Strontium: A Cautious Look at the Bone-Density Mineral
⚡ 60-Second Summary
Strontium is an alkaline-earth metal chemically similar to calcium. Two forms are sold: prescription strontium ranelate (Protelos/Osseor, marketed in Europe) which has fracture-endpoint RCT evidence — and OTC strontium citrate, which is dosed similarly but has no comparable trial base.
Important safety background: in 2014, regulators in the EU and elsewhere restricted strontium ranelate to severe osteoporosis without alternatives, after analyses linked it to myocardial infarction, venous thromboembolism, and DRESS skin reactions. The drug has since been withdrawn from major markets including the EU, Australia, and Canada.
OTC strontium citrate is still available in the US but is not FDA-approved for osteoporosis. Its safety profile relative to ranelate is debated. Discuss with your physician before using, especially if you have any cardiovascular history. Strontium also confounds DXA scan readings, falsely inflating BMD values.
What is strontium?
Strontium (chemical symbol Sr, atomic number 38) is an alkaline-earth metal in the same column of the periodic table as calcium (Ca) and barium (Ba). The body holds about 320 mg of strontium, almost all of it incorporated into bone in place of calcium. Trace dietary intake (1–5 mg/day) comes from grains, seafood, leafy greens, and drinking water — particularly hard water from limestone aquifers.
Mechanistically, strontium is a "dual-action" bone agent: it stimulates osteoblast bone formation and inhibits osteoclast bone resorption — at least in cell-culture and animal studies. The clinical correlate is increased BMD on DXA, but how much of that BMD increase is real new bone vs. pure substitution of strontium for calcium (a denser atom) is contested.
Strontium should not be confused with the radioactive isotope ⁹⁰Sr, a fission product that accumulates in bone and is associated with leukemia. Supplemental strontium is the stable, non-radioactive isotope.
Evidence and the regulatory story
1. Strontium ranelate (the prescription drug)
Two large pivotal trials drove the original 2004 EU approval:
- SOTI (2004) — 1,649 postmenopausal women with osteoporosis, 2 g/day strontium ranelate vs placebo for 3 years. 41% reduction in vertebral fracture risk.
- TROPOS (2005) — 5,091 women, 5-year extension. Significant reductions in vertebral and (in high-risk subgroups) hip fractures.
On these results, strontium ranelate was widely prescribed in Europe through the 2000s.
2. The 2013–2014 safety re-evaluation
Pooled trial and post-marketing data revealed:
- Increased risk of myocardial infarction (~60% relative increase vs placebo, low absolute event rate)
- Increased risk of venous thromboembolism
- Reports of DRESS syndrome (Drug Reaction with Eosinophilia and Systemic Symptoms), a potentially fatal hypersensitivity reaction
The European Medicines Agency restricted use to severe osteoporosis without alternatives in 2014, then progressively limited prescribing. The manufacturer withdrew the product from the EU and other major markets in 2017–2018 due to commercial reasons; it remains available in some countries.
3. Strontium citrate (the OTC form)
Strontium citrate has not been tested in adequately powered fracture-endpoint trials. Open-label and small RCTs in osteopenic women suggest similar BMD-raising effects to ranelate at equivalent elemental doses (~680 mg elemental Sr/day), but cardiovascular safety in this OTC population is largely unstudied. By chemical analogy, the cardiovascular concerns of ranelate plausibly extend to citrate, though this is unresolved.
The DXA-scan confounding problem
This is a critical and frequently-overlooked issue. Strontium has a higher atomic number than calcium (38 vs 20), so it absorbs more X-ray energy at any concentration. When strontium incorporates into bone matrix, DXA — which works by measuring X-ray attenuation — reports an inflated areal BMD value.
Estimates suggest strontium ranelate BMD gains in trials are ~50% real new bone and ~50% pure radio-density artifact. Adjustment formulas have been proposed but no single one is universally accepted. Patients who supplement strontium and undergo DXA monitoring should ensure their clinician is aware — otherwise apparent BMD "gains" may overstate true fracture-risk reduction.
Forms compared (ranelate vs citrate)
| Form | Best for | Typical elemental dose | Notes |
|---|---|---|---|
| Strontium ranelate (Rx) | Severe osteoporosis without alternatives (where still available) | 2 g salt = 680 mg elemental Sr/day | Withdrawn in EU/AU/CA. Cardiovascular and DRESS warnings. Requires specialist supervision. |
| Strontium citrate (OTC) | Used by some integrative practitioners; not FDA-approved | ~680 mg elemental Sr/day (one capsule typically 227 mg) | No fracture-endpoint trials. Cardiovascular safety largely unstudied. Same DXA confounding issue. |
| Strontium carbonate (Rx, niche) | Pediatric ¹³⁹Sr radiotherapy formulations (very rare) | Not for daily use | Pharmaceutical use only. |
| Strontium lactate, gluconate | Older European supplement forms | Variable | Less common. Same caveats as citrate. |
Dosing and administration
- Dietary intake: 1–5 mg/day (no RDA — not classified as essential)
- OTC supplement dose (commonly used): 680 mg elemental strontium/day
- Important administration tip: strontium and calcium compete for absorption. Take strontium at bedtime, separated from calcium, dairy, and food by at least 2 hours.
