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Microcrystalline Hydroxyapatite (Ossein-Hydroxyapatite Compound)
A calcium source made from bovine bone, supplying calcium and phosphorus as hydroxyapatite together with collagen and other bone matrix proteins.
What the evidence says
Hydroxyapatite (MCHC) doesn't have enough studies with structured effect-size data yet to pool a verdict. Browse the studies below for individual findings.
Most evidence is from medium-quality meta-analyses and randomised trials published 1985–2026 with a typical study size of 62 participants.
Based on 17 studies · 1 meta-analysis · 10 RCTs · 1,860 total participants
Confidence
High confidenceBy outcome
One 2009 meta-analysis of six trials found bone density held up 1.02% better with ossein-hydroxyapatite compound than with calcium carbonate (95% CI 0.63-1.41), and a 3-year cohort of 851 women points the same way. But the comparator in almost every trial is another calcium salt, the trials are small and mostly open-label, several authors recur across the trials and the meta-analysis, and no study measured fracture. The one double-blind placebo-controlled trial found no significant bone density change at 6 months, and in an independent randomised trial bone turnover fell by similar amounts as with ordinary calcium (no between-group difference is reported in the abstract). It is a calcium source with a small surrogate edge over carbonate, not a proven bone-protecting agent in its own right.
11 randomised trials
100% were about Hydroxyapatite (MCHC) in an audit of 11 of them
Every randomised or controlled trial of Hydroxyapatite (MCHC) indexed in PubMed, not a hand-picked subset. Meta-analyses and systematic reviews are deliberately excluded from this count: most of them cover many compounds at once, so counting them would inflate it.
PubMed · as of Oct 2026
Microcrystalline hydroxyapatite compound, also called ossein-hydroxyapatite compound or complex, is made from bovine bone.
It supplies calcium and phosphorus in the crystal form bone itself uses, together with the organic bone matrix (ossein): type I collagen and non-collagenous proteins and peptides, including small amounts of growth factors.
It is taken as a calcium source for bone health, and in some countries it is licensed as a medicine for preventing bone loss. Most trials compare it with calcium carbonate rather than with placebo.
A 2009 meta-analysis of six such trials found bone density held up about 1% better with the hydroxyapatite compound, and later open-label and observational studies point the same way.
The trials are small, mostly unblinded and largely from one research network, they measure bone density rather than fractures, and the one double-blind placebo-controlled trial found no significant change in bone density at 6 months.
In an independent trial bone turnover fell by similar amounts with it and with ordinary calcium (no between-group difference is reported in the abstract), while blood calcium rose less, and in a randomised comparison of five calcium salts it lowered parathyroid hormone significantly less than the others.
Because the active is calcium, the same upper limits, drug spacing rules and kidney cautions apply as for any calcium supplement.
Supplies calcium together with phosphorus in the hydroxyapatite crystal form that makes up bone mineral. In one trial it raised serum phosphate and the calcium-phosphate product, which conventional calcium salts did not.
In a randomised trial in postmenopausal women, a dose of microcrystalline hydroxyapatite raised ionised calcium less than the same calcium dose as citrate or carbonate, while bone turnover fell by similar amounts (no between-group difference is reported in the abstract).
All calcium sources lower parathyroid hormone acutely, which reduces the drive to resorb bone. In a randomised comparison of five calcium salts in healthy men, the ossein-hydroxyapatite compound lowered parathyroid hormone significantly less than calcium carbonate or citrate, and less than the other two salts tested, though still more than an inactive vehicle. A 2-year controlled trial in corticosteroid-treated patients reported biochemistry "suggestive of a reduction in parathyroid over-activity".
The ossein fraction contains type I collagen and non-collagenous proteins, including small amounts of IGF-I, IGF-II, TGF-beta and osteocalcin. Trial authors suggest this explains results beyond the calcium dose, but that these proteins act on bone after being swallowed has not been shown in humans.
The population most studied. Trials show slightly better bone density maintenance than calcium carbonate, with no fracture data. Usually combined with adequate vitamin D.
Calcium itself is appropriate in pregnancy, but this bone-derived form has one trial of 20 heparin-treated women. Prefer a conventional calcium salt unless a clinician advises otherwise.
Not studied in lactation. A conventional calcium salt is the better-characterised choice.
Use only under medical supervision. It supplies both calcium and phosphate, and raised the calcium-phosphate product in one trial.
Not suitable. It is made from bovine bone. Calcium citrate or carbonate supply the same mineral.
Small older trials studied it to limit drug-induced bone loss, with partly non-significant results. Bone protection in these groups should be managed by a clinician.
Calcium reduces bisphosphonate absorption. Take the bisphosphonate first on an empty stomach and separate calcium by at least 30-60 minutes.
Calcium binds levothyroxine in the gut and reduces its absorption. Separate by at least 4 hours.
Calcium chelates tetracyclines and reduces their absorption. Separate by 2-3 hours.
Calcium reduces fluoroquinolone absorption. Take the fluoroquinolone at least 2 hours before or 6 hours after calcium.
Calcium inhibits non-heme iron absorption. Separate supplemental calcium and iron by at least 2 hours.
Thiazides reduce urinary calcium loss, so added calcium can raise blood calcium. Monitor serum calcium.
Loop diuretics increase urinary calcium excretion, potentially increasing calcium requirements.
Long-term corticosteroid use decreases intestinal calcium absorption and increases urinary excretion. Higher calcium intake may be needed.
Raised blood calcium increases the risk of digoxin toxicity and arrhythmia. Calcium supplementation in people on digoxin should be monitored.
Chronic use increases vitamin D catabolism, reducing calcium absorption. Increased calcium and vitamin D may be needed.
Tip: Split the dose, increase fluids and fibre
Tip: Take with meals
Tip: Stay hydrated and keep total calcium within the upper limit
Tip: Count calcium from all supplements and food against the upper limit
Tip: Avoid with a beef or bovine protein allergy
Hydroxyapatite (MCHC) has an evidence score of 4.5/10 — emerging evidence based on 17 indexed studies, including 1 meta-analysis. A calcium source made from bovine bone, supplying calcium and phosphorus as hydroxyapatite together with collagen and other bone matrix proteins. Representative study: PMID 19407667.
The commonly studied dose of Hydroxyapatite (MCHC) is 3,320 mg of the compound daily, as two 830 mg tablets twice a day (about 712 mg elemental calcium), the regimen of the 3-year osteoporosis trial and the 851-woman cohort. A 6-month pain trial used 1,660 mg a day. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
The best time to take Hydroxyapatite (MCHC) is in split doses through the day. Take it with food. Trials gave the compound twice daily.
Hydroxyapatite (MCHC) has a moderate safety rating: most adults tolerate it at the studied doses, but there are precautions worth knowing. Reported side effects include kidney stones (calcium-containing), allergic reaction in people sensitive to bovine proteins, constipation. How often they occur is not established for all of them. Use caution if any of these apply to you: Hypercalcaemia (raised blood calcium); Hypercalciuria or a history of calcium kidney stones without medical supervision; Severe kidney impairment, where both the calcium and the phosphate it supplies can accumulate.
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Reviewed by Dr. Baher Al Hakim · Last reviewed October 2026 · evidence from 17 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.