Strontium Toxicity: What the Evidence Shows

Table of Contents

1. What the Evidence Actually Says
2. Strontium Ranelate: Heart Attack & Clotting Risk
3. Bone Effects of Excess Strontium
4. Why Strontium Behaves the Way It Does
5. Who, If Anyone, Is at Risk
6. Radioactive Strontium-90 Is a Different Topic
7. What the Evidence Means in Practice
8. Warning Signs in People Taking High-Dose Strontium
9. Key Research Papers
10. Connections
11. Featured Videos

What the Evidence Actually Says

Most pages about a mineral “toxicity” describe a recognized poisoning syndrome — a set of symptoms, a blood threshold, an antidote. Stable strontium does not fit that mold, and it is worth being candid about that from the start. There is no established human poisoning syndrome from the strontium found in ordinary food and water. Strontium is not an essential nutrient, there is no recommended intake and no “deficiency” to correct, and there is also no official nutritional Tolerable Upper Intake Level (UL) for it — not because it is known to be limitlessly safe, but because it has never been treated as a nutrient that people need to dose at all.

So where do the genuine concerns come from? Almost entirely from large, pharmaceutical-sized doses, not from diet. It helps to keep three very different things separate:

• Dietary strontium — the few milligrams a day most people absorb from water and plant foods. This is harmless at normal intakes; the body handles it much as it handles a little extra calcium. No toxicity here.
• Strontium ranelate — a prescription osteoporosis medicine that delivered roughly 680 mg of elemental strontium a day, on the order of 200 times a typical dietary intake. This is where the only well-documented human harms appear: increased cardiovascular events and blood clots, plus a rare severe drug reaction. It was never approved in the United States, was restricted in Europe in 2013–2014, was reported as effectively discontinued around 2017, and lost its European authorisation in 2020 at the maker’s request for commercial reasons; a 2021 review says it is available again as a generic medicine.
• Over-the-counter strontium supplements — usually strontium citrate, sold for “bone support,” delivering hundreds of milligrams of elemental strontium. These have not been studied for safety the way the drug was, so their cardiovascular and bone-mineralization safety is genuinely unresolved rather than proven safe.

And then, completely apart from all of the above, there is strontium-90, the radioactive isotope. Its hazard is ionizing radiation, not chemical toxicity, and it does not belong in the same conversation. It is addressed in its own section below only to prevent the very common confusion between “strontium” the bone mineral and “strontium-90” the fallout product.

The honest summary, then: a person eating a normal diet has effectively nothing to worry about from strontium. The questions worth taking seriously apply only to people swallowing large supplemental or pharmaceutical doses — and for them, the concern is real.

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Strontium Ranelate: Heart Attack & Clotting Risk

The single most important safety story about strontium is the rise and fall of strontium ranelate, because it is the one setting where high-dose strontium was given to large numbers of people and watched carefully. Understanding it tells you almost everything that is known about strontium’s human harms.

The drug arrived with real promise. Two large randomized controlled trials — SOTI (Meunier and colleagues, 2004) and TROPOS (Reginster and colleagues, 2005) — showed that 2 grams a day of strontium ranelate reduced the risk of new spine fractures in postmenopausal women with osteoporosis (SOTI: 49% in the first year and 41% over three years; TROPOS: 39%), and reduced non-vertebral fractures (TROPOS: 16%), with a 36% reduction in hip fractures in a high-risk subgroup. On that strength it was approved in the European Union in 2004. (For the disease it was meant to treat, see Osteoporosis.)

