If you accidentally took two Fosamax (alendronate) tablets, stay fully upright, drink a glass of milk or take an antacid to bind the drug, and do not make yourself vomit. Then call your doctor or poison control (1-800-222-1222 in the US, 1-844-764-7669 in Canada). The label says an overdose can lower your blood calcium and phosphate and cause stomach and esophagus problems such as heartburn or ulcers.
That advice sounds backwards, we know. You were told never to take Fosamax with milk or antacids. But an accidental double dose flips the rules: now you want calcium in your stomach, because the FDA label states that milk or antacids should be given to bind alendronate after an oral overdose. What blocks the drug on a normal day becomes first aid on a bad one.
How Much of an Extra Tablet Your Body Absorbs
Start with the numbers. According to the FDA prescribing information for Fosamax, women who took it after an overnight fast and two hours before breakfast absorbed about 0.64% of an oral dose on average. In other words, more than 99% of a tablet was not absorbed.
Of the small amount that is absorbed, part goes to bone and the rest leaves in the urine. In the FDA label, about 50% of a dose given into a vein was excreted in the urine within 72 hours. What reaches bone stays a long time: the label estimates a terminal half-life of more than 10 years, probably reflecting slow release from the skeleton.
Small absorption is not the whole story. The same label says an oral overdose may cause low blood calcium (hypocalcemia), low blood phosphate (hypophosphatemia), and upper stomach and esophagus problems such as upset stomach, heartburn, esophagitis, gastritis, or ulcer. It also notes: "No specific information is available on the treatment of overdosage with FOSAMAX."
Prolia (denosumab) works differently. It is an injection, not a bisphosphonate, and its label says fracture risk goes up after treatment stops, including several broken bones in the spine. Its patient guide says not to stop, skip or delay Prolia without first talking with your doctor. If you are on that one, see how late you can get your Prolia shot. Planning a tooth extraction on Prolia? See Prolia and dental work.
One published case gives a sense of scale. A 2021 conference abstract in European Psychiatry describes a 76-year-old woman who swallowed eight 70 mg alendronate tablets at once: eight weeks of medication in one sitting. In the emergency department she had gastric lavage (her stomach was washed out), activated charcoal, and an IV acid reducer. After 24 hours of observation and a psychiatric evaluation, she was discharged. That is one treated case, so it cannot tell you how any one person will react.
So take a breath, and then think about your esophagus.
Why Your Esophagus Needs Protecting
Alendronate can irritate the esophagus, the tube that carries food from your mouth to your stomach. A 1996 report in the New England Journal of Medicine looked at reports sent to the maker when an estimated 475,000 patients had been prescribed alendronate. 199 of those patients had esophagus problems. In 51 of them (26%), the problems were serious or severe, and 32 were hospitalized. Endoscopy generally showed chemical esophagitis, with erosions or ulcers.
The report linked these injuries to swallowing the tablet with little or no water, lying down during or after taking it, continuing to take it after symptoms began, and having esophagus problems already. Its authors recommended the rules the label carries today: 6 to 8 ounces of water on rising, staying upright for at least 30 minutes and until the first food of the day, and stopping the drug promptly if esophagus symptoms develop. We break down those rules in detail in our guide to how long after Fosamax you can eat or lie down.
After an overdose, the label says vomiting should not be induced and the person should remain fully upright, both "due to the risk of esophageal irritation." The first-aid steps below follow from that: protect the esophagus. On a normal day, the same risk is why taking Fosamax without enough water is a problem.
What to Do Right Now, Step by Step
The FDA label and MedlinePlus agree on the protocol. It has four moves.
- Stay fully upright. Sit or stand. Do not lie down, even if you feel queasy. After an overdose, the label says the person should remain fully upright, and MedlinePlus says not to let them lie down.
- Drink a full glass of milk or take a calcium-based antacid. MedlinePlus instructs giving a full glass of milk and calling poison control after an alendronate overdose. The label says milk or antacids bind alendronate. On a normal day, that is why calcium and antacids get in the way of absorption. After an overdose, that is the point.
- Do not make yourself vomit. Vomiting would bring the drug back up through your esophagus. The FDA label is explicit: vomiting should not be induced, and its patient guide says, "Do not try to vomit."
- Call your doctor or poison control. MedlinePlus says to call poison control after an overdose, and the label's patient guide says to call your doctor. If the person has collapsed or is not breathing, call 911. In the US, poison control is 1-800-222-1222. Canada's poison centres answer at 1-844-764-7669, or 1-800-463-5060 in Quebec.
One more label detail: the FDA prescribing information says dialysis would not be beneficial after an overdose.
Your Situation at a Glance
| What you did | What to do |
|---|---|
| Took two tablets on the same day | Stay upright, drink milk or take an antacid, do not make yourself vomit, and call your doctor or poison control (1-800-222-1222 in the US, 1-844-764-7669 in Canada) |
| Took two tablets in the same week, on different days | You still took more than prescribed, and the label's patient guide says to call your doctor if you take too much. Ask about next week's dose on that call, and watch for the symptoms below |
| Not sure whether you took a second one | Do not take another tablet "just in case." Count your remaining pills, then wait for your next scheduled day |
Whatever your row, watch for symptoms. If you get chest pain, new or worsening heartburn, or trouble or pain when you swallow, the patient guide in the FDA label says to stop taking Fosamax and call your doctor right away. It also says to call your doctor right away for symptoms of low blood calcium, such as muscle spasms, twitches or cramps, or numbness or tingling in your fingers, toes or around your mouth. MedlinePlus lists these possible signs of an alendronate overdose: nausea, heartburn, stomach pain, bloody vomit or vomit that looks like coffee grounds, bloody or black and tarry stool, and difficulty or pain when swallowing. It says bloody or coffee-ground vomit and black, tarry, or bloody stools mean calling your doctor immediately, before you take any more alendronate.
