Maintaining proper nutrition after gastric sleeve surgery is essential for long-term health. Although the procedure primarily reduces the size of the stomach, it also alters the way certain vitamins and minerals are absorbed. These changes can increase the risk of deficiency if they are not monitored and managed carefully.
While deficiencies tend to be more common after gastric bypass, people with a gastric sleeve can still develop low levels of iron, calcium, vitamin B12 and other key nutrients. This has been our experience as well. James, for example, developed iron deficiency anaemia within his first year post-op, despite eating a balanced diet and following his supplement plan. Managing this has become part of his ongoing health routine, and regular monitoring has made a substantial difference.
The information below is based on recognised bariatric nutrition guidance and our own experience living with a sleeve. It is intended to help you understand what typically happens after surgery and how to stay on track with your long-term nutritional needs.
How Nutrient Absorption Changes After Surgery
The stomach plays an important role in digestion by producing acid and enzymes that help break down food and support nutrient absorption. After gastric sleeve surgery, the stomach is much smaller and produces significantly less acid. This reduction can make it harder for the body to absorb nutrients such as iron, vitamin B12 and calcium.
These changes are expected and do not indicate that you are doing anything wrong. They simply mean that you may need to be more intentional about food choices, supplements and follow-up appointments.
Iron
Iron is essential for producing haemoglobin, which transports oxygen around the body. Low iron levels are one of the most frequent deficiencies after bariatric surgery.
Common symptoms of low iron include:
- Tiredness or persistent fatigue
- Dizziness
- Pale skin or cold extremities
- Shortness of breath during light activity
James experienced these symptoms around 11 months post-op. Blood tests confirmed iron deficiency anaemia, and his GP explained that reduced stomach acid was limiting his ability to absorb iron from food alone.
Supporting Healthy Iron Levels
Iron-rich foods:
- Lean red meat (particularly beef)
- Poultry
- Beans, lentils and chickpeas
- Dark leafy greens such as spinach and kale
Blending greens into soups or smoothies works well if you struggle to eat them on their own.
Iron supplements:
Some people will require iron tablets or liquid iron. These should only be taken under medical guidance, and ideally not at the same time as calcium, as calcium interferes with iron absorption.
Calcium
Calcium is vital for maintaining strong bones and normal muscle and nerve function. Absorption can decrease after surgery, especially if dietary intake of dairy or fortified alternatives is low. Over time, inadequate calcium and low vitamin D levels can increase the risk of bone thinning.
Supporting Healthy Calcium Levels
Calcium-rich foods:
- Milk, yoghurt and cheese
- Kale, broccoli and other leafy greens
- Fortified plant milks (such as soy, oat or almond)
Supplements:
Calcium citrate is generally recommended for bariatric patients, as it is absorbed more effectively when stomach acid is reduced. Vitamin D3 is often prescribed alongside it to support proper absorption.
Both of us take calcium and vitamin D3 daily. It’s a simple habit that plays a major role in protecting long-term bone health.
Vitamin B12
Vitamin B12 is crucial for nerve function, red blood cell production and DNA synthesis. After gastric sleeve surgery, the stomach produces less intrinsic factor, a protein needed for B12 absorption. As a result, deficiency is common without supplementation.
Symptoms of vitamin B12 deficiency may include:
- Memory problems or difficulty concentrating
- Numbness or tingling in hands or feet
- Fatigue
- Mood changes
Supporting Healthy B12 Levels
Standard oral tablets are often not enough after a sleeve. Many people require:
- B12 injections prescribed by their GP, or
- Sublingual B12 tablets that dissolve under the tongue
Why Regular Follow-Up Appointments Matter
Nutrient levels can change over time, which is why regular blood tests remain important long after surgery. Most bariatric teams recommend testing several times during the first 18 months and annually thereafter.
Blood tests typically include:
- Iron and ferritin
- Vitamin B12
- Folate
- Vitamin D and calcium
- Liver function
- Electrolytes
Identifying issues early allows them to be corrected before they lead to long-term health problems.
How We Manage Our Nutritional Routine
Staying nourished isn’t about perfection – it’s about consistency. Here are the habits that help us stay on track:
Food tracking:
We use a simple tracker to keep an eye on protein, iron and calcium intake.
Meal preparation:
Preparing a few balanced meals in advance prevents last-minute choices that may not meet nutritional needs.
Hydration:
We aim for at least two litres of fluids a day, excluding protein shakes.
Supplement routine:
We take our supplements at set times. A structured schedule helps prevent missed doses, especially on busy days.
These habits have been crucial in keeping our energy levels stable and avoiding preventable deficiencies.
Good nutrition after gastric sleeve surgery is about supporting long-term health, not just weight loss. Deficiencies can develop gradually and may not show obvious symptoms at first, which is why proactive monitoring and a consistent supplement routine are so important.
In our experience, staying mindful of nutrients such as iron, B12 and calcium has made a significant difference to how we feel day-to-day. When your nutritional foundation is strong, your energy improves, recovery is smoother, and your overall quality of life becomes much more stable in the long run.
Disclaimer: This article is based on recognised nutritional guidance for bariatric patients and our personal experience living with gastric sleeve surgery. It is not medical advice. Always speak to your GP, bariatric team or registered dietitian before making changes to your diet or supplement plan.