Then the post-marketing safety picture darkened. As the drug was used more widely and pooled analyses accumulated, the regulator’s pooled trial data showed an excess of cardiovascular events — especially myocardial infarction (heart attack) — in people taking strontium ranelate compared with placebo, though the data sets do not all agree. A Danish registry study of 3,252 users (Abrahamsen and colleagues, 2014) found that many already had conditions now contraindicated: ischaemic heart, peripheral vascular or cerebrovascular disease in 19.2% of women and 29.5% of men. After adjustment, heart attack risk was not significantly increased (women: hazard ratio 1.05, 95% confidence interval 0.79–1.41; men: 1.28, 0.74–2.20), stroke was borderline (women: 1.23, 0.98–1.55; men: 1.64, 0.99–2.70), and deaths from any cause were higher than in users of other osteoporosis drugs (women: 1.20, 1.10–1.30; men: 1.22, 1.03–1.45). A UK primary-care study of 112,445 treated women found no increase in heart attack or cardiovascular death (Cooper and colleagues, 2014). A 2021 review accepts the increased risk of clots and says the heart attack signal “has been detected in some studies” but “is not supported by wider analyses” (Curtis and colleagues, 2021); two of its three authors declare fees from several drug companies, including the drug’s maker. Two other harms rounded out the picture:

• Venous thromboembolism (VTE) — blood clots forming in the deep veins of the legs (deep-vein thrombosis) that can break loose and travel to the lungs (pulmonary embolism). The ranelate trials showed a higher rate of these clots than placebo, which is why a personal history of clotting became a reason not to use the drug.
• DRESS syndrome — drug rash with eosinophilia and systemic symptoms, a rare but potentially life-threatening hypersensitivity reaction with a widespread rash, fever, and internal-organ involvement, reported in patients on strontium ranelate (Cacoub and colleagues, 2013). It typically appears within the first weeks of treatment. That review confirmed 47 cases up to March 2011, with a median of 33.5 days to the skin reaction, a death rate of 8.5%, and at most 1 case in 24,112 newly treated people in France.

The regulatory response was decisive. In 2013–2014 the European Medicines Agency (EMA) sharply restricted strontium ranelate: it was confined to severe osteoporosis in people who could not take other treatments, contraindicated in anyone with a history of heart disease, stroke, peripheral arterial disease, uncontrolled high blood pressure, or clotting disorders, and made subject to regular cardiovascular monitoring. Commercially, the manufacturer is reported to have effectively discontinued it around 2017, and on 14 April 2020 the European Commission withdrew its authorisation at the maker’s request, for commercial reasons (EMA). A 2021 review says it is now available again as a generic medicine (Curtis and colleagues, 2021). Its place in therapy became narrow under those restrictions. An earlier UK health-technology assessment had found it clinically effective but less cost-effective than the bisphosphonate alendronate, and said the evidence needed strengthening, particularly for hip fractures (Stevenson and colleagues, 2007).

The European Medicines Agency reported its pooled figures from around 7,500 women: heart attack in 1.7% on the drug versus 1.1% on placebo (relative risk 1.6, 95% confidence interval 1.07–2.38), and clots in 1.9% versus 1.3% (relative risk 1.5, 1.04–2.19). It concluded that the risk could be managed by limiting use to people with no history of heart and circulatory problems who cannot take other osteoporosis medicines. A 2014 review compared regulatory files with published papers: the heart attack data appeared in no primary publication, and clot data in only 5 of 9. Its authors concluded that “the risks of strontium use are similar to the benefits” (Bolland and Grey, 2014).

Two honest caveats keep this in proportion. First, the absolute increase in cardiovascular events per person was modest, and some analyses argued the signal was driven partly by who was prescribed the drug; the regulators nonetheless judged the risk unacceptable for routine use given the alternatives. Second, and crucially for readers, this evidence is about the ranelate salt at 2 g/day — it does not automatically transfer to the much-less-studied over-the-counter strontium citrate, but it also does not exonerate it. The element delivered is the same, the doses are in the same hundreds-of-milligrams range, and no large safety trial has cleared citrate of the cardiovascular question. Whether the drug’s risks apply to citrate is not known.

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Bone Effects of Excess Strontium

Strontium’s defining quirk is that the body treats it as a calcium look-alike. It sits one row below calcium in the periodic table, carries the same charge, and is handled by many of the same transport systems — so wherever calcium goes, a little strontium tends to follow, and that is overwhelmingly into bone. At ordinary dietary levels this substitution is trivial and harmless. At the high doses used in supplements and the former drug, two distinct bone-related effects matter, and they pull in opposite directions.