Why This Happens So Often (It Is Not Just You)
Doubling a weekly pill can feel like a personal failure. Mistakes with weekly pills are common, though, and researchers have counted them.
The GastroPASS study, published in JBMR Plus, followed 1,028 postmenopausal women taking a weekly effervescent alendronate tablet for about a year. 29.9% of them made at least one medication error. Nearly one in three. Most errors broke rules that apply to any oral bisphosphonate, such as what to drink it with, how much, and waiting 30 minutes before the first meal. 1.7% of the women made an error in the once-weekly dosing itself.
The pattern goes beyond alendronate. In a 2018 column in Pharmacy and Therapeutics, the director of error reporting programs at the Institute for Safe Medication Practices (ISMP) wrote that most harmful errors with low-dose methotrexate reported to ISMP since 1996 involved accidental daily dosing of a drug meant to be taken weekly. If that is the exact slip you made, here is what to do after taking methotrexate two days in a row.
Doubling up can happen on any schedule, which is why we built a full guide on what to do if you accidentally take any medication twice. Weekly drugs like alendronate and weekly injectables like Ozempic share the same trap: seven days is long enough to forget, short enough to second-guess. Even daily empty-stomach drugs are not immune, as anyone who has accidentally taken a double dose of levothyroxine can tell you.
Next Week's Dose: Re-Anchor, Do Not Shift
After the scare passes, one practical question remains: what happens to your schedule?
The closest written rule is the one for a missed dose. MedlinePlus says to never take more than one dose in one day, and to return to taking one dose each week on your regularly scheduled day. The FDA label says the same thing: patients should return to one dose once a week, as originally scheduled on their chosen day.
That rule was written for a missed dose, so treat it as a starting point and ask. When you call your doctor about the extra tablet, ask about next week too. Do not skip next week to "balance out" the extra tablet or shift your day on your own: MedlinePlus says not to stop taking alendronate without talking to your doctor.
The mirror scenario follows the same logic. If you ever miss a week entirely, the fix is also anchored to your chosen day, and we cover it in our guide to handling a missed dose of Fosamax.
How to Keep This From Happening Again
A weekly pill gets no daily repetition, so it helps to take memory out of the job. Two things do that.
The first is a reminder that refuses to be ignored. Pillo's persistent alarm keeps ringing until you act on it, and it handles weekly schedules natively, so your Fosamax alert fires on your chosen morning and only that morning. The second is a dose log. Once you mark a dose taken in Pillo, the answer to "wait, did I already take it this week?" lives in your adherence history instead of your memory. It works for every non-daily schedule, from weekly tablets to an estradiol patch schedule that changes twice a week.
FAQ
Will taking two Fosamax tablets hurt me?
It may. Very little is absorbed: in FDA data, about 0.64% of an oral dose on average. But the label says an overdose may cause low blood calcium and phosphate and stomach or esophagus problems such as heartburn and ulcers. A published case describes a woman who took eight tablets at once, was treated in the emergency department, and was discharged after 24 hours. Stay upright, take milk or an antacid, and call your doctor or poison control (1-800-222-1222 in the US, 1-844-764-7669 in Canada).
Should I skip next week's Fosamax dose after taking an extra one?
Not on your own. The closest rule in MedlinePlus and the FDA label is the one for a missed dose, and it keeps you on one dose a week on your scheduled day. Do not skip a week to compensate unless your doctor tells you to, since MedlinePlus says not to stop taking alendronate without talking to your doctor. If your next dose falls very soon after the double-up, ask about it when you call.
What if I can't remember whether I took my Fosamax this week?
Do not take another tablet "just in case." MedlinePlus warns never to take more than one dose in one day or double up to make up for a missed one. Count your remaining pills against your last refill date, and if you are still unsure, ask your pharmacist before you take one. A medication app with a dose log removes this doubt going forward.
Why shouldn't I make myself vomit after taking too much Fosamax?
Because vomiting brings the drug back up through your esophagus, which alendronate can irritate. The FDA label states that vomiting should not be induced and the patient should remain fully upright after an overdose, due to the risk of esophageal irritation. Milk or antacids, which the label says bind alendronate, are the step to take instead.
Can I lie down if the extra Fosamax makes me feel queasy?
No. Stay sitting or standing upright. The label says the person should remain fully upright after an overdose, and lying down during or after a dose was one of the things linked to alendronate esophagus injury in a 1996 report. If queasiness turns into chest pain, new or worsening heartburn, or trouble or pain when you swallow, stop taking Fosamax and call your doctor right away.
This article provides general information about medication management and is not a substitute for professional medical advice. Consult your doctor or pharmacist for advice specific to your medications.
