In short: In human studies, magnesium aspartate and lactate were absorbed markedly better than magnesium oxide. Carbonate, pidolate, lactate and gluconate are common magnesium forms approved in the EU for food supplements. Carbonate provides a lot of magnesium per gram and dissolves in stomach acid. Orotate and aspartate are mainly found in pharmacy medicines.
Key points
- Four forms are on the EU list: carbonate, pidolate, lactate and gluconate may be added to food supplements.
- Good absorption confirmed: in a US study, lactate and aspartate were absorbed equally well, and markedly better than oxide.
- A lot or a little powder: carbonate contains around 25 to 29% magnesium, gluconate only just over 5%. For 250 mg of magnesium, you need 0.9 g or 4.6 g respectively.
- Orotate: the EU food safety authority EFSA could not confirm its safety as a food supplement, because of orotic acid.
- Aspartate: well absorbed, and found mainly in pharmacy preparations. Keep a gap between it and your thyroid tablet.
Contents
- What other forms of magnesium are there besides citrate and glycinate?
- The six forms compared
- What is magnesium carbonate good for?
- Magnesium orotate: what does the EFSA say?
- What is magnesium pidolate good for?
- Magnesium lactate: how well is it absorbed?
- Magnesium aspartate: what's the debate about?
- Magnesium gluconate: more powder needed, good results in an animal study
- Which of these forms suits you?
- Frequently asked questions
- Limits of the research and all sources
What other forms of magnesium are there besides citrate and glycinate?
Beyond the well-known forms, there's a second line-up you'll come across on packaging, in effervescent tablets and on medicine leaflets: carbonate, orotate, pidolate, lactate, aspartate and gluconate. They all deliver the same magnesium. What differs is what it's bound to, how much magnesium is packed into each gram, and how well each form dissolves.
This article introduces these six forms one by one. If you first want to know which form is the best overall choice, read our overview Which magnesium is best? We also have dedicated articles on the most common forms: magnesium citrate, magnesium glycinate, magnesium L-threonate and magnesium malate.
What the studies show: A systematic review of 14 comparative studies found that organic forms are, on average, absorbed better than inorganic ones. All forms maintained a normal magnesium level in healthy people.1 A review paper stresses that the amount per serving and your own magnesium status often matter more than the salt itself.2
The six forms compared
The table gives you all six forms at a glance. We calculated the magnesium content from the molar masses.3 Solubility data comes from the European Pharmacopoeia and the EFSA assessment.4, 6
| Form | Magnesium content (our calculation) | Powder for 250 mg magnesium | Solubility in water | Absorption in studies | EU list for food supplements5 | Typical use |
|---|---|---|---|---|---|---|
| Magnesium carbonate (inorganic) | 28.8% (pure); commercial 24–27% | 0.9–1.0 g | practically insoluble, dissolves in acid | no rise in blood in one effervescent-tablet study9 | yes | Effervescent tablets, heartburn remedies |
| Magnesium orotate (organic) | 6.6% (dihydrate) | 3.8 g | sparingly soluble | no human comparison studies | no | Medicines |
| Magnesium pidolate (organic) | 8.7% | 2.9 g | very readily soluble | more magnesium in urine/blood over months14, 15 | yes | Drinking ampoules |
| Magnesium lactate (organic) | 10.2% (dihydrate) | 2.5 g | slightly soluble | as good as chloride and aspartate, better than oxide7 | yes | Tablets, including sustained-release |
| Magnesium aspartate (organic) | 7.5% (dihydrate) | 3.3 g | readily soluble | as good as lactate, better than oxide7, 20 | no | Pharmacy medicines |
| Magnesium gluconate (organic) | 5.4% (dihydrate) | 4.6 g | readily soluble | best of ten forms in rats8 | yes | Tablets, powder |
How we calculate this: Magnesium weighs 24.3 units. The whole compound weighs, for example, 280.5 units for pidolate and 450.6 units for gluconate with bound water.3 So: 24.3 ÷ 280.5 = 8.7% and 24.3 ÷ 450.6 = 5.4%. For 250 mg of magnesium, divide 250 by the percentage: 250 ÷ 0.087 ≈ 2.9 g of pidolate.