1. The DXA “bone density” artifact — bones look stronger than they are. Bone density is usually measured by dual-energy X-ray absorptiometry (DXA), a scan that infers density from how much X-ray the bone absorbs. Strontium has a far higher atomic number than calcium (38 versus 20) and blocks X-rays much more strongly per atom. When strontium replaces some calcium in bone, the bone absorbs more X-ray and the DXA machine reports a falsely high density. Analyses of the ranelate trials concluded that a large share of the headline “bone-density increase” was this measurement artifact rather than real new bone (Blake and Fogelman, 2005). The Cochrane review put numbers on this: the pooled gain in lumbar spine density over two years was 11.29 before adjusting for strontium content and 5.44 after (weighted mean differences; O’Donnell and colleagues, 2006). A rising DXA number on strontium is partly an illusion, and a scan alone does not prove that strontium has strengthened a skeleton.

2. Impaired mineralization at very high or sustained exposure. Building healthy bone depends on calcium and phosphate crystallizing correctly into the bone matrix. When strontium substitutes for too much calcium, this hardening step can go wrong. At high exposures, strontium can cause a mineralization defect — bone that contains the right scaffolding but is incompletely or abnormally mineralized, a picture related to osteomalacia (“soft bones”). This has been documented mainly in extreme settings: animal studies, very high intakes, and historically in children with very high strontium exposure relative to calcium. The U.S. Agency for Toxic Substances and Disease Registry (ATSDR) states that the most consistent effects of excess oral strontium are rickets and osteomalacia, especially in the young. It is not something a normal diet produces, but it is the biological reason that “more strontium” is not safely “more bone.” Pors Nielsen’s review of strontium’s biological role (2004) lays out how the calcium-substitution behaviour underlies both the potential benefit and this dose-dependent hazard.

There is also a simple interaction worth knowing: because strontium and calcium compete for the same absorption pathway, large strontium doses can blunt calcium absorption, and adequate calcium can blunt strontium absorption. This is one reason strontium products and calcium were taken at different times in the drug’s dosing instructions, and one reason strontium is never a substitute for getting enough calcium and vitamin D (see Calcium and Vitamin K2, which helps direct calcium into bone rather than arteries).

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Why Strontium Behaves the Way It Does

Why is there no everyday strontium toxicity, yet real concern at high doses? The answer comes down to the calcium-mimicry idea taken to its logical conclusion.

Picture calcium handling as a well-run postal system: the gut absorbs it, the blood ships it, and the skeleton is the warehouse where most of it is stored. Strontium is like a slightly oversized parcel that fits the same trucks and the same warehouse shelves. In small numbers, a few of these parcels mixed in with the calcium cause no trouble at all — the system barely notices, and the kidneys clear the surplus. That is the situation with a normal diet, and it is why strontium has no nutritional upper limit for food. A health-based value does exist: ATSDR derived a minimal risk level of 2.0 mg/kg/day for oral exposure to stable strontium lasting 15–364 days.

The trouble starts only when you flood the system with parcels — the hundreds of milligrams in a supplement or the former drug. Now strontium accumulates in the bone warehouse in meaningful amounts, where two things follow from its physical differences from calcium. Because each strontium atom is heavier and blocks more X-ray, the warehouse looks fuller on a DXA scan than it really is (the density artifact). And because strontium does not crystallize into bone mineral exactly the way calcium does, packing too much of it in can make the stored bone lower quality (the mineralization defect). Meanwhile, the cardiovascular signal seen with the drug is a separate, less fully explained effect of sustained high-dose exposure — the reason regulators treated it as a drug-safety problem rather than a nutrient question.

This is also why strontium has no “deficiency” counterpart in any meaningful clinical sense: the body has no requirement for it, no dedicated role for it, and no shortage to correct. It enters health conversations almost solely through osteoporosis and supplements — never through nutritional need. (The companion Strontium Deficiency hub explains why a true deficiency syndrome does not exist.)

