Strontium citrate is a dietary supplement that combines the mineral strontium with citric acid, sold over the counter primarily for bone health. It is not an FDA-approved medication. In the United States and Canada, it’s classified as a dietary supplement, placing it in a different regulatory category than prescription osteoporosis drugs. Most people searching for it have heard it may help with bone density and want to understand what it actually does, how it compares to the prescription form of strontium, and whether it’s safe.
How Strontium Citrate Works in Bone
Strontium is a naturally occurring mineral that’s chemically similar to calcium. Your bones can’t easily tell the two apart, so when you take strontium, a small percentage of it gets incorporated into bone tissue in place of calcium. This substitution appears to have a dual effect: it may slow the breakdown of old bone while encouraging the formation of new bone. That combination is unusual, since most osteoporosis treatments do one or the other.
The citrate portion of strontium citrate is simply the delivery vehicle. Citric acid is a common organic acid (the same one found in citrus fruits) that binds to the strontium and helps it dissolve in your digestive system for absorption.
Strontium Citrate vs. Strontium Ranelate
The most studied form of strontium is strontium ranelate, a prescription drug used in Europe and other countries for severe osteoporosis. It has never been approved in the United States. Strontium citrate, by contrast, is the form you’ll find on supplement shelves in North America.
The key question is whether the citrate form delivers strontium to bone as effectively as the ranelate form. A study in rats compared the two head-to-head, measuring how much strontium actually ended up in bone tissue. Rats given strontium citrate had significantly higher bone strontium levels than those given strontium ranelate. However, after adjusting for slight differences in the elemental strontium dose each group received, the researchers concluded that strontium ranelate and citrate appear similarly effective at delivering strontium to bone. In other words, what matters is the strontium itself, not the molecule it’s attached to.
Evidence for Bone Density Benefits
Here’s the honest picture: there are no large-scale human clinical trials on strontium citrate specifically. The major trials that showed bone density improvements and reduced fracture risk all used strontium ranelate at prescription doses. So the evidence for strontium citrate in humans is limited to case reports and extrapolation from ranelate data.
One published case series followed three patients with osteoporosis who took over-the-counter strontium citrate for several years. The results were notable. One patient saw total hip bone mineral density increase by 9.2% over six years. Another experienced a 12% increase at the hip and 6.5% at the lumbar spine over five years. A third showed a 10.7% increase at the spine in two years. The authors noted these improvements were similar in magnitude to what’s been reported with prescription strontium ranelate.
Three patients is far from proof, and there’s an important caveat about how bone density is measured when strontium is involved (more on that below). But these cases do suggest the citrate form has biological activity in human bone.
The DXA Scan Problem
Strontium creates a real measurement problem. When strontium replaces some calcium in bone, it absorbs X-rays more strongly than calcium does. This means DXA scans, the standard test for bone density, will overestimate your actual bone mineral density if you’ve been taking strontium. The overestimation isn’t trivial. Depending on the DXA machine used, every 1% of calcium replaced by strontium in bone can inflate the reading by roughly 9 to 11%.
This matters for two reasons. First, some of the bone density “improvement” seen in strontium users on DXA scans is an artifact of the measurement, not real bone growth. Researchers estimate that about half the apparent gain is real and half is due to this X-ray effect. Second, if you stop taking strontium, your future DXA scans will need correction factors to be interpreted accurately, since strontium leaves bone slowly over time. If you’re taking strontium citrate and getting DXA scans, your doctor should know about it.
Cardiovascular Safety Concerns
The biggest safety question around strontium comes from the prescription ranelate form. Clinical trial data showed that patients taking strontium ranelate had a higher rate of heart attacks compared to placebo: 1.7% versus 1.1%. The risk was especially pronounced in people with elevated diastolic blood pressure (90 mmHg or above), where the odds of heart attack more than tripled. The European Medicines Agency responded by restricting strontium ranelate to patients with severe osteoporosis who have no history of heart disease, peripheral artery disease, or stroke.
Whether these cardiovascular risks apply to strontium citrate is genuinely unclear. Health Canada conducted a safety review and found no reports of heart or circulatory side effects associated with strontium citrate, strontium lactate, or strontium gluconate at the doses found in supplements. The review also noted that no data existed on cardiovascular risk with any form of strontium at doses below 680 mg of elemental strontium per day, which is the prescription dose of ranelate. Supplement doses are typically lower.
Still, Health Canada took a precautionary stance. It recommended that any strontium supplement providing more than 4 mg of elemental strontium per day carry a label warning consumers not to use the product if they have, or are at high risk for, heart disease, circulatory problems, or blood clots. Most strontium citrate supplements on the market provide far more than 4 mg, so this warning effectively applies to all of them.
Timing and Absorption
Because strontium and calcium compete for absorption in the gut, the two should not be taken at the same time. The standard recommendation from supplement manufacturers is to take strontium citrate on an empty stomach, separated from calcium supplements or calcium-rich foods by at least two to four hours. Many people take it at bedtime for this reason, well after their last meal or calcium supplement of the day.
Most strontium citrate supplements provide between 200 and 700 mg of elemental strontium per day, though there is no established recommended daily allowance for strontium. The doses used in the prescription ranelate trials provided 680 mg of elemental strontium daily, which is at the high end of what some supplement products suggest.
Who Should Be Cautious
Strontium is cleared from the body by the kidneys, so people with significant kidney impairment should be cautious, as strontium could accumulate to higher-than-intended levels. The cardiovascular concerns outlined above mean anyone with a history of heart attack, stroke, blood clots, peripheral artery disease, or uncontrolled high blood pressure should avoid strontium in any form until more safety data exists.
Common side effects reported with strontium ranelate in clinical trials included nausea, diarrhea, and headache. Whether strontium citrate at supplement doses causes these effects at the same rate is unknown, since it hasn’t been studied in controlled trials. Anecdotally, digestive discomfort is the most frequently mentioned complaint among supplement users.