Refeeding syndrome is the most dangerous acute complication of nutritional rehabilitation and the most important reason to hospitalise severely malnourished patients before commencing nutritional support — it occurs because starvation causes intracellular depletion of phosphate, potassium, and magnesium while maintaining relatively normal serum levels (electrolytes shift from cells into plasma to maintain extracellular homeostasis). When carbohydrate is introduced (stimulating insulin release), glucose and these electrolytes are rapidly transported back into cells, causing sudden severe hypophosphataemia (the most dangerous component), hypokalaemia, and hypomagnesaemia. The consequences: hypophosphataemia impairs ATP synthesis, causing cardiac arrhythmias, respiratory muscle failure, haemolytic anaemia, rhabdomyolysis, and seizures — all potentially fatal. The NICE guidelines (CG32) define high-risk patients as those with BMI below 14, or those who have eaten little or nothing for more than 5 days, or who have significant electrolyte abnormalities before feeding. For these patients, nutritional support should be commenced at 10 kcal/kg/day maximum (5 kcal/kg/day for extreme cases) with daily electrolyte monitoring for the first 72 hours.

The MUST tool is the validated, evidence-based screening instrument endorsed by NICE, BAPEN, and BAPEN for identifying malnutrition risk in community, hospital, and care home settings — it is free to use, takes approximately 5 minutes, and should be applied to all adults in primary care with: unintentional weight loss, BMI below 20, poor appetite, chronic disease associated with nutritional risk, or presentation with any condition that might impair food intake. MUST was developed and validated by BAPEN (British Association for Parenteral and Enteral Nutrition) and has been incorporated into NHS Quality Improvement frameworks. Every GP practice should be able to perform MUST scoring — the tools are available free at bapen.org.uk. The key clinical action: MUST score ≥2 = refer to dietitian without delay. The MUST calculation requires weight, height (or estimated from knee height or ulna length in patients who cannot stand), and information about recent unintentional weight loss. For patients who cannot be weighed (housebound, unable to stand): use demi-span or ulna length to estimate height, and BMI can be estimated from reported weight.

Food insecurity is a growing public health crisis in the UK that GPs encounter increasingly in primary care — the Trussell Trust reported that food bank use in the UK reached record levels in 2023-24, with approximately 3.1 million emergency food parcels distributed. Food insecurity is associated with: undernutrition, micronutrient deficiencies, obesity (paradoxically — cheap calorie-dense food is more affordable than nutritious food), and poor metabolic health (T2DM, cardiovascular disease). GPs are often the first professional to identify food insecurity in a patient — the NICE guideline on food insecurity (PH guidance, 2020) recommends that clinicians ask about food access directly: 'In the last 12 months, have you been worried whether your food would run out before you had money to buy more?' A positive answer should prompt: social prescribing referral (community navigator, food bank referral, council benefits check), assessment for benefit entitlement (PIP, UC, council tax support), and practical support (meal delivery services, WRVS community meals, Healthy Start vouchers for eligible pregnant women and young children).

The serum albumin interpretation in malnutrition requires careful clinical contextualisation — albumin is widely used as a nutritional marker but is primarily a negative acute-phase reactant: its serum level falls rapidly during inflammatory states (infection, surgery, trauma, malignancy, CKD) because the liver preferentially synthesises acute-phase proteins (CRP, fibrinogen, alpha-1-antitrypsin) at the expense of albumin production. This means a patient with well-established severe malnutrition can have a normal albumin (if not acutely unwell), while a well-nourished patient with acute sepsis can have a low albumin. The CRP:albumin ratio is a better combined marker — a high CRP with low albumin indicates inflammatory-driven hypoalbuminaemia rather than pure nutritional depletion. Prealbumin (transthyretin) has a shorter half-life (2 days vs 20 days for albumin) and is a more sensitive marker of current nutritional status — it falls earlier in malnutrition and rises more rapidly with treatment. However, it is also suppressed by inflammation and is not universally available in primary care.

The eating disorder referral pathway in adults requires specific clinical awareness — malnutrition from anorexia nervosa in adults (particularly in the 30-50 age group, where it is frequently undiagnosed) can be severe and life-threatening. The MARSIPAN (Management of Really Sick Patients with Anorexia Nervosa) guideline provides a medical risk assessment framework using physical parameters to determine whether inpatient medical admission is required before or alongside psychiatric treatment. Key medical admission thresholds: BMI below 13, heart rate below 40 bpm, BP below 80/50, QTc above 450ms, potassium below 3.0 mmol/L, or syncope. GPs suspecting eating disorder in an adult with malnutrition should: weigh the patient (with consistent clothing), measure BMI, check ECG (QTc prolongation from hypokalaemia is an arrhythmia risk), check electrolytes and glucose, and refer to the local adult eating disorder service (NHS) or liaison psychiatry if acutely medically unwell.