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Who, If Anyone, Is at Risk

Because dietary strontium is harmless, “at risk” really means at risk from high-dose strontium products. The people for whom strontium is genuinely a concern are a narrow, identifiable group:

• Anyone who took, or is considering, strontium ranelate (where still available outside the U.S.) — especially with any history of heart attack, angina, stroke, peripheral arterial disease, uncontrolled high blood pressure, or blood clots. For these people the drug is contraindicated; the regulator judged the cardiovascular and clotting risks too high for them. (See Arrhythmia and the broader cardiology section for related heart concerns.)
• People taking high-dose over-the-counter strontium citrate for bones, particularly those with cardiovascular risk factors. The safety of these products has not been established by the kind of large trials done for the drug, and no large trial has tested whether the drug’s cautions apply to them.
• People with significant kidney impairment, who clear strontium less efficiently and can accumulate more of it at high supplemental doses (see Kidney Disease). Among 100 people on hemodialysis who had bone biopsies, bone strontium levels and strontium/calcium ratios were higher in those with osteomalacia (soft bones) than in those with other types of kidney bone disease. This is an association, bone aluminum rose alongside strontium in that group, and the authors call for further studies of strontium’s role (D’Haese and colleagues, 2000).
• Anyone relying on DXA scans while taking strontium — not a health danger in itself, but a real risk of being misled by an artificially high bone-density reading into thinking treatment is working better than it is.
• Industrial or environmental exposure — high occupational exposure to strontium compounds is uncommon and regulated; it is not a typical consumer concern.

Notice who is not on this list: people simply eating a normal diet, or drinking ordinary tap or mineral water. Strontium content varies several-fold between regions because of differing soil and water, but even the higher end of natural intake is orders of magnitude below pharmaceutical doses and is not a recognized hazard.

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Radioactive Strontium-90 Is a Different Topic

It is worth stating plainly because the confusion is so common: strontium-90 (Sr-90) is not what this page is about, and it is not the same kind of hazard. Everything above concerns stable strontium, where any concern is chemical (calcium-mimicry, mineralization, the cardiovascular drug signal). Strontium-90 is a radioactive isotope, and its danger is entirely ionizing radiation.

Sr-90 is produced by nuclear fission — it was spread globally by atmospheric weapons testing in the mid-20th century and is released in nuclear-reactor accidents. The reason it is feared is precisely the calcium-mimicry described above: because the body treats strontium like calcium, inhaled or swallowed Sr-90 is deposited in bone and bone marrow, where it stays for years (its radioactive half-life is about 29 years) and its radiation can damage the marrow that makes blood cells. That radiation exposure is what raises the long-term risk of leukemia and bone cancer — a radiation effect, not a chemical-poisoning effect. Famously, Sr-90 measured in children’s baby teeth helped document fallout exposure and contributed to the case for the 1963 atmospheric test-ban treaty.

The contrast is the whole point: the stable strontium in your diet, your water, and even in strontium supplements is not radioactive and emits no ionizing radiation. Taking a strontium supplement does not expose you to Sr-90. Authoritative profiles of radioactive strontium and its health effects are maintained by public-health agencies (for example, the U.S. Agency for Toxic Substances and Disease Registry). Because that radiological topic is governed by radiation safety rather than nutrition, it is mentioned here only to draw the line clearly — you can see how the site treats genuinely toxic, bioaccumulating metals on the Toxic Minerals & Heavy Metals hub.

