Short answer: Prolia and Fosamax are different prescription medicines for postmenopausal osteoporosis. The Prolia website reports a real-world study in which 10.5% of women on Prolia had a major osteoporotic fracture, compared with 17.2% of women on alendronate (Fosamax), so the one fracture comparison it cites favors Prolia. The right choice depends on your fracture risk and history, and that is a decision to make with your clinician.
Are denosumab and Prolia the same?
Prolia is a denosumab product, but denosumab is the active ingredient in other products too, such as XGEVA. Prolia’s website says not to receive other denosumab products at the same time.
Prolia vs Fosamax: which is safer?
The fracture data and the safety information answer different questions. The Prolia website reports a real-world fracture comparison, and it reports a 1-year trial that measured bone density. The real-world study measured fractures, not side effects. Fosamax has its own warnings, which are in its prescribing information, so check those with your pharmacist before you compare.
The real-world study the Prolia website reports
The Real-World Study Results page on the Prolia website describes what it calls the largest real-world study of postmenopausal women with osteoporosis. It compared fracture rates in women taking Prolia with women taking alendronate, commonly known as Fosamax, using fracture information collected from January 2012 through December 2019. The overall risk of major osteoporotic fracture was 10.5% for women on Prolia and 17.2% for women on alendronate. Major osteoporotic fracture includes fractures of the hip, spine and arm bones. This is a real-world study reported by the maker, not a controlled trial, and the page says real-world evidence “is not meant to replace clinical trials.”
The 1-year trial that measured bone density
The Study Design page on the Prolia HCP website describes a 1-year, international, randomized, double-blind phase 3 trial in postmenopausal women previously treated with alendronate. It compared continuing alendronate with transitioning to Prolia. The primary endpoint was the percent change in total hip bone mineral density from baseline to month 12. The trial is published as Kendler DL, Roux C, Benhamou CL, et al., J Bone Miner Res. 2010;25:72-81. Bone density is a different measurement from fracture risk, so this trial answers a different question than the real-world study.
What are the Prolia side effects?
As of November 2026, the Important Safety Information on the Prolia website lists the most common side effects below, by group.
| Group | Most common side effects listed |
|---|---|
| Women after menopause with osteoporosis | Back pain, pain in arms and legs, high cholesterol, muscle pain, bladder infection |
| Men with osteoporosis | Back pain, joint pain, common cold (runny nose or sore throat) |
| Corticosteroid-induced osteoporosis | Back pain, high blood pressure, lung infection (bronchitis), headache |
| Prostate or breast cancer treatment | Joint pain, back pain, pain in arms and legs, muscle pain. Men with nonmetastatic prostate cancer receiving ADT had a greater incidence of cataracts. |
The same label lists serious risks you should know before starting.
| Serious warning | What the label says |
|---|---|
| Low blood calcium (hypocalcemia) | Prolia may lower calcium. Existing low calcium must be treated first. Call your doctor for muscle spasms, twitches or cramps, or numbness or tingling in fingers, toes or around the mouth. |
| Severe low calcium with advanced kidney disease | Prolia may increase the risk of severe low calcium, which can result in hospitalization, life-threatening events and death. |
| Allergic reactions | Call your doctor or go to the nearest emergency room for low blood pressure, trouble breathing, throat tightness, swelling of face, lips or tongue, rash, itching or hives. |
| Jaw bone problems (osteonecrosis) | Your doctor should examine your mouth before you start, and you should practice good mouth care during treatment. |
| Unusual thigh bone fractures | Symptoms include new or unusual pain in your hip, groin or thigh. |
| Broken bones after stopping or delaying | Your risk of breaking bones, including spine bones, increases after treatment stops or a dose is skipped or delayed. Do not stop, skip or delay Prolia without first talking with your doctor. |
| Serious infections | Infections of the skin, abdomen, bladder or ear may happen, and endocarditis was reported more often with Prolia. |
| Skin problems and pain | Dermatitis, rash and eczema have been reported. Some people develop severe bone, joint or muscle pain. |
The label also says it is not known whether long-term use may slow healing of broken bones, and that pancreatitis has been reported with Prolia.
How long do Prolia side effects last after an injection?