Many of these salts contain bound water, which lowers the percentage. We state the form described in the pharmacopoeia. Commercial carbonate is a hydrous, "basic" carbonate with 40 to 45% magnesium oxide, which works out to 24 to 27% magnesium.4
What is magnesium carbonate good for?
Magnesium carbonate is an economical form: it contains a lot of magnesium per gram, so a small amount of powder covers a day's portion. You'll often find it in effervescent tablets. As white "magnesia", you might know it from gymnastics or climbing.
Carbonate barely dissolves in water but dissolves well in acid.4 In the stomach, it reacts with stomach acid, producing dissolved magnesium, water and a little carbon dioxide. Heartburn remedies that contain magnesium carbonate rely on exactly this reaction: they neutralise stomach acid.11 That's why it's best to take carbonate with a meal, when your stomach is producing acid anyway. You can read how stomach acid and acid-reducing tablets affect absorption in How is magnesium absorbed by the body?
What the studies show: In an animal study with ten magnesium forms, all were absorbed at between 50 and 67%, with organic forms slightly ahead of inorganic ones like carbonate.8 In a lab study with intestinal cells, even more magnesium passed through the cell layer from carbonate, pidolate and oxide than from citrate, chloride and sulphate.10
Magnesium orotate: what does the EFSA say?
Magnesium orotate is magnesium bound to orotic acid. Orotic acid is a precursor in the body's build-up of genetic material and occurs naturally, mainly in milk: cow's milk contains 20 to 100 mg per litre.6 Orotate has a low magnesium content of around 6.6% and is sparingly soluble in water.6
If you search for magnesium orotate, you mostly find medicines. The studies were done with these too. As an ingredient for food supplements, magnesium orotate is not approved in the EU.5, 6
What the studies show: Researchers studied 79 people with severe heart failure who received either magnesium orotate or a placebo for a year, alongside their regular medication. After one year, 75.7% of the orotate group were still alive, versus 51.6% in the placebo group.12 The dose was high: 6,000 mg in the first month, then 3,000 mg a day. In a small study of 20 men, 3,000 mg of orotate a day did not change sperm quality.13
Important: The EFSA has assessed magnesium orotate twice, in 2009 and 2025. The reason for its concerns is orotic acid: in animal studies, it promoted the growth of liver tumours that had been triggered by other substances. In 2009, the EFSA considered the intended amounts a cause for concern. In 2025, it could not confirm the safety of magnesium orotate as a novel food.6 For context: 250 mg of magnesium as orotate brings with it around 3.2 g of orotic acid (our calculation from the molar masses). If magnesium orotate has been prescribed to you, take it as discussed with your doctor. For everyday food supplementation, you're better off with a form from the EU list.
What is magnesium pidolate good for?
Magnesium pidolate is a very readily soluble form, well suited to drinking ampoules and drinks.4 The magnesium is bound to pidolic acid, also known as pyroglutamic acid, a ring-shaped variant of the amino acid glutamic acid. Pidolate contains 8.7% magnesium and is on the EU list for food supplements.4, 5 It's especially common in Italy, where it's searched for far more often than in Germany (our keyword data).
What the studies show: In a six-month study of 14 people with high blood pressure, 365 mg of magnesium a day as pidolate raised urinary magnesium from 5.3 to 7.7 mmol a day, a sign that more magnesium was being absorbed.14 In kidney transplant patients with low magnesium levels, pidolate raised the blood value after six months.15 A review paper sees signs of good cellular uptake; it was funded by the manufacturer of a pidolate product.16
Magnesium lactate: how well is it absorbed?
