Magnesium Citrate, Anhydrous
Trimagnesium dicitrate — a high-magnesium citrate for supplements, pharmaceuticals and fortified foods
Magnesium citrate anhydrous (trimagnesium dicitrate) is the magnesium salt of citric acid with no water of crystallisation, supplying about 15–16% elemental magnesium. It is used as a well-absorbed magnesium source in tablets, capsules and powder blends. Each lot is tested against USP monograph parameters, including microbiological limits.
Also known as: Trimagnesium dicitrate anhydrous, trimagnesium citrate, tribasic magnesium citrate, E345(i).
🧪 Why Anhydrous Magnesium Citrate?
Magnesium citrate is sold in several forms that differ in magnesium content. The anhydrous form contains no water of crystallisation, so it delivers the most magnesium per gram. This keeps tablets and capsules smaller for the same dose. In the gut it dissolves into magnesium ions and citrate, and human studies show better absorption than magnesium oxide.
About 16% magnesium, versus about 12% for the nonahydrate
More bioavailable than magnesium oxide in human studies
Loss on drying ≤ 2.0% supports stable, accurate dosing
📊 Magnesium Content of Common Sources
| Magnesium source | Approx. Mg content | Note |
|---|---|---|
| Magnesium citrate, anhydrous (ASC-8065) | 15–16% | Highest Mg among the citrates |
| Magnesium citrate nonahydrate | ~12% | Less soluble than the anhydrous form |
| Magnesium bisglycinate | ~14% | Amino-acid chelate |
| Magnesium oxide | ~60% | High Mg, poorly soluble |
To supply 100 mg of magnesium, use about 650 mg of a lot assaying 15.4% Mg (100 ÷ 0.154).
📑 Regulatory Status
| Region | Status |
|---|---|
| Australia / NZ | Food uses are governed by the Food Standards Code (Schedules 15–17). Therapeutic goods use falls under TGA rules. Confirm the permitted use for your product category. |
| European Union | "Magnesium salts of citric acid" are permitted mineral forms (Directive 2002/46/EC; Regulation (EC) No 1925/2006). Trimagnesium dicitrate anhydrous is also food additive E345(i) in solid food supplements, up to 100,000 mg/kg (Regulation (EU) 2024/346). |
| Pharmacopoeias | Monographs in USP and Ph. Eur. |
| Upper intake levels | Supplemental magnesium: 350 mg/day for adults (NHMRC, Australia); 250 mg/day (EU) |
This raw material is not a finished therapeutic product. Customers are responsible for the regulatory status of their finished goods.
Strategic Selection
✅ Advantages
- ✓ Most magnesium per gram of the citrate forms
- ✓ Better absorbed than magnesium oxide
- ✓ Microbiologically tested for ingestible products
- ✓ Low moisture for stable blends
⚠️ Considerations
- ▲ Laxative effect at high doses
- ▲ Slightly hygroscopic: keep containers closed
- ▲ Lower Mg than oxide: larger dose mass
- ▲ Dose as elemental Mg, not salt weight
❓ Frequently Asked Questions
What is magnesium citrate anhydrous?
It is trimagnesium dicitrate, the magnesium salt of citric acid with no water of crystallisation. It contains about 15–16% magnesium, the highest magnesium content of the common magnesium citrates.
How much magnesium does 1 g supply?
About 145–164 mg of elemental magnesium, depending on the lot. Use the magnesium result on the COA to calculate your dose.
Is magnesium citrate better absorbed than magnesium oxide?
Human studies have found magnesium citrate to be more soluble and more bioavailable than magnesium oxide (Lindberg et al., 1990; Walker et al., 2003).
What is the difference between anhydrous and hydrated magnesium citrate?
The anhydrous form contains no water of crystallisation, so it has a higher magnesium content (about 16%) than the nonahydrate (about 12%). It is also more soluble in water than the hydrated forms.
Is there an upper limit for supplemental magnesium?
Yes. Australia's NHMRC sets an upper level of 350 mg/day for magnesium from supplements in adults. In Europe the limit is 250 mg/day. Above these levels, magnesium salts can cause a laxative effect.
🔬 Chemical Identity
📋 Specifications
📚 References
- United States Pharmacopeia. Magnesium Citrate monograph. USP–NF, current edition.
- Commission Regulation (EU) 2024/346 — authorisation and specifications of trimagnesium dicitrate anhydrous, E345(i).
- Directive 2002/46/EC, Annex II, and Regulation (EC) No 1925/2006, Annex II — permitted mineral substances.
- NHMRC. Nutrient Reference Values for Australia and New Zealand — Magnesium.
- Lindberg JS, Zobitz MM, Poindexter JR, Pak CYC. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr. 1990;9(1):48–55.
- Walker AF, Marakis G, Christie S, Byng M. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnes Res. 2003;16(3):183–191.
✅ Release Testing
Every lot is released against the specification in the Technical Data tab. This covers identity, magnesium assay, loss on drying, pH, impurity limits and microbiological limits. Each order ships with a lot-specific Certificate of Analysis showing the actual results, manufacture date and expiry date.
⚠️ GHS Classification (WHS Regulations, Australia)
Hazardous chemical. Not Dangerous Goods. Signal word: WARNING — GHS07 (exclamation mark).
- H315 Causes skin irritation.
- H319 Causes serious eye irritation.
- H335 May cause respiratory irritation.
Key precautions: avoid breathing dust (P261), wear gloves and eye protection (P280), and rinse eyes cautiously with water if contact occurs (P305+P351+P338).
These hazards apply to handling the bulk powder in the workplace. The full 16-section SDS is supplied with every order and is available on request.