The Important Safety Information on the Prolia website does not give how long side effects last after an injection. Use the warnings above to know which symptoms need a prompt call, and ask your prescriber how long a side effect usually lasts for you. Report serious side effects to the FDA through FDA MedWatch.
Who should not get Prolia?
The Prolia label says not to take Prolia if you have low blood calcium, if you are pregnant or plan to become pregnant, or if you are allergic to denosumab or any ingredient in Prolia. Tell your doctor before starting if you:
- are taking other denosumab products
- cannot take daily calcium and vitamin D
- had parathyroid or thyroid surgery
- have trouble absorbing minerals (malabsorption syndrome)
- have kidney problems or are on dialysis
- take a medicine that can lower blood calcium
- plan dental surgery or tooth removal
- are breastfeeding or plan to
If you can become pregnant, the label says your provider should run a pregnancy test before treatment, and that you should use effective birth control during treatment and for at least 5 months after your last dose.
Who is Prolia prescribed for?
The Prolia label lists use in women after menopause who are at high risk for fracture, or who cannot use another osteoporosis medicine or for whom other medicines did not work well. It also lists men with osteoporosis at high fracture risk, people who will take corticosteroids such as prednisone for at least six months, and men and women at high fracture risk who have bone loss from certain prostate or breast cancer treatments.
Fosamax side effects, Boniva and Actonel
Fosamax’s full side effect list and warnings are in its own prescribing information. Bring that to your pharmacist and compare it with the Prolia tables above. Boniva and Actonel have their own labels, which list their side effects. The Prolia label notes that other osteoporosis medicines exist, and those are the names this page can point you toward.
What are the Evenity side effects compared with Prolia?
The Prolia HCP study page carries a safety box for Evenity, headed “POTENTIAL RISK OF MYOCARDIAL INFARCTION, STROKE, AND.” The same page carries a Prolia box on severe low calcium in patients with advanced kidney disease. For the full Evenity warning, read Evenity’s own prescribing information before you compare it with Prolia.
What are alternatives to Prolia and Fosamax?
The Prolia label shows that other osteoporosis medicines exist, and which one fits depends on your fracture risk and history. Two everyday steps are also worth knowing about. The NIA says calcium and vitamin D can help build strong bones, and the Prolia label says your doctor may prescribe them with Prolia. The NIA also advises talking with your health care provider before starting any new supplement. Second, falls threaten bone health. The CDC says there are proven ways to reduce and prevent falls, on its CDC older adult fall prevention page, and the NIA’s room-by-room fall prevention guide lists practical changes for each area of the home.
What does Prolia cost?
As of November 2, 2026, the Prolia website says you may pay as little as $0 out of pocket for each dose through the Amgen SupportPlus Co-Pay Program, if you are a commercially insured patient who is eligible. The website says eligibility criteria and program maximums apply, and it lists the full terms at www.amgensupportplus.com/copay. Prices and program terms change, so check your exact out-of-pocket amount with your pharmacy or the program before you plan around it.
For Fosamax, ask your pharmacy for the current price. The NIA says generic drugs are usually less expensive than their brand-name counterparts, and suggests asking your doctor whether a generic drug or a less expensive brand-name medicine is available.
How do I get Prolia or Fosamax safely?
Both are prescription medicines. The NIA explains that prescription drugs are medicines you can get only with a doctor’s order. It warns that medicines from a fake online pharmacy can be ineffective, unsafe or dangerous, and says to look for a pharmacy that requires a valid prescription, is licensed in your state, and has a pharmacist available to answer questions. Read the full guidance in NIA’s Taking Medicines Safely as You Age.
What should you ask before you decide?
- Ask whether your fracture risk, kidney function and calcium levels point to Prolia or to Fosamax.
- Ask whether you need a dental exam before starting Prolia, given its jaw bone warning.
- Ask how long side effects usually last and which symptoms need a call right away.
- Ask for the current prescribing information for each medicine you are considering.
- Ask for today’s out-of-pocket cost for each option.
Bring this list and your medicine history to your next appointment, then compare the answers side by side.
By HealthDataConsortium.org Research Team
This article is for general information purposes only and does not constitute medical advice. Consult your doctor or qualified healthcare provider before making changes to your health routine.