Well: in a comparative study, lactate performed on a par with chloride and aspartate, and clearly ahead of oxide.7 Lactate is the magnesium salt of lactic acid, which also forms in yoghurt and sauerkraut. As a dihydrate it contains 10.2% magnesium and is on the EU list.3, 5 It dissolves poorly in water.4 Lactate is also available as a tablet that releases magnesium slowly.19
What the studies show: In the US study, lactate, chloride and aspartate were absorbed equally well; only around 4% of oxide made it through.7 In a study of 30 young men, urinary magnesium rose after a month of 292 mg of magnesium a day as lactate.18 A slow-release lactate tablet was absorbed at around 38%, compared with magnesium given intravenously, as measured via urine.19
Magnesium aspartate: what's the debate about?
Magnesium aspartate is well absorbed: in studies, more magnesium from it reached the body than from oxide.7, 20 The magnesium is bound to aspartic acid, an amino acid found in every protein and one your body also makes itself.21 Aspartate is not on the EU list for food supplements.5 You'll therefore find it mainly in pharmacy preparations sold as medicines.
Aspartate is debated for one reason: aspartic acid also acts as an excitatory messenger in the brain. Online, this sometimes gets turned into the claim that aspartate is a bad idea in the evening or is hard on the nerves. We haven't found studies that show this for magnesium aspartate specifically. A review paper describes aspartic acid as a normal building block of metabolism and notes that the effects of very high intakes still need more research.21 For context: 250 mg of magnesium as aspartate provides around 2.7 g of aspartic acid (our calculation).
What the studies show: In a German study of healthy people, participants taking aspartate excreted more magnesium in their urine than those taking oxide, a sign of better absorption.20 In a study of 15 healthy people, magnesium aspartate reduced the absorption of thyroid hormone by 12%, citrate by 7%.22
Magnesium gluconate: more powder needed, good results in an animal study
Gluconate dissolves readily in water, which makes it a good fit for powders you mix into a drink.4 It's the magnesium salt of gluconic acid, which is derived from glucose, and it's on the EU list.5 The catch is the low percentage: at 5.4% magnesium, you need around 4.6 g of powder for 250 mg, which means several large tablets.
What the studies show: In an animal study with ten magnesium forms, gluconate was absorbed best of all. Organic forms such as gluconate, lactate and aspartate also stayed in the body longer than inorganic ones.8 We haven't found human comparison studies for gluconate.
Which of these forms suits you?
For a food supplement, lactate, pidolate, carbonate and gluconate are all solid choices: they're on the EU list and among the forms your body can make good use of. The table below helps you choose based on your situation.
| If you … | obvious choice | why |
|---|---|---|
| want to swallow fewer tablets | carbonate | lots of magnesium per gram3, 4 |
| prefer to drink your magnesium | pidolate or gluconate | dissolve very well in water4 |
| want a form with human comparison data | lactate | absorbed as well as chloride, better than oxide7 |
| take acid-reducing tablets | lactate, pidolate or gluconate | carbonate needs stomach acid to dissolve4, 11 |
| have a preparation from your doctor | the one prescribed | orotate and aspartate are mainly sold as medicines |
All forms deliver the same magnesium, so the officially approved health claims apply to every one of them:
- Magnesium contributes to a reduction of tiredness and fatigue.
- Magnesium contributes to normal muscle function.
- Magnesium contributes to normal energy-yielding metabolism.
- Magnesium contributes to normal functioning of the nervous system.
- Magnesium contributes to electrolyte balance.
You'll find everything magnesium does in the body in our article Magnesium: what it does in the body.
Our take: Of the six forms, lactate is the best studied in humans and a good choice if tablets suit you well. Pidolate and gluconate are practical if you'd rather drink your magnesium. Carbonate is the most economical form and works well with a meal. Across all of them, the same rule applies: take your daily amount regularly, and split larger amounts across two meals, because smaller portions are absorbed proportionally better.25 Which of these forms comes out ahead in the long run is something direct human comparison studies still need to show.
Important: Adults shouldn't take more than 250 mg of magnesium a day from food supplements, unless a doctor advises otherwise.23 If your kidney function is reduced, magnesium can build up in the body, regardless of the form.24 Talk to your doctor first in that case. You need a gap of a few hours from thyroid hormone22, certain antibiotics and osteoporosis medicines. You'll find the details in When should you take magnesium?
