Alendronate and Kidney Health: Safety, Risks, and Monitoring (2025)

You’re weighing bone protection against kidney safety. That’s the trade-off with alendronate. The good news: for most people with normal or mildly reduced kidney function, it’s considered safe when used properly. The catch: once kidney function drops below a certain line, it becomes a no-go and you’ll need a different plan. Here’s a clear, practical guide so you can make a confident call with your doctor.

• TL;DR: Alendronate is generally fine if your eGFR is 35 mL/min/1.73 m² or higher; below that, labels advise against it.
• Check before you start: baseline eGFR, calcium, vitamin D, and dental status; repeat kidney tests at least yearly, more often with CKD.
• Big red flag range: eGFR <30-avoid without specialist input; consider alternatives and correct calcium/vitamin D first.
• If you’re on diuretics, NSAIDs, or have dehydration risk, tighten monitoring to protect kidneys.
• IV bisphosphonates carry higher kidney risk than oral alendronate; denosumab needs strict calcium monitoring in advanced CKD.

What alendronate does and why kidneys matter

Alendronate is a bisphosphonate used to treat and prevent osteoporosis. It slows down bone breakdown, reduces fracture risk, and sticks around in bone for years. You usually take 70 mg once a week on an empty stomach with a large glass of water, then stay upright for at least 30 minutes to protect your esophagus.

Why do kidneys matter? Alendronate is not metabolised by the liver-it’s excreted unchanged by the kidneys. In healthy kidneys, that’s fine. When kidney function is reduced, the drug can accumulate, and the label draws a firm line at low creatinine clearance. The core rule used worldwide is simple: avoid in severe kidney impairment.

Here’s how regulators put it:

“FOSAMAX is not recommended for patients with creatinine clearance less than 35 mL/min. No dosage adjustment is necessary in patients with creatinine clearance 35 to 60 mL/min.” - FDA Prescribing Information (latest label revision), echoed in Australian TGA Product Information.

Real-world safety: large osteoporosis trials that included people with mild-to-moderate chronic kidney disease (CKD) didn’t show faster declines in kidney function on alendronate compared with placebo. Observational cohorts of older adults with stage 3 CKD report similar findings. The signals that do worry kidney doctors are mostly tied to intravenous bisphosphonates (like zoledronic acid), high single doses, or patients who are dehydrated or on multiple nephrotoxic drugs.

Quick note for Australians: alendronate (weekly 70 mg tablets, sometimes paired with vitamin D) is PBS-listed. Local advice from the TGA and the RACGP lines up with the global stance-fine at eGFR ≥35 with standard dosing, avoid below that, and monitor.

Kidney function ranges: what’s safe, risky, and off-limits

Most decisions hinge on your eGFR (estimated glomerular filtration rate), which you’ll see on your blood test results. Use this as a practical map you can take to your GP or specialist.

Simple decision rules you can use:

• eGFR ≥35: you can usually use alendronate at the normal dose (70 mg weekly), no adjustment needed.
• eGFR 30-34: you’re at the border. The label says avoid. If fracture risk is very high, speak with a specialist about alternatives.
• eGFR <30 or on dialysis: avoid alendronate. Treat bone health under a nephrologist’s guidance.

Who should pause or skip alendronate regardless of eGFR?

• Trouble swallowing or esophageal disorders, inability to sit or stand upright for 30 minutes, or active upper GI ulcers.
• Low blood calcium (hypocalcaemia) that hasn’t been corrected.
• Severe dental disease with planned major dental surgery (talk with your dentist first).

How kidney risk shows up and what to watch:

• New or worsening fatigue, swelling in legs, less urine than usual, or rising creatinine on blood tests-call your doctor.
• Big dehydration risk (gastro bug, hot weather, fasting, heavy exercise) can tip borderline kidneys over. Keep fluids up and check meds.
• Other nephrotoxic hits at the same time-NSAIDs (like ibuprofen), high-dose diuretics, contrast dye-raise risk.

What the evidence says (in plain English): People with CKD stage 1-3 on alendronate don’t seem to lose kidney function faster than similar people not taking it. This comes from pooled phase 3 trials and large observational studies of older adults. Intravenous bisphosphonates are the ones linked to acute kidney injury, especially zoledronic acid in the frail, dehydrated, or those with prior kidney disease.

Regulatory and guideline anchors you can trust: FDA and TGA labels set the 35 mL/min cutoff; KDIGO 2024 CKD guidance supports treating osteoporosis in CKD with attention to eGFR and mineral metabolism; RACGP/Endocrine Society guidance aligns on monitoring calcium, vitamin D, and renal function while balancing fracture risk.

Practical plan: monitoring, side effects, and alternatives if alendronate isn’t right

This is the game plan I give patients in clinic. It keeps kidneys front and centre while you protect your bones.

Before you start (or continue) alendronate:

• Repeat kidney bloods: urea, creatinine, eGFR. If you’re new to CKD or on diuretics, set a reminder for a recheck in 3 months.
• Check calcium, phosphate, and vitamin D. Correct low calcium or vitamin D first.
• List your meds: NSAIDs, loop/thiazide diuretics, ACE inhibitors/ARBs, SGLT2 inhibitors, metformin-bring this list to the appointment. Your GP may tweak timing or doses.
• Dental check if you have poor teeth, dentures that rub, or planned extractions. Good mouth care lowers the small osteonecrosis risk.
• Fracture risk calc: ask for a FRAX or Garvan score. If risk is low, you might not need a drug at all.

