Have you ever stopped to read the label when standing in front of the water aisle at the supermarket? You've probably noticed a series of numbers, abbreviations, and technical terms that seem written in another language. Fixed residue, pH, sodium, calcium, magnesium... what do they really mean?

Learning to read a water label isn't as difficult as it seems. And once you know what to look for, you'll be able to choose the water that best suits your health needs, lifestyle, and daily habits.

Fixed residue: water's ID card

Fixed residue is the most important value to check. It tells you how many minerals are dissolved in one liter of water. It's measured in milligrams per liter (mg/l) and is determined by evaporating water at 180°C—what remains at the bottom are mineral salts.

Based on fixed residue, waters fall into four categories:

• Minimally mineralized: less than 50 mg/l—the lightest option, ideal for infants and those with kidney problems
• Low mineral (or slightly mineralized): between 50 and 500 mg/l—perfect for daily use, promotes diuresis
• Medium mineral: between 500 and 1500 mg/l—good for replenishing salts after exercise
• High mineral content: over 1500 mg/l—should be consumed in moderation and on medical advice

If you drink plenty of water throughout the day, a low-mineral water is your best choice. If you sweat a lot from work or sports, a medium-mineral water helps you recover the minerals you've lost.

pH: acidic or alkaline?

pH measures whether water is acidic, neutral, or alkaline. The scale ranges from 0 (very acidic) to 14 (very alkaline). Neutral pH is 7.

Most mineral waters have a pH between 6.5 and 8. This value shouldn't worry you too much—your body is perfectly capable of handling small variations in the acidity of the water you drink. Slightly alkaline waters (pH 7.5-8) can be more pleasant to the palate and may help with digestion.

The main minerals you should know about

Every water contains a unique mix of minerals. Here are the most important ones:

Calcium: important for bones and teeth. If you drink water with 300 mg/l of calcium and consume 2 liters a day, you're getting 600 mg of calcium—about 60% of your daily requirement. Waters rich in calcium (over 150 mg/l) are recommended if you don't eat dairy products or need to strengthen your bones.

Magnesium: essential for muscles and the nervous system. Waters with more than 50 mg/l are considered "magnesium-rich" and can help combat fatigue and muscle cramps.

Sodium: this is the mineral you should pay the most attention to. If you have high blood pressure, choose waters with less than 20 mg/l of sodium. The label "suitable for low-sodium diets" appears on waters with less than 20 mg/l.

Sulfates: stimulate digestion and liver function. Sulfate-rich waters (over 200 mg/l) can have a mild laxative effect.

Bicarbonate: aids digestion, especially after heavy meals. Bicarbonate-rich waters contain over 600 mg/l of bicarbonate.

Nitrites and nitrates: values to check

These are pollutants that can come from agricultural fertilizers. The law sets very strict limits: maximum 0.02 mg/l for nitrites and 10 mg/l for nitrates. Good water should have much lower values, ideally close to zero.

How to choose the right water for you

Every person has different needs. Here's a quick guide:

• Daily use: low-mineral water with fixed residue 100-300 mg/l
• Sports and sweating: medium-mineral water with magnesium and sodium
• Low-sodium diet: sodium under 20 mg/l
• Difficult digestion: bicarbonate over 600 mg/l
• Kidney stones: minimally mineralized, fixed residue under 50 mg/l
• Pregnancy: high calcium (over 300 mg/l) and low sodium

There's no perfect water for everyone. What matters is knowing how to read the label and making an informed choice based on your needs. Next time you buy water, take a few seconds to look at those numbers. You'll discover there's much more to that bottle than you imagined.

Take this guide with you next time you shop

When you're at the shelf, turn the bottle over and look for the label with the chemical analysis. It's usually on the back or side.

Check these three values in order:

First: look at the fixed residue. If it's between 50 and 500 mg/l, you've found water suitable for daily use. If it's under 50 mg/l, it's excellent for infants or those with kidney problems. If it's over 500 mg/l, it's fine for replenishing salts after sports, but not for everyday consumption.

Second: look for sodium. If you have high blood pressure, check that it's under 20 mg/l. You'll see "suitable for low-sodium diets" or "low sodium content" written on the label.

Third: if you need extra calcium (pregnancy, menopause, don't eat dairy), look for waters with calcium over 300 mg/l. You'll find it listed as "Ca++" or "Calcium".

Test it with the waters you have at home

Take three different bottles you've already bought. Put them on the table and compare the labels. You'll notice huge differences between brands. Some have 10 mg/l of sodium, others 50. Some have 20 mg/l of calcium, others 400.

This simple exercise will open your eyes—you've been drinking completely different waters without realizing it.

Create your own "water ID card"

Write on a small piece of paper:

• Main use (daily, sports, digestion)
• Any health concerns (high blood pressure, kidney stones, pregnancy)
• Preferences (sparkling, still, lightly sparkling)

Carry this note when you shop. It will help you remember what to look for on the label.

Change your water with the seasons

In summer, when you sweat more, switch to slightly more mineralized water. In winter, when you drink less, choose lighter water to promote diuresis.

Teach your children too

If you have children, involve them in choosing water. Make reading the label an educational game. Ask them to find the fixed residue, to read the calcium numbers. They'll grow up aware of what they're putting in their bodies.

Don't stick with famous brands

The most advertised waters aren't necessarily the best for you. Often lesser-known brands offer excellent quality water at lower prices. What matters is knowing how to read the label.

Keep a small water diary

For a week, note which water you drink and how you feel. Do you have more energy? Better digestion? Do you wake up fewer times at night to use the bathroom? Your body will give you the answers.

Learning to read water labels is a small gesture that can make a big difference for your health. Spend five minutes today understanding them, and tomorrow you'll always know what you're drinking.