August 2026

Vitamin B12 After Bariatric Surgery: What You Need to Know

Stomach acid is needed to separate B12 from food before it binds to a transporter protein called Intrinsic Factor. Gastric Sleeve and Bypass Surgery, and any other malabsorptive condition such as coeliac disease, gastrectomy, or heavy alcohol consumption, all impact B12 absorption and transport. Gastric Sleeve Surgery also removes the part of the stomach that houses the bulk of Intrinsic Factor, the protein required for B12 absorption, significantly reducing B12 absorption.

The general population requires around 4 mcg of B12 daily to stay healthy. Bariatric patients and those with malabsorptive conditions may need 350–500 mcg daily, because most of the B12 isn't absorbed.

To reach your daily requirement, you'll need a larger dose than the general population, which is quite difficult to meet through food alone. Being mindful of including B12-rich foods, alongside supplementation where your practitioner finds your levels are low, is key to maintaining healthy B12 levels

Why is Vitamin B12 so Important?

So what exactly is B12, and why does it matter so much? B12 is a water-soluble vitamin found predominantly, and in the highest amounts, in animal foods and products.

It helps us produce blood cells and DNA, and keeps our brain and nerves functioning properly. If levels become insufficient, this can affect cognitive and neurological function - another reason why maintaining adequate B12 is so important, particularly after Bariatric Surgery.

Symptoms of Vitamin B12 Deficiency

The list of symptoms of B12 deficiency is long (and, frankly, exhausting!). These symptoms have many possible causes, if you are experiencing any of them, please consult your healthcare provider for appropriate blood work and diagnosis rather than self-treating.

Fatigue
Tingling or numbness in the hands, legs, arms or feet
Weakness
Vision changes
Clumsiness, imbalance or lack of coordination
Difficulty concentrating
A smooth or 'beefy' tongue
Feeling cold all the time
Behavioural changes and low mood
Shortness of breath
Pale and/or dry skin
Memory changes — forgetting names, confusion, or brain fog

Foods With Vitamin B12

Vitamin B12 is found in animal products such as eggs, meat, fish and dairy. Factors that increase the risk of B12 deficiency include:

Following a vegan or vegetarian diet
Bariatric Surgery
Taking proton pump inhibitors for reflux
Older age
Coeliac disease
Overuse of alcohol

If you fall into one of the categories that increase your likelihood of B12 deficiency or malabsorption, it's important to check your levels with regular blood screening, and maintain healthy levels with supplements where necessary. Knowing your B12 levels are optimal is important for your overall health — regular blood screening with your healthcare team is the best way to stay on top of this.

The RDI for B12 for the general population is 1.2–2.8 mcg. It's important to note that the ASMBS recommends 350–500 mcg of B12 daily after any form of Bariatric Surgery.

Vegan Sources of B12

Nutritional yeast — 5g contains up to 7.5 mcg
Fortified plant-based milk and cereals
Fortified vegan spreads
Tempeh
Fortified meat substitutes
Certain seaweeds, such as Japanese and Korean nori

Animal-Based Sources of B12

Milk — one cup contains up to 1.1 mcg
Yoghurt — one cup contains up to 1.2 mcg
Cheese — 100g of cheddar contains up to 0.8 mcg
Eggs — a serving of 2 eggs contains up to 1.1 mcg
Kidneys and liver — 100g contains up to 72 mcg
Sardines — 150g contain up to 13 mcg
Clams — 100g contain up to 99 mcg
Beef — 100g contains up to 6 mcg
Tuna — 100g contains up to 11 mcg

Benefits of B12 Supplements

Although including animal foods in your diet should help you maintain adequate B12 levels, some people have difficulty absorbing B12 from food and may still fall short. In this case, your health practitioner may recommend a B12 supplement.

The difference between getting B12 from a supplement rather than from food is that in supplement form, B12 isn't bound to a protein, so it doesn't need stomach acid to detach it before it can be absorbed. This makes supplements a practical option for many WLS patients. Consult your healthcare professional if you think you might have low B12 levels.

Keeping up with the nutritional challenges after Bariatric Surgery can feel like a juggle. But by staying well informed about what your body needs each day, to make up for both the reduced food intake and the malabsorptive effects of Weight Loss Surgery, you'll be well equipped to stay on track.

Reaching your nutritional targets for vitamins and minerals is key, and your healthcare team is your best support for monitoring your blood and adjusting your regime to keep your levels safe and help you feel your best every day. After all, that's what the journey is all about.

Eating a broad diet made up of whole foods is a great start. Always check with your team before adding or removing any nutritional supplement.