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Donat Mg
Donat Mg from Rogaska Slatina, eastern Slovenia — 380 mg calcium, 1 000 mg magnesium, 1 500 mg sodium per litre. Hardness, what a litre contributes against the EFSA reference intakes, and the EU label claims the analysis supports.
Where it comes from
Donat Mg is the outlier of the whole category: about 1 000 mg of magnesium in a litre, roughly three times an adult daily reference intake, in a water whose total mineralisation is around 13 g per litre. Rogaska Slatina has sold it as a cure since the seventeenth century, and it is still labelled and dosed as a medicinal water — a measured glass on an empty stomach, not a bottle with lunch. Magnesium and sulphate together at these levels are a reliable osmotic laxative, which is the effect a large part of its market is buying.
Source: Rogaska Slatina, eastern Slovenia · Category: Natural mineral water sold as a medicinal water · Carbonation: Naturally carbonated
This is a reference table, not a diagnosis and not a prescription. If a clinician has put you on a sodium, calcium, potassium or fluid restriction, that number comes from them and overrides anything here. Analyses are revised as sources are re-tested, so the label on the bottle you are holding always outranks this page.
The published analysis
| Constituent | mg per litre | What a litre of it means |
|---|---|---|
| Calcium | 380 | 40% of the 950 mg calcium reference |
| Magnesium | 1 000 | 285.7% of the 350 mg magnesium adequate intake |
| Sodium | 1 500 | 75% of the 2.0 g sodium intake · 3.81 g as salt |
| Bicarbonate | 7 700 | |
| Sulphate | 2 200 | |
| Dry residue at 180 °C | 13 000 | the figure EU law uses for the mineral-content claims |
How hard it is
Hardness is nothing but the calcium and magnesium already in the table above, re-expressed as though all of it were calcium carbonate. For Donat Mg the arithmetic runs 380 ÷ 40.08 + 1 000 ÷ 24.31 = 50.63 mmol per litre.
| Unit | Value | Where you meet it |
|---|---|---|
| Millimoles per litre | 50.63 | the chemistry, and the German consumer bands |
| German degrees °dH | 283.9 | dishwasher and washing-machine settings in the Nordics and Baltics |
| French degrees °fH | 506.7 | French and Belgian labelling |
| mg per litre as CaCO₃ | 5 066.9 | the international classification and most water-utility reports |
That places it at very hard on the classification used in the international drinking-water literature, and hart (hard) on the three-band German scale printed on detergent packets. Hardness has no health-based guideline value; what it changes is limescale, soap and the taste. More on hardness.
What EU labelling law lets this water claim
Annex III of Directive 2009/54/EC fixes exactly which indications a natural mineral water may print and the figure each one requires. Applying those rules to the analysis above:
| Indication | Criterion | This water |
|---|---|---|
| “Very low mineral content” | not above 50 mg/l dry residue | does not qualify |
| “Low mineral content” | not above 500 mg/l dry residue | does not qualify |
| “Rich in mineral salts” | above 1 500 mg/l dry residue | qualifies |
| “Contains bicarbonate” | above 600 mg/l bicarbonate | qualifies |
| “Contains sulphate” | above 200 mg/l sulphate | qualifies |
| “Contains chloride” | above 200 mg/l chloride | no published figure |
| “Contains calcium” | above 150 mg/l calcium | qualifies |
| “Contains magnesium” | above 50 mg/l magnesium | qualifies |
| “Contains fluoride” | above 1 mg/l fluoride | no published figure |
| “Contains sodium” | above 200 mg/l sodium | qualifies |
| “Suitable for a low-sodium diet” | below 20 mg/l sodium | does not qualify |
A litre against a day
| Nutrient | Per litre | Share of an adult day |
|---|---|---|
| Calcium | 380 mg | 40% of the 950 mg EFSA reference intake |
| Magnesium | 1 000 mg | 285.7% of the 350 mg adequate intake for men |
| Sodium | 1 500 mg | 75% of the 2.0 g safe and adequate intake |
The sodium figure is the one to keep in view here: a litre is already a serious fraction of the day, and it arrives before bread, cheese or anything cured. That is a reason to treat this water as a drink you choose deliberately rather than the one that lives in the fridge.
Analyses: the figures each producer publishes on the label or in its technical sheet — see the basis line on every water page. Reference intakes: EFSA Dietary Reference Values. Label claims: Directive 2009/54/EC, Annex III. Mineral-water constituent limits and the fluoride labelling rule: Directive 2003/40/EC. Tap-water parametric values: Directive (EU) 2020/2184. Checked 2026-09-06.
Frequently asked questions
What is in Donat Mg?
Donat Mg is naturally carbonated from Rogaska Slatina, eastern Slovenia, natural mineral water sold as a medicinal water. The published analysis is 380 mg calcium, 1 000 mg magnesium, 1 500 mg sodium per litre.
Is Donat Mg hard water?
Calcium and magnesium together come to 50.63 mmol per litre, which is 283.9 °dH or about 5 066.9 mg per litre as calcium carbonate — very hard on the international scale and hart (hard) on the German one.
Is Donat Mg suitable for a low-sodium diet?
Not on the EU criterion, which reserves that claim for waters under 20 mg of sodium per litre. This one carries 1 500 mg per litre, so a litre is roughly 75% of the 2.0 g safe and adequate sodium intake before any food is counted.
How much magnesium does Donat Mg have?
1 000 mg per litre, which is about 285.7% of the EFSA adequate intake of 350 mg a day for adult men and 333.3% of the 300 mg figure for women. EU labelling allows a "contains magnesium" claim above 50 mg per litre.
Waters with a similar mineral load
Essentuki No. 17
Russia · Naturally carbonated
Essentuki No. 4
Russia · Naturally carbonated
Borjomi
Georgia · Naturally carbonated
Vichy Catalan
Spain · Naturally carbonated
All waters compared
The full table, grouped by mineral content.
Water hardness explained
Degrees, millimoles and parts per million, converted.
Know what you drank, not just what you bought
TempoLife logs hydration alongside food and sleep, so the litre you actually drank is in the same picture as everything else.