Short answer: In the label's 3-year treatment trials, side effects judged drug-related were mostly stomach-related: abdominal pain (6.6% on Fosamax 10 mg vs 4.8% on placebo), musculoskeletal pain (4.1% vs 2.5%), nausea, dyspepsia, constipation and diarrhea. With weekly 70 mg, abdominal pain was 3.7%. Warnings cover esophagus irritation, low calcium, jaw bone death and unusual thigh fractures. There is no boxed warning.
What Fosamax is approved for: Fosamax is a bisphosphonate approved to treat and prevent osteoporosis in postmenopausal women, to increase bone mass in men with osteoporosis, to treat steroid (glucocorticoid)-induced osteoporosis in people taking the equivalent of 7.5 mg or more of prednisone a day with low bone density, and to treat Paget's disease of bone (sections 1.1 to 1.5). The label says the best length of use has not been set, and people at low fracture risk may be considered for stopping after 3 to 5 years (section 1.6).
Source
FOSAMAX (alendronate sodium) tablets, for oral use, prescribing information and Medication Guide. Organon. DailyMed, version published March 16, 2026. DailyMed setid 14e931fd-2c5f-4d90-b7db-5980706f4a56
No. The current Fosamax label has no boxed warning.
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Fosamax.
| Adverse reaction | Fosamax 10 mg/day for 3 years (n=196) | Placebo (n=397) | FIT: Fosamax 5 then 10 mg/day (n=3236) | FIT: Placebo (n=3223) |
|---|---|---|---|---|
| Abdominal pain | 6.6 | 4.8 | 1.5 | 1.5 |
| Nausea | 3.6 | 4.0 | 1.1 | 1.5 |
| Dyspepsia | 3.6 | 3.5 | 1.1 | 1.2 |
| Constipation | 3.1 | 1.8 | 0.0 | 0.2 |
| Diarrhea | 3.1 | 1.8 | 0.6 | 0.3 |
| Flatulence | 2.6 | 0.5 | 0.2 | 0.3 |
| Acid regurgitation | 2.0 | 4.3 | 1.1 | 0.9 |
| Esophageal ulcer | 1.5 | 0.0 | 0.1 | 0.1 |
| Vomiting | 1.0 | 1.5 | 0.2 | 0.3 |
| Dysphagia | 1.0 | 0.0 | 0.1 | 0.1 |
| Abdominal distention | 1.0 | 0.8 | 0.0 | 0.0 |
| Gastritis | 0.5 | 1.3 | 0.6 | 0.7 |
| Musculoskeletal (bone, muscle or joint) pain | 4.1 | 2.5 | 0.4 | 0.3 |
| Muscle cramp | 0.0 | 1.0 | 0.2 | 0.1 |
| Headache | 2.6 | 1.5 | 0.2 | 0.2 |
| Dizziness | 0.0 | 1.0 | 0.0 | 0.1 |
| Taste perversion | 0.5 | 1.0 | 0.1 | 0.0 |
Values are percent of patients. The first two columns are the United States and Multinational 3-year studies; the last two are the Fracture Intervention Trial (FIT), where women took 5 mg a day for 2 years and then 10 mg a day for 1 or 2 more years. All-cause deaths were 1.8% in both groups, and stopping because of side effects was 8.9% on Fosamax vs 9.5% on placebo. The label adds that rash and redness have occurred.
| Adverse reaction | Once weekly Fosamax 70 mg (n=519) | Fosamax 10 mg/day (n=370) |
|---|---|---|
| Abdominal pain | 3.7 | 3.0 |
| Dyspepsia | 2.7 | 2.2 |
| Acid regurgitation | 1.9 | 2.4 |
| Nausea | 1.9 | 2.4 |
| Abdominal distention | 1.0 | 1.4 |
| Constipation | 0.8 | 1.6 |
| Flatulence | 0.4 | 1.6 |
| Gastritis | 0.2 | 1.1 |
| Gastric ulcer | 0.0 | 1.1 |
| Musculoskeletal (bone, muscle, joint) pain | 2.9 | 3.2 |
| Muscle cramp | 0.2 | 1.1 |
One-year study comparing Fosamax 70 mg once weekly with 10 mg daily. Values are percent of patients. The label says the overall safety of the two was similar.
