Denosumab is an injectable medication used primarily to treat osteoporosis and to prevent bone complications in people with cancer. It works by slowing down the natural process of bone breakdown, which strengthens bones and reduces fracture risk. Depending on the condition being treated, it’s sold under two different brand names at two different doses.
How Denosumab Works
Your bones are constantly being broken down and rebuilt. Specialized cells called osteoclasts handle the breakdown side, dissolving old bone so new bone can replace it. In osteoporosis and in cancers that spread to bone, this demolition process runs ahead of rebuilding, leaving bones weak and fragile.
Denosumab is a lab-made antibody that blocks a specific protein your body uses to activate those bone-dissolving cells. By intercepting that signal, it prevents osteoclasts from maturing, reduces their activity, and slows bone loss. The result is denser, stronger bone and fewer fractures. It also blocks the formation of new osteoclasts from precursor cells, so the effect is comprehensive rather than partial.
Osteoporosis and Bone Loss
Under the brand name Prolia, denosumab is approved for several forms of bone loss:
- Postmenopausal osteoporosis in women at high risk for fracture
- Osteoporosis in men at high risk for fracture
- Glucocorticoid-induced osteoporosis in men and women who take steroid medications long-term and face high fracture risk
- Bone loss from hormone therapy, specifically in men receiving androgen deprivation therapy for prostate cancer and women on aromatase inhibitor therapy for breast cancer
In a landmark trial of postmenopausal women treated for three years, denosumab reduced vertebral (spinal) fractures by 68%, hip fractures by 40%, and fractures at other sites by 20% compared to placebo. Those are among the strongest fracture-reduction numbers seen with any osteoporosis treatment.
Prolia is given as a single injection under the skin once every six months, typically in the upper arm, thigh, or abdomen. A healthcare professional administers it, so there are no pills to remember daily. If you miss a scheduled dose, you receive the injection as soon as possible and then resume the six-month cycle from that date.
Cancer-Related Bone Complications
Under the brand name Xgeva, denosumab is used at a higher dose for more aggressive bone problems tied to cancer:
- Bone metastases from solid tumors and multiple myeloma, where the goal is preventing fractures, spinal cord compression, and the need for radiation or surgery to bone
- Giant cell tumor of bone, a rare tumor that destroys bone tissue, in adults and skeletally mature adolescents whose tumor can’t be surgically removed or where surgery would cause severe harm
- Hypercalcemia of malignancy that hasn’t responded to other bone-protecting drugs
For bone metastases, Xgeva is injected every four weeks. For giant cell tumor of bone, the schedule is the same but includes extra loading doses on days 8 and 15 of the first month. Both are subcutaneous injections, not infusions, so they take only a few minutes.
Important Risks and Side Effects
The most significant risk is a drop in blood calcium levels, called hypocalcemia. Because denosumab powerfully slows bone breakdown, it reduces the amount of calcium released into the bloodstream. For most people this is manageable with calcium and vitamin D supplements. However, the FDA added its strongest warning (a Boxed Warning) for patients with advanced chronic kidney disease, particularly those on dialysis. In these patients, severe hypocalcemia can lead to seizures and dangerous heart rhythm changes. The risk peaks around two weeks after each injection and stays elevated through roughly week ten.
Osteonecrosis of the jaw (ONJ) is another serious side effect. This condition involves exposed, dying bone in the jaw that causes pain, numbness, and difficulty swallowing or speaking. It was long considered rare, but a study of breast cancer patients receiving bone-modifying drugs found ONJ in about 9% of participants overall. Among those taking denosumab specifically, 12% developed ONJ, compared to 3% of those on an older class of bone-protecting drugs. Patients who switched from that older therapy to denosumab had the highest rate at 16%. The risk stays low during the first year but climbs with each additional year of treatment. Gum disease and tooth infections are major risk factors, so dental health matters before and during treatment.
Why You Can’t Just Stop Taking It
One of the most important things to know about denosumab is that stopping it abruptly can be dangerous. Once the drug clears your system, bone-dissolving cells rebound aggressively, breaking down bone faster than they did before you ever started treatment. Markers of bone breakdown rise above their original levels, creating a state of accelerated bone loss.
This rebound effect can cause rapid loss of the bone density you gained, and it raises the risk of multiple spinal fractures occurring in a short period. For this reason, if you and your doctor decide to stop denosumab, the standard approach is to transition to another class of bone-protecting medication (typically an oral bisphosphonate) to prevent that rebound. Missed or delayed injections carry the same risk, so staying on schedule is critical.
Who Should Be Cautious
Before starting denosumab for osteoporosis, your kidney function should be checked. People with advanced kidney disease face a much higher risk of dangerous calcium drops, and treatment in that population should involve a specialist experienced in managing the mineral and bone complications of kidney disease. Correcting any existing calcium deficiency and starting supplements before the first injection can reduce, though not eliminate, the risk.
Dental problems also warrant attention. Because ONJ risk increases with treatment duration and is linked to pre-existing gum disease or infections, getting dental issues addressed before beginning therapy is a practical step.
Biosimilar Options
Several biosimilar versions of denosumab have received FDA approval starting in 2025, with products approved as alternatives to both the Prolia and Xgeva formulations. Biosimilars are not generic drugs in the traditional sense, but they are rigorously tested to perform the same way as the original. Their arrival is expected to increase access and lower costs for patients who need long-term treatment.