Key Takeaways

• Alendronate (brand name Fosamax) is an FDA-approved medication used to treat and prevent osteoporosis by slowing the cells that break down bone (1).

• In clinical trials, alendronate cut hip and wrist fracture risk roughly in half over 3 to 4 years of treatment (2).

• The standard dose is 70 mg once weekly for treatment or 35 mg once weekly for prevention, taken on an empty stomach first thing in the morning (3).

• Common side effects are digestive: stomach pain, acid reflux, and nausea. Serious but rare side effects include jaw osteonecrosis and atypical femur fractures (4, 5).

Alendronate is one of the most widely prescribed medications for osteoporosis, and the research behind it is strong. In clinical trials, it reduced the risk of hip and wrist fractures by about 50% in women with osteoporosis (2). It is FDA-approved for treating and preventing postmenopausal osteoporosis, male osteoporosis, steroid-induced osteoporosis, and Paget's disease of bone (1).

The medication works by slowing down the cells that break down bone, giving your body a better chance to maintain and rebuild bone density. Most people take it as a once-weekly tablet, and while it does come with some important rules around how you take it, it is generally well-tolerated when those guidelines are followed (4).

What Is Alendronate?

Alendronate belongs to a class of medications called bisphosphonates. These drugs work by slowing down bone loss, which helps maintain or rebuild bone density over time (1).

Your bones are constantly being remodeled. Old bone gets removed by cells called osteoclasts, and new bone gets formed by cells called osteoblasts. In osteoporosis, this process tips too far toward removal, meaning bone is broken down faster than it is rebuilt. Alendronate slows the removal side of that equation, helping to shift the balance back toward maintaining bone density (1).

It is prescribed for several conditions: postmenopausal osteoporosis (both treatment and prevention), osteoporosis in men, bone loss caused by long-term corticosteroid use (like prednisone), and Paget's disease of bone, a condition that disrupts normal bone remodeling (1).

How Effective Is Alendronate at Preventing Fractures?

The strongest evidence comes from the Fracture Intervention Trial (FIT), one of the largest studies on alendronate. The key finding: alendronate cut the risk of hip fractures and wrist fractures roughly in half compared to placebo in appropriately selected patients with osteoporosis (2).

For vertebral fractures (fractures of the spine), 8% of women taking alendronate experienced a new fracture over the study period, compared to 15% of women on placebo. For all clinical fractures combined, the rate was 13.6% with alendronate versus 18.2% with placebo (2).

In practical terms, this means that for every 100 women with osteoporosis taking alendronate over 3 to 4 years, roughly 5 fewer will experience a fracture compared to those not taking the medication.

How Should You Take Alendronate?

Alendronate has specific rules around how you take it, and following them matters both for the drug to work properly and to avoid digestive side effects.

Take it first thing in the morning on an empty stomach with a full glass of plain water. Do not use coffee, juice, milk, or mineral water, as these reduce how much your body absorbs (3).

Wait at least 30 minutes before eating, drinking anything else, or taking any other medications or supplements, including calcium and vitamins (3).

Stay upright (sitting or standing) for at least 30 minutes after taking it. Do not lie back down. This helps the tablet reach your stomach and prevents irritation to your esophagus (3).

These rules are not optional. In clinical practice, one of the most common mistakes I see is patients taking it with something other than plain water or lying down too soon afterward. Incorrect administration can make digestive side effects much more likely, although some patients can still have GI symptoms even when taking it correctly.

What Is the Right Dose?

The dose depends on whether you are treating or preventing osteoporosis.

The right dose for you is whatever your provider prescribes based on your individual situation. The doses below are the most commonly prescribed regimens, which generally vary depending on whether alendronate is being used to treat or prevent osteoporosis.

For treatment of osteoporosis, providers commonly prescribe 70 mg once weekly or 10 mg once daily (3).

For prevention of osteoporosis, common regimens are 35 mg once weekly or 5 mg once daily (3).

For steroid-induced osteoporosis, providers often prescribe 5 mg daily, or 10 mg daily for postmenopausal women not on hormone replacement therapy (3).

For Paget's disease, a typical regimen is 40 mg daily for 6 months (3).

The once-weekly option is commonly prescribed because it is easier to stick with. In a preference study, 86% of patients preferred the weekly dose over daily, and 89% said it was more convenient (7). The once-weekly and daily regimens produce equivalent bone density improvements at one year (6).

Why Does a Once-Weekly Dose Work?

This is one of the more interesting things about alendronate. After you take it, the drug binds to active bone remodeling sites and stays there for weeks. Since the bone-resorbing cells (osteoclasts) take 2 to 3 weeks to complete their cycle, a single weekly dose is enough to keep them suppressed continuously (6).

Taking 70 mg once a week delivers the same total drug exposure as 10 mg daily, and because alendronate stays active at bone sites for longer than the osteoclast lifecycle, weekly dosing effectively provides the same continuous protection as daily dosing (6).

Side Effects of Alendronate

Most side effects are digestive, and most are mild when you follow the administration instructions properly.

