Alendronate: what it treats, how to take it, side effects
Last updated September 3, 2026.
Alendronate is a bisphosphonate - it prevents bone breakdown and increases bone density. You may know it as Fosamax. The medication with the ritual: plain water, empty stomach, upright for 30 minutes - and the ritual is the whole safety story.
What does it treat?
Osteoporosis - bones grown thin and break-prone - treatment and prevention, and Paget's disease of bone.
How do you take it?
First thing in the morning, empty stomach, with a full glass of plain water - 6 to 8 ounces; never coffee, tea, juice, milk, or mineral water: they block absorption. Then: nothing to eat, drink, or take - no other medications, vitamins, or antacids - for at least 30 minutes, and no lying down: sit or stand upright until those 30 minutes pass and you have eaten. Swallow tablets whole - never split, chew, crush, or suck them. The weekly 70 mg tablet and the daily tablets run the same rules. The reason is the esophagus: a pill that lingers there can burn it badly. Missed weekly dose: take it the morning you remember, then return to your schedule - never two on the same day.
Side effects to know
- Common: stomach upset, nausea, stomach pain, constipation, diarrhea, gas, and muscle or joint pain.
- Serious - call your doctor immediately, before any more doses: new or worsening heartburn, difficulty or pain when swallowing, chest pain; bloody vomit or coffee-ground vomit, or black, tarry, or bloody stools; allergic signs - rash, blisters or peeling skin, hives, itching, trouble breathing, hoarseness, swelling of eyes, face, lips, tongue, or throat; the jaw warning - painful or swollen gums, loosening teeth, numbness or heaviness in the jaw, poor jaw healing; eye pain; and dull, aching pain in the hips, groin, or thighs - the thigh-bone stress signal.
Who should not take it?
Anyone who cannot sit or stand upright for 30 minutes, anyone with esophagus problems, low blood calcium, or a risk of aspirating food or fluids - your doctor may rule it out. Kidney disease changes the choice. Dental work belongs before or between, with the dentist told you take a bisphosphonate - the jaw-healing issue is real around extractions. If you become pregnant, call your doctor.
When is it an emergency?
Throat swelling, trouble breathing, vomit that looks like coffee grounds, or black stools is a 911 call. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why all the rules - water, empty stomach, staying upright?
Two problems, one ritual. Absorption: food, coffee, juice, and even mineral water nearly zero the dose - plain water only, first thing, empty stomach. Esophagus safety: the tablet can burn the esophagus if it lingers, so a full 6 to 8 ounces of water and 30 minutes upright - no lying down, no eating, no other pills - march it to the stomach. MedlinePlus says esophagus problems or an inability to stay upright can rule the drug out entirely.
What is the jaw problem I have heard about?
Osteonecrosis of the jaw: rare poor-healing of jaw bone after dental work, linked to bisphosphonates - the warning signs are painful or swollen gums, loosening teeth, jaw numbness or heaviness, and slow healing after an extraction. The practical rule: major dental work gets planned with your doctor and dentist talking, and every dentist you see knows you take this drug. Good dental hygiene on a bisphosphonate is prevention, not cosmetics.
What is the thigh-pain warning?
Atypical femur fracture: long-term bisphosphonates can, rarely, produce stress fractures in the thigh bone - and the bone often announces it first with a dull, aching pain in the hip, groin, or thigh, weeks or months before any break. That pain pattern on alendronate gets reported and imaged, not stretched out. The flip side is on the same label: people with osteoporosis break these bones without the drug too - which is the risk-balance your doctor runs.
Why is it weekly - and what if I forget which day?
The drug parks in bone for a long time, so a weekly 70 mg dose keeps the coverage without a daily ritual. Pick a fixed morning and alarm it. Missed the day? Take it the next morning you remember - then resume the original day. Never take two tablets the same day. A missed week costs little; a doubled dose buys the esophagus risk for nothing.
How long do people stay on alendronate?
Years, but not automatically forever: the fracture-protection evidence is strongest in the first years, and the rare jaw and thigh risks accumulate - so guidelines run a periodic risk review, and some patients take a planned "drug holiday" after several years under their doctor's direction. The answer at each annual visit is a decision, not a default. Bone-density scans are the scorecard.
What happens if I miss a dose of alendronate?
Weekly tablet: take it the morning you remember - plain water, empty stomach, upright 30 minutes, all the rules - then return to your usual day. Daily tablet: skip the missed one and take the next as scheduled. Either way: never two tablets in one day. The ritual matters more than the calendar.