What causes dehydration?
Most of us know that we should drink enough water to stay healthy and avoid dehydration. But dehydration isn’t just about forgetting to top up your glass. It’s about a balance of intake and usage.
When your body loses more fluids than it takes in, even slightly, that balance shifts. The effects aren’t often dramatic at first, which means you might not realise straightaway that you’re becoming dehydrated – meaning it can easily get worse before you act.
Below, we discuss what dehydration is and common ways it can come about to help you understand how to prevent it.
What is dehydration?
Dehydration occurs when your body doesn’t have enough fluid to carry out its normal functions properly.¹ Water is essential to almost every system in the body.
It helps to:
- Regulate body temperature
- Transport nutrients and oxygen
- Support digestion
- Remove waste products
- Maintain healthy circulation.
Fluids also work alongside important minerals known as electrolytes, including sodium, potassium and magnesium.² These minerals help to maintain fluid balance and support normal nerve and muscle function.
When fluid levels drop, your electrolyte balance can be affected. One of the most familiar signs people notice is a headache. Even mild dehydration can temporarily influence circulation and brain function, which may contribute to this feeling.³
Water also acts as a natural lubricant, meaning that it cushions joints and supports tissues throughout the body. Because of this, if you’re often dehydrated, making sure you’re drinking enough water can be a simple way to improve your joint health over time.
In many cases, dehydration is mild and easily corrected. However, repeated or ongoing dehydration can leave you feeling tired, unfocused or below your usual energy levels. Supporting your fluid intake alongside adequate mineral intake – such as with supplements like those found in our minerals range – can help to maintain your overall fluid balance.
What would cause dehydration?
At its simplest, dehydration usually happens for one of two reasons:¹
- You have not consumed enough fluids.
- You have lost more fluids than usual.
Sometimes, both occur at the same time – you’re losing too much for one reason and haven’t drunk enough water to suit your baseline needs.
Certain situations can increase fluid loss or raise your body’s need for water, making it important to drink more to compensate. Below are some of the most common causes to watch out for.
Vomiting and/or diarrhoea
Unpleasant to deal with in any circumstances, vomiting and diarrhoea can also cause rapid fluid loss over a short period.⁴ Because fluids leave the body quickly, it can be difficult to replace them fast enough. Along with water, the body also loses electrolytes when this happens, which is why it’s important to have something to eat if you can as well as replenishing your fluids.
In most healthy adults, vomiting and diarrhoea are rare and temporary experiences. However, young children and older adults may be more vulnerable and anyone should seek medical advice if symptoms persist.
Heatstroke
In hot weather, the body sweats to cool itself. Sweating is essential for temperature regulation, but it increases fluid loss.⁵
If those fluids are not replaced, dehydration can develop quickly. In more serious cases, heat exhaustion or heatstroke may occur, which requires urgent medical attention. This type of dehydration is usually short term but can become severe if not managed promptly.
As a general rule of thumb, you should always try to drink more water during periods of hot weather.
Overindulgence in alcohol
Alcohol increases urine production, which leads to greater fluid loss.⁶ It can also reduce your awareness of thirst, meaning you might not realise you’re thirsty. This makes it less likely that you’ll replace the fluids you lose before dehydration sets in.
This is one reason why dehydration contributes to common hangover symptoms such as headaches and fatigue. For most people, this effect is temporary and improves once fluids are restored.
Intense physical activity
During exercise, especially prolonged or high-intensity sessions, the body loses fluid through sweat.⁷ The more intensely you exercise, the more you’ll sweat – and remember that these effects can be compounded by other factors such as warmer weather.
If fluid intake does not match loss during exercise, dehydration can affect physical performance and recovery. This is generally short term and manageable by increasing fluid intake before, during and after activity.
Some minor illnesses
Even minor illnesses can increase fluid needs. A fever raises body temperature and increases fluid loss, while fatigue or a sore throat may reduce your desire to drink.⁸
In most cases, this effect is temporary. Increasing fluid intake when unwell can help to reduce the risk of dehydration, so you’re less likely to experience dehydration symptoms on top of your illness.
Certain medications
Some medications, particularly diuretics, increase urine output.⁹ While this can be necessary for managing certain health conditions, it also increases fluid loss.
If you’re taking prescription medication and aren’t sure how it affects hydration, you can speak to a doctor or pharmacist about your specific medication and its effects. Never stop taking a medication without consulting your doctor first.
Diabetes
Diabetes can increase the risk of dehydration, particularly when blood glucose levels are high.¹⁰ Elevated blood sugar causes the kidneys to remove excess glucose through urine, leading to increased urination and fluid loss.
If not properly managed, this can contribute to ongoing dehydration. Monitoring and medical support are important for maintaining fluid balance in this situation, as well as for treating other symptoms of the condition.
A balanced approach to hydration
Dehydration isn’t always dramatic. It often develops gradually and can be influenced by everyday factors such as exercise, illness, alcohol intake or medications.
By understanding the common causes of dehydration, you can make simple adjustments when needed and support your body’s natural balance more effectively.
References
- NHS. (2022). Dehydration.
https://www.nhs.uk/conditions/dehydration/ - Harvard T.H. Chan School of Public Health. (n.d.). Water and hydration.
https://www.hsph.harvard.edu/nutritionsource/water/ - Mayo Clinic. (2023). Dehydration: Symptoms and causes.
https://www.mayoclinic.org/diseases-conditions/dehydration/symptoms-causes/syc-20354086 - NHS. (2022). Diarrhoea and vomiting.
https://www.nhs.uk/conditions/diarrhoea-and-vomiting/ - NHS. (2022). Heat exhaustion and heatstroke.
https://www.nhs.uk/conditions/heat-exhaustion-heatstroke/ - NHS. (2022). Alcohol misuse.
https://www.nhs.uk/conditions/alcohol-misuse/ - British Nutrition Foundation. (2021). Hydration and physical performance.
https://www.nutrition.org.uk/putting-it-into-practice/hydration/ - NHS. (2023). Fever in adults.
https://www.nhs.uk/conditions/fever-in-adults/ - NHS. (2022). Diuretics.
https://www.nhs.uk/conditions/diuretics/ - Mayo Clinic. (2023). Hyperglycaemia (high blood sugar).
https://www.mayoclinic.org/diseases-conditions/hyperglycemia/symptoms-causes/syc-20373631
