Procedure prep
Fasting Before Bariatric (Weight-Loss) Surgery
Bariatric (weight-loss) surgery — such as a gastric sleeve or gastric bypass — is keyhole surgery done under general anesthesia. Preparation is a bit more involved than for other operations because of the pre-op diet, GLP-1 medicines, and sleep apnea.
Fasting for this procedure
→ Get your exact fasting times with the calculator
Medicines to check
- GLP-1 medicines (Ozempic, Wegovy, Mounjaro) — very common before weight-loss surgery, and they slow stomach emptying, which matters for anesthesia safety. Do not stop on your own — your team will give a specific plan (they may pause the weekly dose or extend your clear-liquid fast). Tell them you take one. See the GLP-1 guide.
- Diabetes medicines & insulin — doses usually change with the pre-op diet; get a clear plan. See diabetes tablets.
- Blood thinners and aspirin — see medications to stop; clot prevention is important after bariatric surgery.
- Blood pressure and reflux medicines — confirm which to take with a sip of water.
When this surgery may be delayed
- Fever, a new cough/cold, or a chest infection
- Vomiting or diarrhea
- Very high blood pressure or blood sugar
- You ate or drank outside your fasting window
- You didn't complete the pre-op liver-shrinking diet
- Untreated or newly suspected sleep apnea your team doesn't know about
Reports & documents to carry
- Photo ID and insurance card
- A written list of all your medicines and doses
- Any blood tests, ECG, or scans your team asked for
- Consent forms or referral letters, and allergy details
- Your CPAP machine and mask if you use one for sleep apnea — bring it to hospital
- Details of your pre-op diet and program instructions
What to ask your anesthesia team
- Will I have general anesthesia, spinal/regional, or sedation?
- Which medicines do I take or hold on the morning of surgery?
- When can I eat and drink afterward?
- Will I go home the same day, and who can drive me?
- Exactly how do I manage my GLP-1 (Ozempic/Wegovy/Mounjaro) before surgery?
- How do I adjust diabetes medicines during the pre-op diet?
- Should I bring my CPAP, and what about my sleep apnea?
Your prep checklist
Tick things off as you sort them — saved on this device only, nothing is sent anywhere.
A general guide — your hospital's own instructions always come first.
Frequently asked questions
What do I do with Ozempic or Wegovy before bariatric surgery?
GLP-1 medicines slow stomach emptying, which raises the risk of stomach contents during anesthesia. Many patients are asked to pause the weekly dose before surgery or follow an extended clear-liquid fast — but this is individualized. Don't stop on your own; ask your bariatric and anesthesia team for your exact plan, and tell them you take one.
Why is there a special diet before weight-loss surgery?
A 1–2 week low-calorie 'liver-shrinking' diet reduces the size of the liver, which makes keyhole bariatric surgery safer and easier. It's separate from day-of fasting — follow both as instructed.
Why does my sleep apnea matter for bariatric surgery?
Sleep apnea is common before weight-loss surgery and affects how anesthesia and breathing are managed. Bring your CPAP machine to hospital, and tell your team about snoring, pauses in breathing, or daytime sleepiness even if you've never been diagnosed.