Seven sneaky signs you’re dehydrated, even if you’re not thirsty. How much water should you drink?

Most of us assume just feeling thirsty means it’s time to drink. The trouble is, thirst is not an early warning system as many think, it actually tends to kick in once you have already lost around 1-2 per cent of your body’s water and by then your body may already be feeling the effects.

As we age that thirst signal also becomes weaker, so many older Australians are low on fluids without feeling thirsty at all. And in my clinical experience plenty of us simply aren’t drinking enough.

Australian women are advised to have about 2.1 litres of fluid a day and men about 2.6 litres, yet national survey data shows most of us fall short, particularly women and older adults.

My guideline for optimal hydration is 30ml per kg of your own body weight for optimal hydration. There are many telltale signs of dehydration which I am going to share with you.

The first, which is actually the simplest to check, is the colour of your urine. Pale coloured urine generally means you are well hydrated.

Dark yellow or amber means your kidneys are holding on to water because you need more.

The second is the afternoon slump. If you are fatigued by 3pm, it may not be your workload as you may think.

Research consistently shows that being dehydrated makes people feel more tired and less alert.

Before you reach for another coffee or a biscuit, try a big glass of water, and even better drink it outside to get some vitamin D and stay aligned with your circadian rhythms.

Third is brain fog and a short fuse. Dehydration affects how we feel as much as how we think.

Studies show that people who are even mildly dehydrated report more fatigue, tension, confusion and irritability, and find it harder to concentrate. If you’ve read the same email three times my advice is to go and have a tall glass of water.

The fourth sign is an annoying headache. In studies where people went without fluids for a day or more, many developed headaches. Water won’t cure every headache, but it is the first thing you should do.

Fifth is you feel dizzy when you stand up. Low fluids mean lower blood volume, so your blood pressure can dip when you get up quickly. That light-headed “head rush” is a common sign and in older people it can lead to falls.

The sixth sign is constipation. Your bowel draws water from food waste, and when you’re low on fluids it pulls out more, leaving stools hard and difficult to pass. This matters even more if you are increasing your fibre, which I always encourage. Fibre needs water to do its job, so as you add more fibre, drink more too.

Finally, there’s dry mouth and bad breath. Saliva is your mouth’s natural rinse. When you are dehydrated you make less of it, bacteria build up, and you’re left with a dry, sticky mouth and definitely less than fresh breath.

The good news is that hydration is an easy habit to build.

These are some of my tips to help you increase your water intake, starting with, keep a water bottle where you can see it.

Have a glass next to your kettle to remind you to drink your water. Add drinking to things you already do, such as a glass when you wake up and another with every meal.

Remember, too, that about a quarter of our fluid comes from food, so cucumber, watermelon, tomatoes, berries, soups and yoghurt all help. Milk, tea and coffee count as well, though plain water should be your main drink.

Also remember to drink more on hot days, when you exercise and when you are unwell.

If any of these signs persist even when you’re drinking well, see your GP, as they could possibly point to other health issues.

For me, personally, in the early days, I set an alarm on my phone to remind me to drink water, now it is second nature.

For most of us, though, the fix is really simple. Don’t wait for thirst or feeling parched.

Drink steadily through the day, and your energy, mood and gut will thank you.