Prolia is a prescription injection used to treat osteoporosis and prevent fractures in people whose bones have become dangerously thin. It’s given as a single shot under the skin once every six months, and it works by slowing down the natural process that breaks down bone. While osteoporosis in postmenopausal women is its most well-known use, Prolia is approved for several other conditions where bone loss puts people at high risk of fractures.
All Five Approved Uses
Prolia is FDA-approved for five specific situations, all tied to bones that are weakening fast enough to make fractures likely:
- Postmenopausal osteoporosis in women at high risk for fracture
- Osteoporosis in men at high risk for fracture
- Steroid-induced osteoporosis in men and women taking glucocorticoid medications (like prednisone) who are at high risk for fracture
- Bone loss in men with prostate cancer who are receiving hormone-blocking therapy (androgen deprivation) for nonmetastatic disease
- Bone loss in women with breast cancer who are taking aromatase inhibitor therapy
The last two categories exist because certain cancer treatments accelerate bone loss as a side effect. Hormone-blocking therapies for prostate and breast cancer strip the body of hormones that help maintain bone density, sometimes causing rapid thinning that mimics osteoporosis. Prolia counteracts that specific problem.
How It Protects Bone
Your body constantly rebuilds bone through a cycle: specialized cells called osteoclasts break down old bone, and other cells called osteoblasts build new bone in its place. In osteoporosis, the breakdown side of this equation outpaces the rebuilding side, and bones gradually become porous and fragile.
Prolia is a lab-made antibody that intercepts a protein your body uses to activate those bone-breaking cells. Normally, bone-building cells release a signaling molecule that latches onto receptors on bone-breaking cells, switching them on. Prolia binds to that signaling molecule first, blocking the message from being delivered. Without that activation signal, fewer bone-breaking cells mature, and the ones that do are less active and die sooner. The result is slower bone loss and, over time, measurably denser bones.
How Well It Works
In clinical trials of postmenopausal women with osteoporosis, Prolia reduced the risk of new spinal fractures by about 68% compared to placebo. That translates to roughly 1 in 21 women avoiding a spinal fracture over the course of the study who would have had one otherwise. The benefits extended beyond the spine: hip fractures and other non-spinal fractures also decreased, though the effect was smaller. For hip fractures specifically, about 1 in 230 women benefited, reflecting the fact that hip fractures are less common to begin with.
What Getting the Injection Looks Like
Prolia is a 60 mg injection given under the skin every six months. Your healthcare provider administers it in the upper arm, thigh, or abdomen. It’s not a self-administered shot; you’ll go to a clinic or office twice a year. If you miss a dose, you can get the injection as soon as possible and then resume the six-month schedule from that date.
Before starting Prolia, your calcium and vitamin D levels need to be in a healthy range. Most people are advised to take 1,000 to 1,200 mg of calcium daily (from food and supplements combined) and maintain vitamin D levels above 20 to 30 ng/mL, often with a daily supplement of at least 800 IU. People with poor kidney function need especially close monitoring because they face a higher risk of dangerously low calcium levels during treatment.
Common and Serious Side Effects
The most frequently reported side effects include back pain, pain in the arms or legs, high cholesterol, muscle pain, and bladder infections. These are generally mild and manageable.
Two rare but serious risks deserve attention. The first is osteonecrosis of the jaw, a condition where part of the jawbone breaks down and dies. This causes pain, numbness in the mouth, and can make swallowing and speaking difficult. The risk is low in people using Prolia for osteoporosis, but it’s notably higher in cancer patients receiving higher doses of similar drugs. A National Cancer Institute study found that among people with metastatic breast cancer taking bone-modifying medications, nearly 9% developed jaw osteonecrosis, and those on denosumab (the active ingredient in Prolia) were about five times more likely to develop it than those on an older class of bone drugs called bisphosphonates. The risk also climbs with each year on treatment.
The second rare concern is atypical femur fractures, unusual breaks in the thigh bone that can occur with minimal trauma. These are uncommon but have been documented with long-term use.
Who Should Not Take Prolia
Prolia is not safe for everyone. It’s contraindicated if you have low blood calcium that hasn’t been corrected, since the drug can push calcium levels even lower. It’s also contraindicated during pregnancy because it can harm a developing fetus. Women of reproductive age typically need a pregnancy test before starting treatment. Anyone who has had a serious allergic reaction to Prolia or any of its ingredients, including anaphylaxis or facial swelling, should not receive it again.
The Rebound Problem When Stopping
One of the most important things to understand about Prolia is what happens when you stop it. Unlike some osteoporosis treatments that leave a lasting effect in bone, Prolia’s protection fades quickly once injections end. Within about 18 months of the last dose, bone density can drop rapidly, sometimes falling below where it was before treatment started. Worse, this rebound effect can trigger multiple spinal fractures in a short period.
The UK’s Medicines and Healthcare products Regulatory Agency documented 44 cases of vertebral fractures, including multiple fractures in the same person, after patients stopped or delayed their Prolia injections. Some occurred within the first nine months. People who already had a prior spinal fracture face the highest risk. This means Prolia is generally considered a long-term or even indefinite commitment. If you and your provider decide to stop, a transition plan is essential, typically involving switching to a bisphosphonate medication to maintain bone density during the vulnerable period after the last Prolia injection.