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What the Evidence Means in Practice

The practical picture is low-key, because for most people there is genuinely nothing to fix. A few points cover almost every real-world situation:

• Strontium in food or water is not a recognized problem. There is no recognized dietary strontium toxicity, so testing for it, restricting it, or “detoxing” it would be effort spent on a non-problem.
• High-dose strontium supplements are marketed as a “safe, natural” alternative, and no large trial has tested that. The benefit evidence for over-the-counter strontium citrate is weak (no large fracture-outcome trials), and the safety questions raised by the prescription drug — cardiovascular events, clotting, and bone-mineral quality — have never been resolved for the supplement.
• The European Medicines Agency contraindicates the drug in people with ischaemic heart disease, peripheral arterial disease, cerebrovascular disease or uncontrolled hypertension, and no trial has tested whether high-dose supplements carry the same risk for them. This is the group the regulators were most worried about.
• The best-established bone basics lie elsewhere. The well-established foundations are adequate calcium and vitamin D, vitamin K2, enough protein, and regular weight-bearing and resistance exercise — plus, for diagnosed osteoporosis, medicines with strong evidence and approval such as bisphosphonates and denosumab. Strontium, at best, is a debated add-on, not a cornerstone.
• Strontium skews bone-density scans, so a DXA result in someone taking strontium reads falsely high unless the artifact is taken into account. Routine bloodwork such as the Comprehensive Metabolic Panel, which checks calcium and kidney function.

In short: dietary strontium is not a recognized hazard, the safety of supplemental strontium is unresolved, and the bone-health basics above are the ones with the evidence behind them.

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Warning Signs in People Taking High-Dose Strontium

Because there is no everyday strontium-poisoning syndrome, the red flags here apply specifically to people taking high-dose strontium products (the former drug or over-the-counter strontium). In anyone taking such a product, hospitals treat the following as urgent signs:

• Chest pain, pressure, or tightness; shortness of breath; or pain spreading to the arm or jaw — possible signs of a heart attack, which hospitals treat as an emergency.
• Swelling, pain, redness, or warmth in one leg (often the calf) — a possible deep-vein clot — or sudden breathlessness, chest pain on breathing in, or coughing up blood, which can signal a clot that has traveled to the lungs. This is an emergency.
• A spreading skin rash with fever, facial swelling, or feeling generally very unwell, especially within the first few weeks of starting strontium — the pattern of the serious DRESS reaction, which hospitals treat as urgent. The published review of these cases says a rash on the drug “should lead to prompt and permanent treatment discontinuation” (Cacoub and colleagues, 2013).
• Sudden weakness or numbness on one side, trouble speaking, or facial droop — signs of a stroke, which hospitals treat as an emergency.

Outside of those acute situations, the numbers for the drug are these: heart attack in 1.7% versus 1.1% on placebo and clots in 1.9% versus 1.3% in the regulator’s pooled data, set against a fracture benefit that one 2014 review judged similar in size to those risks. The sources on this page give no such numbers for high-dose over-the-counter strontium. Strontium in ordinary food or water is not a recognized reason for medical care.

