The short answer

Diarrhea sits alongside nausea among the most common GLP-1 side effects, it usually clusters around dose increases, and it typically settles as your body adapts. After 65 the priority is different than at 40: it's not embarrassment — it's fluid. An older body dehydrates faster and feels it harder, and dehydration is the path from a nuisance side effect to a kidney problem. Manage the fluid and you've managed most of the risk.

For perspective from the FDA label: diarrhea led only 0.7% of Wegovy patients to stop treatment (versus 0.1% on placebo), and severe GI reactions of any kind affected 4.1% of Wegovy injection patients (versus 0.9%). Common, manageable — but not to be ignored at this age.

Why it happens

GLP-1s change the rhythm of your entire digestive tract while your gut adjusts to the medication — some people swing toward constipation, some toward loose stools, and some alternate between the two, which is disconcerting but common. Episodes tend to follow dose increases and fade over days to a couple of weeks.

Two senior-specific aggravators worth checking:

  • Sugar alcohols. Appetite shrinks, and many people lean on sugar-free products — sorbitol, mannitol, and xylitol are laxatives in disguise. Check labels on sugar-free candies, gums, and "diabetic" snacks.
  • Your other medications. Metformin famously causes diarrhea, and the combination with a GLP-1 can tip the balance. Some blood pressure medications and antibiotics contribute too. One more reason your pharmacist should review the whole list.

What helps, in order

  1. Fluids first, food second. Every loose stool is a fluid debt. Water, broth, and oral rehydration solutions (or a low-sugar electrolyte mix) beat plain water alone when episodes stack up. This is the whole ballgame after 65 — our guide to GLP-1s, dehydration, and your kidneys explains why the stakes are renal, not just comfort.
  2. Go bland and binding for a day or two. Bananas, rice, applesauce, toast, plain crackers, boiled potatoes. Skip the classic offenders while things settle: fried and fatty foods, dairy, caffeine, and alcohol.
  3. Smaller meals — the same advice that tames nausea gives the gut less to mishandle. The meal planner can build gentle, protein-forward days.
  4. Soluble fiber is your friend, roughage less so during flares — oatmeal and bananas over raw salads and bran, temporarily.
  5. Ask before taking loperamide (Imodium). It's often fine for a short episode, but in seniors it can overcorrect into days of constipation, and it should not be used with fever or blood in the stool. A quick pharmacist consult is the safe move.

And a practical note: if episodes reliably follow your injection day, tell your prescriber — sometimes the fix is as simple as staying longer at the current dose before stepping up.

When to call

  • Same-day call: diarrhea beyond about 24 hours; signs of dehydration (dark urine, dizziness on standing, dry mouth); you take diuretics ("water pills"), an ACE inhibitor/ARB, or NSAIDs — that combination plus fluid loss is hard on kidneys; or you simply cannot keep fluids down.
  • Urgent/emergency: blood in the stool, fever with severe cramping, confusion, barely urinating, or a racing heart — see the full call-the-doctor-or-911 triage guide.

Do not stop your GLP-1 on your own over a rough patch — but do report a pattern. Persistent diarrhea is a dosing conversation, not a toughness test.

Data note

Data as of August 2026; incidence and discontinuation figures per current FDA Wegovy prescribing information. Hydration guidance reflects standard geriatric practice. Blood in stool, fever, or confusion warrant urgent care. This article is educational and is not medical advice.