Frequently asked questions
What is magnesium carbonate good for? For an economical magnesium supply with little powder, often as an effervescent tablet. Magnesium contributes to normal muscle function. Magnesium contributes to a reduction of tiredness and fatigue. Because carbonate neutralises stomach acid, it's also used in larger amounts in heartburn remedies.11
Does magnesium carbonate help with constipation? Magnesium that isn't absorbed in the gut draws in water. In larger amounts, every magnesium form softens stools; in one study, bowel movements with oxide and aspartate were 1.8 to 3.2 times more frequent at very high amounts.20 If constipation persists, get it checked out by a doctor. More on this in Too much magnesium.
Is magnesium carbonate harmful? Not in normal amounts. It's on the EU list of magnesium compounds for food supplements.5 As with every form, the upper limit of 250 mg of magnesium a day from supplements applies.23 With kidney disease, only after talking to your doctor.24
What is magnesium orotate good for? Orotate delivers magnesium bound to orotic acid. Studies exist mainly with medicines, for example in people with severe heart failure.12 As a food supplement, the EFSA has not confirmed its safety.6 For everyday supplementation, you're better off with a form from the EU list.
What is magnesium orotate dihydrate? The usual commercial form: magnesium orotate with two bound water molecules. It contains around 6.5% magnesium.6 So 1,000 mg of it provides about 65 mg of magnesium.
Does magnesium pidolate or magnesium carbonate help you lose weight? We haven't found studies examining either of these forms for weight loss. Magnesium contributes to normal energy-yielding metabolism. That applies to every form.
Limits of the research and all sources
For the six forms in this article, there are only a few human comparison studies. Most are small, last days to weeks, and measure magnesium in blood or urine, not your supply over months. For gluconate, the comparison data comes from an animal study; for carbonate and pidolate, partly from lab studies with intestinal cells.8, 10 Lab findings don't always agree: in one cell study, carbonate and pidolate did well, while in another, bone cells absorbed less magnesium from pidolate than from other salts.10, 17
There are also conflicting findings in humans. In 61 young women, blood magnesium did not rise after ten days of carbonate effervescent tablets, but it did with oxide.9 In kidney transplant patients, pidolate had not measurably raised the blood value after 15 days; a newer competing form worked faster.15 In the pidolate study in people with high blood pressure, blood pressure did not fall more than with placebo.14 The study on the lactate tablet came from the manufacturer.19 The heart study with orotate was small, ran at a single centre and has not been repeated.12 We found no studies, positive or negative, on how aspartate affects sleep or the nerves.
Show all 25 sources
| # | Study | Who was studied | Result | Strength of evidence |
|---|---|---|---|---|
| 1 | Pardo et al. 2021, Nutrition | 14 comparative studies | organic forms better than inorganic, share falls with amount; all forms maintain levels in healthy people | systematic review |
| 2 | Schuchardt & Hahn 2017, Curr Nutr Food Sci | review of absorption | salt form less important than thought; amount and supply status more decisive | review paper |
| 3 | PubChem: Carbonate 11029, Orotate dihydrate 90479692, Pidolate 18601084, Lactate dihydrate 71587589, Aspartate dihydrate 76968352, Gluconate dihydrate 71587201, Orotic acid 967 | chemical database | molar masses as basis for our percentage calculation | reference data |
| 4 | European Pharmacopoeia 7.0, monographs Magnesium carbonate, Magnesium lactate dihydrate, Magnesium pidolate, Magnesium aspartate dihydrate, Magnesium gluconate | pharmacopoeia | solubility; carbonate 40–45% as MgO, practically insoluble, dissolves in acid; pidolate 8.49–8.84% Mg | reference data |