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Key Research Papers

1. Meunier PJ, Roux C, Seeman E, et al. (2004). The effects of strontium ranelate on the risk of vertebral fracture in women with postmenopausal osteoporosis (SOTI). New England Journal of Medicine;350(5):459-468. — DOI: 10.1056/NEJMoa022436. — doi:10.1056/NEJMoa022436
2. Reginster JY, Seeman E, De Vernejoul MC, et al. (2005). Strontium ranelate reduces the risk of nonvertebral fractures in postmenopausal women with osteoporosis (TROPOS). The Journal of Clinical Endocrinology & Metabolism;90(5):2816-2822. — DOI: 10.1210/jc.2004-1774. — doi:10.1210/jc.2004-1774
3. Reginster JY, Bruyère O, Sawicki A, et al. (2009). Long-term treatment of postmenopausal osteoporosis with strontium ranelate: results at 8 years. Bone;45(6):1059-1064. — DOI: 10.1016/j.bone.2009.08.004. — doi:10.1016/j.bone.2009.08.004
4. O'Donnell S, Cranney A, Wells GA, et al. (2006). Strontium ranelate for preventing and treating postmenopausal osteoporosis. Cochrane Database of Systematic Reviews;(3):CD005326. — DOI: 10.1002/14651858.CD005326.pub2. — doi:10.1002/14651858.CD005326.pub2
5. Abrahamsen B, Grove EL, Vestergaard P (2014). Nationwide registry-based analysis of cardiovascular risk factors and adverse outcomes in patients treated with strontium ranelate. Osteoporosis International;25(2):757-762. — DOI: 10.1007/s00198-013-2469-4. — doi:10.1007/s00198-013-2469-4
6. Cacoub P, Descamps V, Meyer O, et al. (2013). Drug rash with eosinophilia and systemic symptoms (DRESS) in patients receiving strontium ranelate. Osteoporosis International;24(5):1751-1757. — DOI: 10.1007/s00198-013-2265-1. — doi:10.1007/s00198-013-2265-1
7. Blake GM, Fogelman I (2005). Long-term effect of strontium ranelate treatment on bone mineral density. Journal of Bone and Mineral Research;20(11):1901-1904. — DOI: 10.1359/jbmr.050810. — doi:10.1359/jbmr.050810
8. Marie PJ (2006). Strontium ranelate: a physiological approach for optimizing bone formation and resorption. Bone;38(2 Suppl 1):S10-S14. — DOI: 10.1016/j.bone.2005.07.029. — doi:10.1016/j.bone.2005.07.029
9. Pors Nielsen S (2004). The biological role of strontium. Bone;35(3):583-588. — DOI: 10.1016/j.bone.2004.04.026. — doi:10.1016/j.bone.2004.04.026
10. Stevenson M, Davis S, Lloyd-Jones M, et al. (2007). The clinical effectiveness and cost-effectiveness of strontium ranelate for the prevention of osteoporotic fragility fractures in postmenopausal women. Health Technology Assessment;11(4):1-134. — DOI: 10.3310/hta11040. — doi:10.3310/hta11040
11. European Medicines Agency (2014). Strontium ranelate: recommendation to restrict use following review of cardiovascular safety. — EMA — strontium ranelate referral
12. European Medicines Agency. Strontium ranelate: marketing authorisation withdrawn 14 April 2020 at the holder’s request, for commercial reasons. — EMA — strontium ranelate product page
13. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Strontium (including strontium-90). — ATSDR — Strontium Toxicological Profile
14. Cooper C, Fox KM, Borer JS (2014). Ischaemic cardiac events and use of strontium ranelate in postmenopausal osteoporosis: a nested case-control study in the CPRD. Osteoporosis International;25(2):737-745. — DOI: 10.1007/s00198-013-2582-4. — doi:10.1007/s00198-013-2582-4
15. Curtis EM, Cooper C, Harvey NC (2021). Cardiovascular safety of calcium, magnesium and strontium: what does the evidence say? Aging Clinical and Experimental Research;33(3):479-494. — DOI: 10.1007/s40520-021-01799-x. — doi:10.1007/s40520-021-01799-x
16. Bolland MJ, Grey A (2014). A comparison of adverse event and fracture efficacy data for strontium ranelate in regulatory documents and the publication record. BMJ Open;4(10):e005787. — DOI: 10.1136/bmjopen-2014-005787. — doi:10.1136/bmjopen-2014-005787
17. D’Haese PC, Schrooten I, Goodman WG, et al. (2000). Increased bone strontium levels in hemodialysis patients with osteomalacia. Kidney International;57(3):1107-1114. — DOI: 10.1046/j.1523-1755.2000.00938.x. — doi:10.1046/j.1523-1755.2000.00938.x

PubMed Topic Searches

1. PubMed: Strontium ranelate, cardiovascular events, and heart attack
2. PubMed: Strontium ranelate, venous thromboembolism, and safety
3. PubMed: Strontium, bone mineralization, and osteomalacia
4. PubMed: Strontium and the DXA bone-density artifact
5. PubMed: Strontium-90, bone, and radiation health effects

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Connections

• All Minerals
• Strontium Overview
• Strontium Deficiency Hub
• Calcium
• Magnesium
• Vitamin K2 (Menaquinone)
• Osteoporosis
• Arrhythmia
• Kidney Disease
• Toxic Minerals & Heavy Metals
• Comprehensive Metabolic Panel

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