Bariatric Surgery: The Complete Guide
Preparing for Bariatric Surgery: Pre-Op Diet and Required Tests
Reviewed by the JordanMedHub Medical Editorial Team · 8/30/2026
Once you're approved for surgery, preparation typically involves a short pre-op diet and a round of medical testing — both aimed at making the operation as safe as possible.
The Liver-Shrinking Diet
In the one to two weeks before surgery, most patients follow a low-calorie, high-protein diet designed to shrink the liver. A larger liver can make laparoscopic access to the stomach more difficult and risky, so this step genuinely matters for surgical safety — it isn't just a formality.
Standard Pre-Op Testing
Established medical practice
A typical pre-op workup includes a [complete blood count](/lab-tests/complete-blood-count), [fasting blood sugar](/lab-tests/fasting-blood-sugar) and [HbA1c](/lab-tests/hba1c), [lipid profile](/lab-tests/lipid-profile), [liver function test](/lab-tests/liver-function-test), [kidney function test](/lab-tests/kidney-function-test), [thyroid function test](/lab-tests/thyroid-function-test), and [vitamin D test](/lab-tests/vitamin-d-test), alongside a cardiovascular and pulmonary risk assessment. Your surgical team will tell you exactly which tests apply to your case.
Why This Matters Beyond the Operation Itself
These same baseline results also become the starting point for your lifelong post-surgery monitoring — see our [vitamins and supplements after surgery](/articles/bariatric-surgery-vitamins-and-supplements) guide for what continues afterward.
What to Expect on Surgery Day
Most procedures are performed laparoscopically under general anesthesia, with a hospital stay of one to two nights for most patients — see the [complete guide](/articles/bariatric-surgery) for the bigger picture.
Disclaimer
Exact pre-op requirements vary by surgical team and individual health status — always follow your own surgeon's specific instructions over any general list.
Frequently Asked Questions
How strict is the liver-shrinking diet?
It's typically a structured low-calorie, high-protein diet for one to two weeks, and your surgical team will give you exact instructions — deviating from it can genuinely affect surgical safety, so it's worth taking seriously.
Will I need a psychological or nutritional evaluation as part of pre-op prep?
Most programs include these as part of the broader candidacy evaluation, generally before this specific pre-op prep stage — see our candidacy guide for details.
This article is for general health information and does not replace professional medical advice.