| 5 | Directive 2002/46/EC, Annex II (amended by Regulation 1170/2009) | EU law | list of approved magnesium compounds: including carbonate, gluconate, lactate, L-pidolate; not: orotate, aspartate | legal basis |
| 6 | EFSA NDA Panel 2025, EFSA Journal | assessment of magnesium orotate dihydrate | safety not confirmed; 2009: NOAEL orotic acid 50 mg/kg, margin to intended amounts inadequate; around 6.5% Mg; cow's milk 20–100 mg orotic acid/l | official assessment |
| 7 | Firoz & Graber 2001, Magnes Res | healthy people, around 250 mg Mg/day, 4 preparations | oxide around 4% absorption; chloride, lactate, aspartate equally good and better | small study |
| 8 | Coudray et al. 2005, Magnes Res | 80 rats, 10 forms | absorption 50–67%; gluconate highest; organic salts stay in the body longer | animal study |
| 9 | Ivanovic et al. 2022, BioMetals | 61 young women, 10 days | oxide best; carbonate effervescent tablets without a rise | small study |
| 10 | Kyselovič et al. 2021, Physiol Res | intestinal cells in the lab, 7 salts | carbonate, pidolate, oxide passed through better than citrate, chloride, sulphate | cell study |
| 11 | Maton & Burton 1999, Drugs | review of antacids | carbonates and magnesium salts neutralise stomach acid | review paper |
| 12 | Stepura & Martynow 2009, Int J Cardiol | 79 people with severe heart failure, orotate 6,000/3,000 mg, 1 year | survival 75.7% vs 51.6% with placebo | small controlled study, single centre, funding not stated |
| 13 | Závaczki et al. 2003, Magnes Res | 20 men, 3,000 mg orotate, 90 days | no change in sperm quality | small controlled pilot study |
| 14 | Ferrara et al. 2008, Cardiology | 14 people with high blood pressure, 15 mmol pidolate, 6 months | urinary magnesium 5.3 → 7.7 mmol/day; blood pressure as with placebo | small controlled study |
| 15 | Stefanelli et al. 2023, J Clin Med | 43 kidney transplant patients, 370 mg Mg/day | pidolate: no measurable rise after 15 days, rise after 6 months; competing form faster | comparative study without randomisation, no outside funding |
| 16 | Maier et al. 2020, Nutrients | review of headache and magnesium | pidolate possibly well absorbed and cell-permeable | review paper, funded by Sanofi (manufacturer of a pidolate product) |
| 17 | Farruggia et al. 2014, Magnes Res | human cell lines, 3 salts | pidolate less available in bone-like cells | cell study |
| 18 | Wary et al. 1999, Br J Clin Pharmacol | 30 young men, 12 mmol lactate, 1 month | urinary magnesium rose, otherwise no change | controlled study |
| 19 | Dogterom et al. 2018, Drug Dev Ind Pharm | healthy people, lactate sustained-release tablet vs infusion | absorption around 20% (blood) or 38% (urine) fasting | small study, authors at the manufacturer |
| 20 | Mühlbauer et al. 1991, Eur J Clin Pharmacol | 24 healthy people, aspartate vs oxide preparations | more urinary magnesium with aspartate; bowel movements 1.8 to 3.2 times more frequent at high amounts | small study with commercial preparations |
| 21 | Holeček 2023, Nutrients | review of aspartic acid | protein building block, metabolism, messenger; effects of high intake still open | review paper |
| 22 | Attinger et al. 2025, Clin Transl Sci | 15 healthy people | aspartate reduced absorption of levothyroxine by 12%, citrate by 7% (not significant) | controlled study |
| 23 | EFSA / SCF 2001 | official opinion | upper limit 250 mg/day from supplements | official assessment |
| 24 | Rosner et al. 2023, Mayo Clin Proc | review paper | build-up with reduced kidney function | review |
| 25 | Fine et al. 1991, J Clin Invest | healthy people, increasing amounts with a meal | absorbed share falls from 65% to 11% | controlled measurement study |
Author: PRONESIUM Editorial Team · Last reviewed: 01/10/2026 · This article does not replace medical advice.