- Co-administration with adequate calcium and vitamin D — required to ensure strontium does not displace calcium from bone matrix.
Safety, side effects, and contraindications
Cardiovascular and thromboembolic risk
Pooled data on strontium ranelate showed increased rates of MI and VTE. The same risk for strontium citrate is plausible by chemical analogy, even if not formally established in OTC populations. Avoid strontium if you have any of:
- History of myocardial infarction or unstable angina
- Ischemic heart disease, peripheral arterial disease, cerebrovascular disease
- Uncontrolled hypertension
- Personal or family history of venous thromboembolism
- Prolonged immobilization
DRESS syndrome and severe skin reactions
Onset typically 3–6 weeks after starting; presents with fever, rash, eosinophilia, and multi-organ involvement. Stop strontium immediately if any rash develops in the first 2 months and seek urgent medical care.
Common (less serious) side effects
- Nausea, diarrhea (usually transient)
- Headache, eczema
- Memory disturbance, seizures (rare)
Pregnancy, breastfeeding, kidney disease
Avoid in pregnancy, breastfeeding, and severe renal impairment.
Drug and nutrient interactions
- Calcium — competes for absorption. Separate by at least 2 hours.
- Tetracycline and quinolone antibiotics — strontium binds them and reduces absorption; separate by 2–4 hours.
- Bisphosphonates — generally not co-administered; clinical guidance varies.
- Antacids (Mg/Al hydroxide) — reduce strontium absorption.
- Hormone replacement therapy — no direct interaction, but combined risk of VTE.
Who might benefit — and who shouldn't bother
| Possibly appropriate (with physician) | Should avoid strontium |
|---|---|
| Severe postmenopausal osteoporosis intolerant of bisphosphonates and denosumab | Anyone with cardiovascular history (MI, IHD, PAD, CVA) |
| Patients failing first-line therapy with high fracture risk | Anyone with prior or family history of VTE |
| Adults working with a knowledgeable bone specialist who can interpret DXA | Pregnant or breastfeeding women |
| — | Anyone with severe kidney disease |
Frequently asked questions
Is strontium safe for bone health?
Strontium ranelate has well-documented cardiovascular and skin-reaction risks and was withdrawn from major markets. OTC strontium citrate has not been tested in fracture-endpoint trials and the cardiovascular safety is unsettled. Use only after physician discussion.
What is the difference between strontium ranelate and strontium citrate?
Ranelate is the prescription form with fracture-reduction RCT evidence (SOTI, TROPOS). Citrate is the OTC form delivering similar elemental strontium but without a comparable trial base.
How does strontium affect DXA scan readings?
Strontium has a higher atomic number than calcium and inflates DXA-measured BMD values. Estimates suggest about half the apparent BMD gain in trials reflects real new bone; the rest is radio-density artifact. Tell your clinician you are taking strontium before any DXA scan.
Who should not take strontium?
Anyone with cardiovascular history, prior VTE, prolonged immobility, severe kidney disease, pregnancy, or breastfeeding. The 2014 EU restriction lists explicit cardiovascular exclusions.
Can I take strontium with calcium?
Take them at different times of day (e.g., calcium with breakfast and lunch, strontium at bedtime) — they compete for absorption. Adequate calcium and vitamin D are still required for strontium to be safe and effective.
Why is strontium still sold OTC if there are concerns?
In the US, strontium citrate is regulated as a dietary supplement, not a drug. The FDA has not formally evaluated its bone-health claims. Many integrative clinicians still use it, but the evidence base is weaker than its marketing suggests.
Related ingredients and articles
Ranelate vs Citrate
The careful comparison of prescription and OTC forms.
Best Bone Supplements (2026)
How calcium, vitamin D, K2, magnesium, and boron actually fit together.
Calcium
The structural mineral strontium displaces. Always required when supplementing strontium.
Vitamin K2 (MK-7)
The cofactor that directs calcium into bone instead of arteries.
Disclaimer: This information is for educational purposes only and should not replace medical advice. Always consult a qualified healthcare provider before starting any supplement, especially if you have a medical condition, are pregnant, or take prescription medications. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.