Common Side Effects (1-10% of patients): Stomach pain, acid reflux, nausea, bloating, constipation, diarrhea, and gas. Some people also experience heartburn or mild esophageal irritation (4).

Serious but Rare Side Effects: Osteonecrosis of the jaw (ONJ) is a condition where bone in the jaw breaks down, causing pain and swelling. It is rare in people taking oral bisphosphonates for osteoporosis. Your dentist should be aware that you are taking a bisphosphonate, and good dental care is important before and during treatment (5).

Atypical femur fractures are unusual fractures in the thigh bone that can occur with minimal trauma. They are rare but have been reported with long-term bisphosphonate use. Warning signs include a dull, aching pain in the thigh that starts weeks or months before the fracture occurs (4).

Severe bone, muscle, or joint pain can develop days, months, or even years after starting alendronate. If you experience severe pain at any point during treatment, contact your provider (4).

Who Should Not Take Alendronate?

Alendronate is not appropriate for everyone. You should avoid it if you have esophageal problems like achalasia (a swallowing disorder) or esophageal stricture, or if you cannot sit or stand upright for at least 30 minutes after taking it (8).

People with severe kidney problems should discuss alternatives with their provider, as alendronate is not recommended in this group particularly in more advanced renal impairment (8).

If you have active stomach or esophageal conditions like Barrett's esophagus, gastritis, or ulcers, use alendronate with caution, as it may worsen these issues (8).

How Long Should You Take Alendronate?

This depends on your fracture risk. Current guidelines suggest that people at low risk for fractures should consider stopping after 3 to 5 years and having their risk reassessed periodically (1).

One advantage of alendronate is that its effects persist even after you stop taking it, because the drug accumulates in bone and continues to provide anti-fracture benefits for a period after discontinuation. This makes "drug holidays" a common strategy, where you take a break from the medication under your provider's guidance and resume if your bone density begins declining again (1).

In practice, this decision should be individualized based on fracture history, bone density, age, and overall risk. This is not a medication I want patients starting or stopping on their own.

How Much Does Alendronate Cost?

Because pricing and availability can vary by pharmacy and by state, the most accurate way to see current costs is to compare pharmacy pricing directly from your Mochi account or to speak with your provider, who can review options with you.

How to Get Alendronate

Through Mochi Health, you start with an online consultation with an independent licensed provider. If your provider determines that alendronate is appropriate for your bone health, they can write a prescription and the medication is shipped to you.

Alendronate requires a prescription in the United States. Your provider will typically want to review your bone density results (a DEXA scan) and fracture risk factors before prescribing.

Frequently Asked Questions

Can I take alendronate with food or other medications?

No. Alendronate must be taken on an empty stomach with plain water only. Wait at least 30 minutes before eating, drinking anything else, or taking other medications. Food, coffee, juice, and supplements significantly reduce absorption.

What happens if I miss a weekly dose?

Take the missed dose the morning after you remember, then return to your regular weekly schedule. Do not take two doses on the same day (3).

How long does it take for alendronate to start working?

Bone density is typically assessed 6 to 12 months after starting treatment. Fracture risk reduction builds over the first few years of treatment (1).

Should I take calcium and vitamin D while on alendronate?

Yes. Adequate calcium and vitamin D are important for bone health. However, do not take calcium supplements within 30 minutes of your alendronate dose, as calcium interferes with absorption. Whether supplementation is needed can vary depending on dietary intake and lab findings (3).

Is it safe to have dental work done while taking alendronate?

Have a dental exam and complete any needed work before starting alendronate. While on the medication, maintain good oral hygiene and tell your dentist you are taking a bisphosphonate before any procedures (5).

Can alendronate be taken during pregnancy?

Discuss this with your provider. Alendronate may remain in your body for years after you stop taking it, so even if you plan to become pregnant in the future, let your provider know (8).

Check Your Eligibility

If you are concerned about your bone health and wondering whether alendronate might be right for you, an independent licensed provider on Mochi Health's telehealth platform can evaluate your situation and discuss treatment options. Check your eligibility here.

Disclaimer: This article is for educational purposes only and should not be considered medical advice. The information provided does not constitute recommendations for treatment. Always consult with your healthcare provider about your specific situation, symptoms, and treatment options.

References

1. Parker LRW, et al. Alendronate. StatPearls. 2023.

2. Black DM, et al. Fracture risk reduction with alendronate in women with osteoporosis: the Fracture Intervention Trial. J Clin Endocrinol Metab. 2000;85(11):4118-24.

3. Mayo Clinic. Alendronate (oral route). Mayo Clinic. 2026.

4. Drugs.com. Alendronate Side Effects. Drugs.com. 2025.

5. MedlinePlus. Alendronate: MedlinePlus Drug Information. National Library of Medicine. 2024.

6. Rodan GA, Fleisch HA. Update on alendronate for osteoporosis: once-weekly dosing. Am J Med. 2001;111(7):583-4.

7. Simon JA, et al. Patient preference for once-weekly alendronate 70 mg versus once-daily alendronate 10 mg. Clin Ther. 2002;24(11):1871-86.

8. U.S. Food and Drug Administration. Fosamax (alendronate sodium) tablets label. FDA. 2012.