The oral nutritional supplement (ONS) prescribing criteria under ACBS (Advisory Committee on Borderline Substances) are specific and should be applied before prescribing — ONS are licensed for NHS prescription only when: the patient has a disease-related malnutrition state (not just preference or convenience), dietary supplementation alone has been attempted and failed or is inadequate, and the patient has a MUST score of ≥2 or a specific qualifying condition (cancer, IBD, cystic fibrosis, renal disease, etc.). The NHS drugs bill for ONS is substantial (approximately £80 million per year in primary care), and inappropriate prescribing (prescribing ONS as snacks for well-nourished patients, or without dietitian input) is an ongoing quality issue. GPs should: (1) apply MUST before prescribing ONS; (2) refer to dietitian for assessment before or alongside prescribing; (3) specify the duration of the ONS prescription and review at 4-6 weeks; (4) document the clinical indication. NICE Medicines evidence commentary (2020) recommends that ONS prescribing is supported by dietitian involvement and that prescriptions are reviewed at least every 3 months.

The PEG tube in late-stage dementia debate is one of the most ethically charged and clinically misunderstood areas of geriatric medicine — a landmark systematic review (Finucane 1999, updated 2012) found no evidence that tube feeding in patients with advanced dementia improves survival, prevents aspiration pneumonia (it may actually increase it — tube feeding does not protect against aspiration of oropharyngeal secretions), reduces pressure ulcer incidence, or improves comfort and quality of life. Despite this evidence, many families and clinicians continue to request PEG tubes for patients with advanced dementia, driven by a belief that 'not feeding' is causing the death, when in reality the dementia is causing the progressive loss of appetite and swallow function. NICE NG97 (Dementia) explicitly states that enteral tube feeding should not be routinely offered to patients with advanced dementia who are eating and drinking poorly. The GP's role: have honest conversations with families about the disease trajectory, the lack of benefit from tube feeding in advanced dementia, and the importance of focusing on comfort and dignity in eating experiences (preferred foods, warm environment, patient-centred timing).

Mirtazapine's appetite-stimulating property makes it a particularly valuable antidepressant choice in elderly malnourished depressed patients — mirtazapine antagonises alpha-2 adrenoreceptors (reducing norepinephrine negative feedback → increased norepinephrine and serotonin), H1 receptors (causing sedation and weight gain — useful in insomnia + weight loss), and 5-HT2C receptors (reducing satiety signalling → increased appetite and weight). Multiple observational studies and a Cochrane review confirm that mirtazapine causes clinically meaningful weight gain (approximately 1-2 kg over 8 weeks) and appetite improvement in depressed patients. The starting dose is 7.5-15 mg at night in elderly patients (lower doses are more sedating due to relatively greater H1 antagonism at low doses). This makes mirtazapine the antidepressant of choice when the clinical priority is: (1) depression + insomnia + weight loss in an elderly patient, or (2) depression + cancer-related anorexia (some evidence for appetite improvement in cancer cachexia independently of antidepressant effect).

The Wernicke encephalopathy emergency is one of the most important clinical scenarios in malnutrition — it occurs when thiamine (vitamin B1) deficiency impairs pyruvate dehydrogenase (the enzyme linking glycolysis to the citric acid cycle), causing accumulation of toxic metabolites in the thalamus, mammillary bodies, and periventricular areas. The clinical triad: confusion + ataxia + ophthalmoplegia (nystagmus, sixth nerve palsy, lateral gaze palsy). Not all features need to be present — in clinical practice, any patient who is malnourished (alcohol-related, prolonged vomiting, post-bariatric surgery, cancer) and presents with confusion should be assumed to have Wernicke encephalopathy until thiamine-replete. The critical safety rule: NEVER give IV glucose (dextrose) to a malnourished patient without first giving thiamine — glucose increases the metabolic demand for thiamine, and in a thiamine-depleted patient, IV dextrose can precipitate acute Wernicke encephalopathy. The emergency treatment: IV Pabrinex (high-dose B-vitamins — thiamine 250 mg in Pabrinex I+II combined given three times daily for 3-5 days), followed by oral thiamine 100 mg TDS maintenance. Always prescribe thiamine before and with any glucose administration in a malnourished patient.