How to take it safely:

1. First thing in the morning, empty stomach.
2. Take the tablet with a full glass (at least 200 mL) of plain water-no coffee, juice, or mineral water.
3. Stay upright (sitting or standing) for 30 minutes, and don’t eat or drink anything else in that time.
4. If you miss the weekly dose, take it the next morning; don’t double up later in the day.

Kidney-protective habits that matter:

• Hydration: on hot Brisbane days or when you’re sick with vomiting/diarrhoea, fluids first. If you can’t keep fluids down, ring your GP.
• Think before NSAIDs: reach for paracetamol for pain unless your doctor says otherwise; many CKD plans avoid regular NSAIDs.
• Sick day rules: if you get gastro or a fever, ask your GP which meds to pause temporarily (often diuretics or ACE/ARBs-not alendronate).
• Lab cadence: annually if eGFR ≥60; every 6-12 months if 45-59; every 3-6 months if 30-44; sooner after any dehydration or med changes.

Side effects: what’s common vs what needs action

• Common: heartburn, stomach upset, muscle/joint aches. Usually settle or can be managed with timing adjustments.
• Uncommon but urgent: chest pain or trouble swallowing (stop and seek care), new severe bone or thigh pain (rule out atypical fracture), jaw pain after dental work (rare osteonecrosis-call your dentist/doctor).
• Kidney-specific: a rise in creatinine is uncommon with oral alendronate; if it happens, your doctor will look for dehydration, NSAID use, or other causes first.

What if your eGFR is too low for alendronate?

• Denosumab (Prolia): not cleared by kidneys, so fracture reduction holds at any eGFR, including dialysis. The catch is severe hypocalcaemia risk in advanced CKD. You must correct low calcium/vitamin D first, check calcium within 10-14 days after the first dose, and keep monitoring. The FDA added boxed warnings in 2024 about this in advanced CKD; Australian guidance mirrors this caution.
• Raloxifene: selective estrogen receptor modulator. Lower vertebral fracture risk only; minimal kidney concerns, but raises clot risk. Fits some postmenopausal women with lower overall risk.
• Teriparatide/abaloparatide: bone-building agents. Can be considered in CKD with specialist oversight; watch for hypercalcaemia and avoid in certain metabolic bone states. Often used for very high fracture risk or after atypical fractures.
• Zoledronic acid (IV): effective for bones but carries the highest kidney injury signal among bisphosphonates. Avoid in low eGFR and in anyone dehydrated or on multiple nephrotoxins.

Lifestyle moves that help both bones and kidneys:

• Calcium from food first (dairy, fortified milk alternatives, tofu with calcium, leafy greens). In CKD, avoid high-dose calcium supplements unless advised-there’s a balance to strike.
• Vitamin D: safe sun or supplements as guided by bloods; CKD can alter vitamin D handling, so test rather than guess.
• Strength and balance work: squats to a chair, heel raises, tai chi or yoga; aim 2-3 sessions a week. Falls cause fractures more than low density alone.
• Quit smoking, moderate alcohol, manage blood pressure, and keep diabetes steady-these slow kidney decline and help bones.

Quick checklist to take to your next appointment:

• My latest eGFR is: ____ (date: ____)
• Any recent dehydration illness? Yes/No
• Regular NSAID use? Yes/No
• On diuretics or ACE/ARB? List: ____
• Calcium: ____ Vitamin D: ____ (attach lab printout)
• Dental plan in the next 3 months? Yes/No
• FRAX/Garvan fracture risk score: ____

Mini-FAQ

• Do I need a lower dose if my kidneys are a bit reduced? No. Labels say no dose adjustment for creatinine clearance 35-60 mL/min. The decision is to use it or not, not to halve it.
• Can alendronate cause acute kidney injury? It’s rare with oral alendronate at osteoporosis doses. Most kidney injury cases involve IV formulations, dehydration, or other nephrotoxins.
• My eGFR bounces between 33 and 38. What now? Treat the trend and the whole picture. Many clinicians avoid alendronate if it often dips below 35. Consider alternatives and repeat tests after hydration or medication review.
• Is monthly risedronate any safer on kidneys? Oral risedronate has a similar renal profile to alendronate and the same caution below eGFR ~30-35. It’s not a kidney “workaround.”
• What about stopping after five years? A “drug holiday” is often considered after 3-5 years if fracture risk becomes low-to-moderate and kidneys are stable. High-risk patients usually continue or switch therapy.

Next steps by scenario

• eGFR ≥60, high fracture risk: Start or continue alendronate, set up annual kidney labs, and add strength/balance training.
• eGFR 45-59 with multiple meds: Proceed but review NSAIDs and diuretics; plan kidney labs at 6-12 months.
• eGFR 30-44: Discuss with GP/nephrologist. If you start, lock in 3-6 month labs and watch hydration. Many will choose an alternative.
• eGFR <30 or dialysis: Don’t use alendronate. Refer to nephrology for a CKD-mineral bone disorder plan; consider denosumab with tight calcium monitoring or an anabolic agent if appropriate.
• Recent AKI, contrast scan, or gastro: Delay a new start until you’re euvolemic and kidney numbers settle.

Bottom line: if your kidneys are healthy or only mildly reduced, alendronate and kidney health can coexist just fine-use it right, monitor, and mind hydration. If your eGFR is near or under 35, press pause and get a tailored plan. This is one of those times where a 10-minute chat with your GP or nephrologist saves you a lot of guesswork and protects both bones and kidneys.