Lab Work Post-Op

Why Lab Work Post-WLS Is Crucial

July 24, 2023

Why Lab Work Post-WLS Is Crucial: Bariatric surgery is a great weight loss tool. Your tool may work with different mechanism:

  • Restriction: All forms of bariatric surgery provide restriction, which means you will be eating less volume.
  • Hormonal changes: The stapling procedures, such as sleeve and bypass provide hormonal changes, meaning they decrease your appetite hormone, or may affect hormones that slow-down your stomach emptying. These hormonal effects keep you full for a longer time, and again results in less food consumption.
  • Malabsorption: Malabsorptive procedures, such as gastric bypass and duodenal switch also decrease food absorption, meaning you will absorb only a fraction of the small volume you are able to eat.

These are all helpful mechanisms, as they help you lose weight and keep it off. But they also necessitate nutritional vigilance on your part and monitoring on our part!

Your part- Nutritional vigilance:

Before your weight loss surgery, you could eat a large amount of food. Somewhere in that large volume, your body would find nutrition. The rest of that large volume would cause you weight gain.

With the decreased food volume after weight loss surgery, you have to assure nutritional value for your little meal, to maintain a good nutrition and health. Basically, you cannot waste your small stomach on food that lacks nutritional value, or your body gets in trouble.  

Another part of nutritional vigilance is working with your bariatric team do their part and monitor your nutrition and make sure you are safe and healthy.

Our part- Monitoring:

Even when you watch everything closely and follow all the rules, still the small volume, and the additional decreased absorption in malabsorptive procedures, can result in nutritional deficiencies. This is why your bariatric surgeon and their team has to fuss over your food, you taking additional vitamins and supplements, and periodically testing you, to assure you are getting what you need to maintain a healthy body.   

What do we monitor?

We routinely monitor the vitamins and minerals that are more commonly affected, such as B12, folic acid, B1, and iron. Some of these deficiencies, such as B12 deficiency, if left undiagnosed and untreated can have devastating effects on many organs. This is one of the top reasons your bariatric team puts such emphasis on your routine bariatric labs.

Since some nutritional deficiencies may cause anemia or affect your liver or kidney functions, we check all of those tests, as well.

We also monitor indicators of your bone health. This includes your levels of calcium, vitamin D, and parathyroid hormone. Patients also get their bone density checked one year after weight loss surgery, and periodically thereafter, to assure maintaining healthy and strong bones, during massive weight loss.

Furthermore, many of our patients start with diabetes, fatty liver, or abnormal lipid levels. We typically check related blood tests to monitor the improvement in those conditions, as you lose and maintain weight. More than 90% of patients see either resolution or various degrees of improvement in these problems. It is therefore important to follow these tests to guide stopping or resuming related medications.

Why Lab Work Post-WLS Is Crucial

Nutritional vigilance, routine follow-ups after your bariatric surgery, and having your labs checked are crucial in preventing complications and maximizing your success.

Make sure to:

  • Watch your food for nutritional value and eat like a pro!
  • Keep all your follow ups with your bariatric team.
  • Have your routine labs done and reviewed by your bariatric team.

Many studies show patients with regular follow ups have more success with weight loss surgery, and less complications. I believe there are several reasons for this:

  • Regular follow ups give your bariatric team an opportunity to monitor you tests as discussed above, so that they can diagnose any deficiencies as soon as they start and treat them in a timely manner.  
  • Follow ups provide patients with the essential reminders to stay on track. We are just human and are bound to forget things and fall off track.
  • Your office follow up is an opportunity to discuss even small problems, and not let them turn into big ones.
  • It is also an opportunity to monitor your weight, and stop weight regain early on. 

Fariba Dayhim, MD was one of the first bariatric surgeons in the country to get an ABOM certification. Dr. Dayhim can be reached at SSM Health.

Lab Work Post-op
Fariba Dayhim


Fariba Dayhim, MD was one of the first bariatric surgeons in the country to get an ABOM certification. Dr. Dayhim completed a minimally invasive/bariatric surgery fellowship at Texas Medical Center/The Methodist Hospital in Houston. As a bariatric surgeon, obesity medicine physician and the Medical Director of a Comprehensive Bariatric Program, she has extensive knowledge of every aspect of Bariatic Medicine. Dr. Dayhim can be reached at SSM Health.