Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Refer appropriately for metabolic surgery, recognise early and late complications, and deliver lifelong procedure-specific nutritional, reproductive and medicine follow-up without losing shared-care ownership.
Metabolic surgery is the most effective durable treatment for many people with severe obesity and can improve diabetes, sleep apnoea, blood pressure, mobility and quality of life. Referral does not commit a person to an operation: a multidisciplinary assessment considers nutrition, eating behaviour, mental health, anaesthetic risk, previous treatment, capacity to follow supplementation and the procedure most likely to balance benefit and harm.
Anatomy predicts complications. Sleeve gastrectomy restricts gastric volume and alters hormones but can worsen reflux. Roux-en-Y bypass creates a small pouch and bypasses proximal bowel, increasing dumping, internal hernia, marginal ulcer and several nutrient deficiencies. Gastric bands can slip, erode or become over-tight. Duodenal-switch-type procedures carry substantial protein and fat-soluble vitamin risk and usually need enduring specialist oversight.
Follow-up is a lifelong safety intervention. Deficiencies may appear years after the original operation, when the surgeon and patient have moved. A coded register, annual recall, the operative report and a clear supplement plan prevent anaemia, neuropathy, bone disease and protein malnutrition. Unintentional loss, regain and psychological distress all deserve active assessment rather than praise or blame based only on the scale.
Intermittent or severe postprandial abdominal pain, vomiting, tachycardia or obstruction years after bypass can reflect an internal hernia; examination may be deceptively soft and CT does not always exclude it.
Poor intake or vomiting with confusion, ataxia, nystagmus, ophthalmoplegia, neuropathy, oedema or cardiac failure suggests beriberi or Wernicke encephalopathy and requires immediate treatment.
Fatigue, breathlessness, glossitis, neuropathy or cytopenias can arise from iron, B12, folate or copper deficiency; mixed deficiencies may hide the expected mean-cell-volume pattern.
Oedema, muscle loss, weakness, hair loss and low albumin after a malabsorptive operation suggest inadequate intake, vomiting, diarrhoea or excessive malabsorption and need specialist dietetic review.
Early post-meal flushing, palpitations, cramping and diarrhoea reflect rapid osmotic and hormonal effects; symptoms one to three hours later with neuroglycopenia suggest post-bariatric hypoglycaemia.
Food sticking, progressive dysphagia, repeated regurgitation or inability to tolerate protein can indicate stricture, band over-restriction or ulceration and must not be dismissed as poor eating technique.
Fear of food, recurrent bingeing, alcohol misuse, body-image distress, depression or suicidality can emerge after surgery; acute mental-health or safeguarding risk needs immediate action.
Requirements differ by procedure, sex, pregnancy and laboratory results. Avoid retinol-containing vitamin A in pregnancy, prevent duplicate high doses and never assume a multivitamin replaces separate calcium, iron or B12.
Do not wait for test results and give before glucose or carbohydrate where feasible. Neurological signs require same-day medical, neurology and bariatric review; oral absorption is unreliable during persistent vomiting.
A bypass performed fifteen years ago still changes internal-herniation risk, medicine absorption and micronutrient requirements even when the patient no longer attends surgery clinic.
Microcytic iron deficiency and macrocytic B12 or folate deficiency can cancel numerically, leaving serious mixed nutritional anaemia with an apparently normal index.
Body stores are limited and neurological injury can become irreversible; clinical risk is sufficient to treat before laboratory confirmation.
Pain may come and go and early imaging can be non-diagnostic. A bypass history plus persistent clinical concern deserves direct bariatric surgical judgement.
An ordinary multivitamin may omit enough thiamine, copper or iron for postoperative needs, while combining products can also create vitamin A or mineral excess.
Treating recurrent vomiting as an expected method of maintaining weight loss.
Waiting for thiamine levels before giving replacement in a high-risk patient.
Assuming normal serum calcium excludes bone-mineral depletion.
Using MCV alone to rule out mixed nutritional deficiency.
Discharging from surgical care without a named annual-recall owner.
Prescribing NSAIDs or modified-release drugs without considering altered anatomy.
Ignoring severe abdominal pain because surgery was many years earlier.
Continuing retinol-containing supplements during pregnancy without specialist review.
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A patient three months after gastric bypass has prolonged vomiting, unsteady gait and confusion. What is the most important immediate nutritional treatment?
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes
Do not delay treatment for neurological deficiency while awaiting every result. Folate can improve anaemia while B12 neuropathy progresses, so assess both and investigate unexpected non-response.
Calcium citrate may be preferred in selected procedures; separate calcium from iron, monitor calcium, vitamin D, PTH and renal stone risk, and avoid unmonitored loading in renal disease.