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Common Nutritional Deficiencies After Bariatric Surgery

Array of healthy, nutritious food on wooden tray and counter top

One of the most problematic complications we see after bariatric surgery revolves around patients who do not meet their nutritional requirements. Patients lose weight because of a significantly restricted caloric intake, meaning they will be ingesting and using fewer vitamins and minerals. Levels of specific vitamins and minerals are more affected than others. As such, patients must work with their practice to create a supplementation plan based on the procedure performed and the results of their blood panels taken periodically after surgery.

Vitamin supplementation seems like the easiest part of the postoperative bariatric life because it requires nothing more than remembering to take supplements. However, sadly, some patients do not or cannot comply either because of the cost of supplements or because they don’t fully understand how vital supplementation is. As a result, they may experience significant and sometimes permanent side effects from their nutritional deficiency.

So, Which Vitamins and Minerals Are Commonly Prescribed to Patients After Bariatric Surgery?

Before we dive in, it’s worth mentioning that a multivitamin is always a part of a patient’s postoperative diet, regardless of the procedure performed. These multivitamins lay a foundation of supplementation to ensure that every patient receives at least the most essential nutritional requirements. These should be bariatric-specific or high-quality products that meet or exceed recommendations for bariatric patients. Other common supplements include:

Vitamin B12

Because intrinsic factor production in the stomach is compromised after virtually any bariatric procedure, vitamin B12 is not metabolized the same way. As such, B12 is a common deficiency that can compromise the function of the nervous system. Patients often take Vitamin B12 supplements daily via the oral route. However, some patients choose to receive B12 injections.

Vitamin D

Adequate vitamin D levels are also crucial to a patient’s postoperative life. In fact, without vitamin D, calcium cannot be absorbed. Most Americans, not just bariatric patients, do not get enough vitamin D daily. This is typically absorbed through the sun, but in modern-day life, we often don’t get the sun exposure needed to keep levels where they should be. Most patients will, therefore, supplement with a vitamin D3 pill.


Calcium is the building block of bone strength and works with vitamin D. Most patients can enjoy their calcium as a delicious-tasting chew, while others prefer a swallowable pill. No matter what form of calcium is taken, Patients must prioritize their intake to ensure continued bone health.


Anemia from iron deficiency can also occur. Anemia can reduce red blood cells’ oxygen and cause fatigue and other severe symptoms. Iron deficiency is more common in women than men and can be easily rectified with supplementation. Patients should follow their iron supplementation regimen closely, as iron supplements are toxic at high levels.

We will also supplement your diet based on your blood test results. This is why we encourage you to visit us as suggested in your post-op packet for follow-up care. If you move out of town and can no longer see us, you must speak to your new primary care physician and medical team to ensure you keep up with your blood work and supplementation needs. It is important also to remember that your body does change over time, and your supplementation needs will, too. These regular and periodic checkups can help you optimize your supplement intake for ideal health.

Non-essential Supplements

You may have heard of the benefits of several other optional supplements for which you do not have a deficiency. Supplements like omega-3 fatty acids (fish oil), magnesium, turmeric, and more may all have some proven or unproven benefits. Speaking to your medical team about these supplements is vital to understand if they may be right for you. It is also critical that you remember that the FDA does not regulate supplements, and their purity and potency are not guaranteed. To reduce the likelihood of problems with your supplements, be sure to choose well-established companies, preferably those that have had their products tested by reputable third-party labs.

The bottom line is that supplementation is critical to a successful post-operative bariatric life. One way to ensure that your levels are appropriate is to visit us as per your postoperative scheduled visits, where we will perform diagnostic testing to ensure you are on the right track. In the meantime, if you have any questions about your postoperative supplementation regimen, we encourage you to speak to our dietitian to get and stay on track.