Somewhere around month eleven, we both learned the hard way that a gastric sleeve does not stop asking things of your body once the weight loss slows down. James had spent a couple of weeks feeling generally worn out, putting it down to work and bad sleep, until a routine blood test came back showing his ferritin had dropped low enough to explain it. That was the moment blood tests stopped being a box-ticking exercise for us and started being something we actually paid attention to.
Why this does not stop being a risk after year one
It is tempting to think of the first year as the risky part, since that is when the weight loss is fastest and the diet stages are strictest. In reality, a sleeve permanently reduces how much you eat and how much your body absorbs from what you do eat, and that does not reverse itself once you reach maintenance. The British Obesity and Metabolic Surgery Society recommends at least annual monitoring of nutritional status for life after bariatric surgery, run jointly between your surgical team and your GP, precisely because the risk of running low on key nutrients never fully goes away.
What actually gets checked
For sleeve patients specifically, BOMSS guidelines call for a full blood count, urea and electrolytes, and liver function tests every year as a baseline. On top of that sits a longer list: ferritin, folate, calcium, vitamin D, parathyroid hormone, thiamine, vitamin B12, zinc and copper. The first time we saw that full list written out, it felt excessive for what we had assumed would be a quick check. It is not excessive. Each one of those markers is quietly tracking a different way the sleeve can cause a shortfall, often long before you would notice anything was wrong day to day.
James now has ferritin and B12 checked more often than the standard annual schedule, because low iron has become a repeat offender rather than a one-off. When it drops far enough, the pattern is fairly predictable: tiredness first, then lightheadedness, then genuinely fainting if he stands up too quickly, which is exactly what happened before a test caught it early enough to fix with supplementation rather than an infusion.
Getting the timing right
Most bariatric teams book bloods at three months, six months and twelve months after surgery, then move to yearly testing once things look settled. Because we had our surgery abroad, at Weight Loss Riga in Latvia, we did not have an automatic NHS recall system chasing us for appointments the way a UK-based patient might. If your surgery was overseas too, it is worth being direct with your GP early on and asking them to formally take over your monitoring schedule, rather than assuming someone else has it covered.
There are also symptoms that mean you should not wait for the calendar date to come round. Persistent fatigue that does not lift with rest, dizziness or fainting on standing, tingling in the hands or feet, hair loss beyond what is normal in the first year, and bruising that appears without explanation are all reasonable grounds to ask for bloods sooner. None of those are things to quietly push through until the next scheduled appointment.
What we actually do differently now
Two years on, blood tests are booked in advance rather than remembered at the last minute, and results get read properly rather than skimmed for a thumbs up from the GP portal. James has adjusted his iron supplementation more than once based on what a test actually showed, rather than guessing from how he felt. That shift, from reactive to scheduled, has made the biggest practical difference, because the deficiency crisis we went through at month eleven, with fatigue, brain fog and cold intolerance all landing at once, taught us that by the time you feel it, you are often already behind.
None of this works without the supplements actually being taken consistently in between appointments too. Missing a run of iron tablets is an easy thing to let slide when life gets busy, and it is exactly what has brought James’s anemia back more than once. The testing catches it, but it is the daily habit that prevents it in the first place.
Sources
British Obesity and Metabolic Surgery Society (BOMSS): Guidelines on perioperative and postoperative biochemical monitoring and micronutrient replacement for patients undergoing bariatric surgery.
NHS: information on bariatric surgery aftercare and long-term follow-up.
About this content
This blog is written by James and Kirsten, a couple from the UK who had gastric sleeve surgery together in March 2024.
We started this blog because we couldn't find any sources of content that details before surgery, the surgery and then life post surgery - so we decided to write one ourselves.
Everything on this site is based on our own experience and the research we have done along the way. It is not medical advice. Gastric sleeve surgery is a serious procedure and every patient's journey is different. Please always consult your own bariatric team or GP before making any decisions about your health or treatment.
Some posts on this site may contain featured or sponsored content, or affiliate links. Where this is the case, it will always be clearly stated at the top of the article. Our opinions are always our own.
Publish Date: 18 July 2026 | Last Reviewed: 9 August 2026 | Next Planned Review: 9 February 2028