Dr Sarah Jarvis is the Clinical Director of the Patient Platform, an active medical writer, broadcaster, and the resident doctor for BBC Radio 2.
You probably never give your kidneys a thought, but they’re hard at work for you 24 hours a day. They filter all the blood in your body 40 times a day through a million tiny filters and 140 miles of tubes. This lets them get rid of waste products and toxins, and balance the fluids and salts in your system. But keeping everything in your body in sync is hard work – in fact, your kidneys use ¼ of your energy.
How Much Fluid do I Need?
Keeping your fluid intake up is essential for healthy kidneys. About 20-30% of your fluid comes from foods (especially fruit and vegetables); the rest comes from fluids you drink.
As a very basic rule of thumb, women need about 1600mls a day from drinks and men about 2000mls a day. However, you’ll need more if you’re in a hot climate; if you’re doing a lot of exercise; if you have a fever; or if you’re pregnant (pregnant women need about 1900mls a day) or breastfeeding (you need 2200-2300mls a day).
When you’re on holiday, you’re likely to be out of your usual routine and probably won’t have a kettle to hand. You may also be distracted and busy with new activities – so it’s easy to forget that you need to drink as much as usual, and more if it’s hot, or you’re exercising. Even an air-conditioned environment can mean you speed up the rate at which you lose fluid, as sweat evaporates from your skin more quickly.
Are All Fluids the Same?
Water and non-alcoholic fluids all count towards your daily fluid intake. However, do bear in mind that sugary drinks contain a lot of calories, which can add up especially if you’re drinking more than usual.
You may have heard that caffeine-containing drinks make you lose water. In fact, this is only true if you drink a very large amount - coffee and tea up to about 400mg caffeine a day (that’s about 8 cups of tea, 4 mugs of instant coffee or 4 cups of brewed coffee) count towards your fluid intake.
Alcohol, on the other hand, is a diuretic – it makes you pee more. So drinking alcohol makes you prone to dehydration. Do bear this in mind if you’re tempted to drink more alcohol than usual when you’re on holiday.
How Do I Know if I’m Dehydrated?
Your body should be producing about 1.5 litres of urine a day. Of course, nobody expects you to measure this, but the colour of your urine is a good guide. If you’re dehydrated, your kidneys reabsorb more water, so your urine is more concentrated. You should aim to keep your urine pale straw-coloured – that means there’s enough fluid in your system.
The first things you’re likely to notice if you’re dehydrated are a dry, sticky mouth and feeling thirsty. Being dehydrated can also lead to tiredness and poor concentration, headaches, constipation and sometimes confusion. You’ll also be more prone to headaches and urinary tract infections. Not drinking enough fluids increases the risk of heat exhaustion and heat stroke, which is a medical emergency.
If you get dehydrated, common over-the-counter medicines like ibuprofen, along with lots of prescription medications, can damage your kidneys.
Dehydration and Pre-Existing Medical Conditions
Dehydration can have serious implications for individuals with pre-existing medical conditions, as it often exacerbates symptoms or triggers complications. For those with diabetes, for example, dehydration can lead to elevated blood sugar levels, making it harder to manage their condition effectively. Similarly, people with heart conditions are at increased risk, as dehydration can cause a drop in blood pressure, increased heart rate, and strain on the circulatory system.
Kidney conditions are particularly sensitive to dehydration, as insufficient fluids can impair kidney function or lead to kidney stones. For individuals with respiratory conditions like asthma or chronic obstructive pulmonary disease (COPD), dehydration can dry out airways, making it harder to breathe.
Even those with gastrointestinal disorders, such as irritable bowel syndrome (IBS), are likely to experience intensified symptoms when dehydrated. This is why staying properly hydrated is critical, especially for anyone managing health concerns. It helps maintain a stable internal balance and reduces the risk of avoidable medical emergencies.
How Safe is Drinking Water Abroad?
We take it for granted in the UK that tap water – whether for drinking, washing vegetables or brushing our teeth – is safe to drink. That’s also the case in most of Europe, the USA, Australia and New Zealand. But if you’re outside these regions, there’s a risk that the tap water may not have been treated to the same standards as in the UK.
Drinking contaminated water can leave you at risk of traveller’s diarrhoea – one of the quickest ways to ruin any holiday. But other conditions, including hepatitis A, typhoid and cholera can also be passed on through contaminated food and water.
What is Traveller’s Diarrhoea?
Traveller’s diarrhoea is a common and unpleasant condition that can strike while abroad. It usually happens after eating or drinking something contaminated with harmful bacteria, viruses or parasites.
Destinations with lower sanitation or hygiene standards tend to carry the highest risk. Typical symptoms include loose or watery stools, stomach cramps, nausea and sometimes fever. While it’s rarely serious, it can certainly put a damper on your holiday.
Managing Traveller’s Diarrhoea
If you do pick it up, the most important thing is to stay hydrated. Drink plenty of safe fluids and, if available, use oral rehydration solutions to replace lost salts and electrolytes.
Rest as much as you can, and stick to bland foods such as bananas, rice, applesauce and toast until your symptoms settle. See a doctor promptly if you develop a high fever, blood in your stools or signs of severe dehydration.
With a little care, traveller’s diarrhoea is often avoidable – and if it does happen, managing it well will usually mean you’re back on your feet and enjoying your trip before long.
Top Tips for Water Safety Abroad
When you’re travelling, the last thing you want is an upset stomach to spoil the fun. The good news is that with a few simple precautions, it’s easy to stay safe and still enjoy local food and drinks. Here are some handy tips to keep you feeling your best while you’re away.
Safe Drink Choices
Bottled drinks are generally the safest option while travelling – just make sure the seal is intact before opening. Hot drinks made with freshly boiled water are usually fine as well. One thing to be careful of is ice: even if your drink itself is safe, ice made from local tap water can undo your efforts to stay healthy.
Purifying Water
If bottled water isn’t available, purification methods are the next best option. Boiling water for at least one minute is one of the most reliable ways to make it safe, though this isn’t always practical on holiday. Purification tablets provide a quick alternative, but they can change the taste. Portable water filters are also widely available and can be very effective – just ensure you choose one specifically designed to remove bacteria and viruses from contaminated water. Standard domestic filters, such as those commonly used in the UK, won’t do the job.
Everyday Hygiene
Remember: if the local water supply isn’t safe to drink, it isn’t safe to brush your teeth with either. Keep a small supply of bottled or purified water in your bathroom to use when brushing, rinsing, or cleaning your mouth.
Food Safety
It’s not just what you drink that matters – some foods can also carry risks if they’ve been in contact with unsafe water. Be cautious with raw or undercooked seafood and shellfish, salads, and uncooked fruit or vegetables that may have been washed in contaminated water. Ice cream made from unpasteurised milk can also be a problem. Steer clear of foods sitting out on open buffets, which attract flies, and avoid street food unless it’s been freshly cooked and served piping hot. Unsealed bottles of mayonnaise are another thing best left untouched.
Looking after yourself on holiday doesn’t have to be complicated. By keeping an eye on what you drink, taking a few simple precautions with food, and remembering to stay hydrated, you’ll give yourself the best chance of feeling well throughout your trip. That way, you can spend less time worrying about water safety – and more time enjoying the experiences, sights and memories that make travel so special.
Before you head away on holiday, it’s also worth making sure you’ve got the right travel insurance in place. Even with the best precautions, illness can sometimes happen – and having cover gives you extra peace of mind that you’ll be looked after if you need medical help abroad. If you haven’t already arranged your policy, now is the perfect time to do so.