| Adverse reaction | Fosamax 10 mg/day (n=146) | Placebo (n=95) | Once weekly Fosamax 70 mg (n=109) | Placebo (n=58) |
|---|---|---|---|---|
| Acid regurgitation | 4.1 | 3.2 | 0.0 | 0.0 |
| Flatulence | 4.1 | 1.1 | 0.0 | 0.0 |
| Gastroesophageal reflux disease | 0.7 | 3.2 | 2.8 | 0.0 |
| Dyspepsia | 3.4 | 0.0 | 2.8 | 1.7 |
| Diarrhea | 1.4 | 1.1 | 2.8 | 0.0 |
| Abdominal pain | 2.1 | 1.1 | 0.9 | 3.4 |
| Nausea | 2.1 | 0.0 | 0.0 | 0.0 |
A 2-year study of 10 mg daily and a 1-year study of 70 mg once weekly, each against placebo. Values are percent of patients. Stopping because of side effects: 2.7% on 10 mg/day vs 10.5% on placebo, and 6.4% on 70 mg weekly vs 8.6% on placebo.
Blood tests in controlled studies: mild, short-lived, symptom-free drops in calcium and phosphate in about 18% and 10% on Fosamax vs about 12% and 3% on placebo. Drops below 8.0 mg/dL calcium or to 2.0 mg/dL phosphate or less were similar in both groups.
Prevention trials in women 40 to 60 (5 mg a day for 2 or 3 years): stopping because of side effects was 7.5% on Fosamax vs 5.7% on placebo. In a 1-year study, 35 mg weekly and 5 mg daily had similar safety (Table 3).
Steroid-induced osteoporosis, 1-year studies (Table 5): abdominal pain 3.2% on 10 mg/day and 1.9% on 5 mg/day vs 0.0% on placebo; acid regurgitation 2.5% and 1.9% vs 1.3%; melena (dark, tarry stools) 1.3% and 0.0% vs 0.0%.
Paget's disease, 40 mg a day for 3 to 12 months: upper stomach and esophagus side effects 17.7% vs 10.2% on placebo; bone, muscle or joint pain about 6% vs about 1%; stopping because of side effects 6.4% vs 2.4%.
Reported after approval: allergic reactions including hives and swelling; short-lived muscle aches, tiredness, weakness and fever, usually at the start of treatment; esophagus inflammation, erosions, ulcers, narrowing or tears; stomach and duodenal ulcers; jaw osteonecrosis; severe bone, joint or muscle pain; joint swelling; unusual thigh fractures; dizziness and vertigo; asthma flare-ups; hair loss; severe skin reactions including Stevens-Johnson syndrome; eye inflammation (uveitis, scleritis); and bone damage in the outer ear canal.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Who should not use it. People with esophagus problems that slow emptying, such as a narrowing (stricture) or achalasia; people who cannot stand or sit upright for at least 30 minutes; people with low blood calcium; and anyone allergic to any part of the product.
Esophagus and stomach irritation. Fosamax can irritate the upper digestive tract. Esophagus inflammation, ulcers and erosions, sometimes with bleeding and rarely followed by narrowing or a tear, have been reported, some needing hospital care. The risk appears greater in people who lie down after a dose, do not take it with a full glass of water, or keep taking it after symptoms start. It is stopped for trouble or pain swallowing, chest pain behind the breastbone, or new or worse heartburn.
Low blood calcium. Low calcium is corrected before starting, and other mineral problems such as low vitamin D are treated. Small, symptom-free drops in calcium and phosphate can occur, especially in Paget's disease and in people on steroids.
Bone, joint and muscle pain. Severe, sometimes disabling pain has been reported with osteoporosis bisphosphonates, starting from one day to several months after the first dose. Fosamax is stopped if severe symptoms develop; most people improved after stopping.
Osteonecrosis of the jaw. Jaw bone death has been reported, usually with tooth extraction or local infection with slow healing. Risk factors include invasive dental work, cancer, chemotherapy, steroids, poor mouth care and gum disease. The risk may grow with longer use.
Unusual thigh and other fractures. Low-trauma fractures of the thigh bone shaft have been reported, sometimes on both sides, often after weeks to months of dull, aching thigh pain. New thigh or groin pain is checked for a fracture, and pausing the bisphosphonate is considered.
Kidney impairment. Fosamax is not recommended when creatinine clearance is under 35 mL/min.
Steroid-induced osteoporosis. Benefit at steroid doses under 7.5 mg of prednisone a day has not been established. Sex hormone status is checked before starting, and bone density is measured at the start and again after 6 to 12 months.
From the Medication Guide that comes with Fosamax:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.