For years I drank somewhere between two and four litres of water a day, and I felt quietly pleased with myself for it. More water, better health — that's the rule, isn't it? Then I started paying closer attention to how I actually felt, and I realised I had never once stopped to ask where that rule came from.
What I found surprised me. So let's talk honestly about how much water you should drink — the good, the not-so-good, and the part nobody mentions.
Where did the "two litres a day" rule come from?
I went looking for the evidence behind the two-litre target, and I couldn't find a solid scientific basis for it. It appears to be one of those numbers that has been repeated so often, in so many places, that it now feels like established fact. It isn't. It's closer to a rough rule of thumb that escaped into the wild.
That matters, because fluid needs genuinely vary from person to person. Your body size, your climate, how much you sweat, what you eat, your medications and any health conditions all shift the number. In my clinical practice I've worked with people who drink comparatively little water and show no signs of dehydration whatsoever — and others who clearly need much more. A single figure printed on a water bottle can't account for any of that.
What changed when I drank less
My own experience was the thing that made me curious in the first place. When I was drinking the most water, I was also dealing with higher blood pressure, circulation that didn't feel great, and digestion that felt sluggish. I've since brought my intake down to under a litre on most days, and I feel considerably better for it.
I want to be straight with you about what that is and isn't. It's one person's experience, not a study, and I changed my diet around the same time — so I can't honestly isolate water as the single cause. But it was enough to stop me treating a number as a target and start treating my body as the better source of information.
Water, stomach acid and digestion
Here's a mechanism worth understanding. Your stomach is meant to be acidic. That acidity does two important jobs: it helps break down protein, and it acts as a barrier against microbes you'd rather not have setting up residence further down the digestive tract.
When you flood your stomach with a large volume of water right around a meal, you dilute that acid and nudge the pH upward. For some people that can mean protein isn't broken down as efficiently, and the barrier function is a little less robust. It's not a reason to fear water — it's a reason to think about timing. I now sip between meals rather than washing dinner down with two big glasses, and my digestion is happier for it.
Your diet changes how much water you need
This is the piece that genuinely shifted my thinking. When your body burns fat for fuel, it produces water as a by-product — what's known as metabolic water. The more metabolically flexible you become at burning fat, the more water you generate internally.
Since I reduced refined carbohydrates and increased healthy fats, my thirst has dropped noticeably. Even during exercise I need less fluid than I used to. There's a related point here that's worth taking seriously: constant, unquenchable thirst can be a sign of blood sugar dysregulation. If you're always parched, the better question may not be "am I drinking enough?" but "what's going on with my blood sugar?" — and that's a conversation to have with your GP rather than something to solve with a bigger bottle.
Quality matters as much as quantity
If you are drinking water, make it good water. Unfiltered tap water carries a range of things you'd rather not accumulate, and a decent filter is one of the simplest health investments you can make. I'd far rather someone drink a litre of well-filtered water than three litres of whatever comes out of the tap.
There's also an emerging area of research I find genuinely interesting, around deuterium — a heavier form of hydrogen present in water and food — and whether a build-up affects how efficiently our mitochondria produce energy. I'll be upfront: this is an early and contested field, not settled science, and I'd encourage you to treat it as a question researchers are exploring rather than a conclusion to act on.
So how much water should you drink?
My honest answer is: let your thirst lead, and drink slowly rather than in big gulps. Have a sip, wait a little, and notice whether the thirst has actually settled. Urine colour is a useful rough gauge too — pale straw is generally a good sign.
And then the important caveat, because this is health advice and you deserve the full picture. Drinking to thirst suits most healthy adults, but it isn't universal. If you're exercising hard, working in heat, unwell with a fever, pregnant, older (thirst signals blunt with age), prone to kidney stones or urinary infections, or taking medications that affect fluid balance, your needs may be genuinely higher. Please don't dramatically cut your fluid intake on the strength of a blog post — talk to your doctor, especially if you have a kidney, heart or blood pressure condition.
Key takeaways
- The two-litre rule isn't as evidence-based as it sounds — treat it as a rough guide, not a prescription.
- Use thirst as your primary signal, sip rather than gulp, and check urine colour as a simple backup gauge.
- Drink between meals rather than large volumes with food, to protect stomach acid and digestion.
- Reducing refined carbohydrates and eating more healthy fats increases the metabolic water your body makes, which often reduces thirst.
- Constant thirst deserves investigation — it can signal blood sugar issues. See your GP.
- Filter your water. Quality matters at least as much as quantity.
- Higher needs apply in heat, illness, pregnancy, older age and some medical conditions — check with your doctor before making big changes.
This is exactly the kind of question I love working through with clients at me&my wellness, because it illustrates something bigger: health rarely comes from following a generic number. It comes from understanding your own body, your own diet and your own circumstances, and then adjusting with curiosity rather than rules. How much water you should drink isn't a fixed answer — it's a conversation between you and your body, and the good news is that your body is a better communicator than you might think.
Want to go deeper on this? Book a free 30-minute discovery call with Anthony at meandmywellness.com.au