a cup of tea as while chatting or doing something together 
  • offering food with a high water content, such as soup, jelly and water rich fruit and veg

If an elderly person begins to act differently or disorientated, you may find that dehydration causes confusion. 


symptoms of dehydration in elderly

Take on fluids safely

This can be done through water and other drinks, but also through water-rich foods like melon, cucumber, soups and dementia jelly drops. 

Remember that in order to stay hydrated, you must drink enough to replenish lost water in the body. 

As a general rule, adults should drink 6-8 large glasses of water a day. This equates between 1.2L to 2L throughout the day. 

The only side effect of drinking this healthy amount of water is needing to use the bathroom more. 

But the small inconvenience of that far outweighs the much worse effect of dehydration for elderly people. 


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Alistair Clay Author

Author 14.01.2023

Alistair Clay

Alistair is a founding Director of Sweet Pea Care and the Managing Director of social care communications agency Arc Seven where he advises some of the UK’s biggest care providers.