MUST (Malnutrition Universal Screening Tool)
MUST is a five-step, validated screening tool that grades the risk of malnutrition from body mass index, unplanned weight loss and acute illness; a score of two or more means high risk and triggers a referral.
Plain English
Patient-Friendly Explanation
MUST stands for the Malnutrition Universal Screening Tool. It was developed by the British Association for Parenteral and Enteral Nutrition and it is used across hospitals, care homes and general practice to find people who are malnourished or at risk of becoming so. It takes about five minutes and has three parts. The first is body mass index, scored zero if it is above 20, one if it is between 18.5 and 20, and two if it is below 18.5, with a lower cut-off of 20 applied to older adults. The second is unplanned weight loss over the previous three to six months, scored zero for under five per cent, one for five to ten per cent, and two for more than ten per cent. The third is the effect of acute illness: if a person has eaten essentially nothing for more than five days, or is likely to, that adds two points. The three scores are added. Zero means low risk, one means medium risk and requires observation, and two or more means high risk and requires referral for assessment by a dietitian or nutrition team. The tool comes with a care plan for each score, and it has been validated thoroughly: in hospital wards, high-risk patients stay two to four times longer than low-risk patients, and the score predicts discharge destination and mortality. Two independent assessors usually reach the same score. It may seem strange to screen for malnutrition in a weight-management clinic, but there are several situations where it matters. People awaiting or recovering from bariatric surgery, those having a second operation, people on very low-calorie diets and older adults with obesity are all at risk of losing muscle and becoming undernourished while their weight is still above normal. One limitation is worth remembering: MUST is not a tool for judging obesity, because a body mass index above 30 simply scores zero.
Medical
Clinical Definition
The Malnutrition Universal Screening Tool, published by BAPEN in 2003, comprises three components scored and summed. Step 1 assigns a body mass index score of 0 for above 20 kg/m2 (including obesity), 1 for 18.5-20 kg/m2 and 2 for below 18.5 kg/m2, with a lower cut-off of 20 kg/m2 applied in adults aged 65 and over. Step 2 scores unplanned weight loss over the preceding three to six months as 0 for less than 5 per cent, 1 for 5-10 per cent and 2 for more than 10 per cent. Step 3 adds a score of 2 if the patient is acutely ill and has had, or is likely to have, no nutritional intake for more than five days. A total of 0 indicates low risk, 1 indicates medium risk with observation required, and 2 or more indicates high risk requiring referral to a dietitian or nutrition support team; a management guideline is specified for each category. Where height, weight or body mass index cannot be obtained, mid-upper arm circumference and ulna length can be used to estimate category. The tool has demonstrated face, content, concurrent and predictive validity: in medical, elderly and orthopaedic wards it predicts length of stay - up to two to four times longer in high-risk than low-risk elderly medical patients - as well as discharge destination and mortality after adjustment for age, and in the community it predicts hospital admissions and general practitioner visits. Inter-observer reproducibility is high, with kappa values between 0.8 and 1.0 across hospital, outpatient, primary care and care-home settings, and the tool is quick and acceptable to both patients and staff. Other validated instruments include the Malnutrition Screening Tool, the Mini Nutritional Assessment and the Subjective Global Assessment. Its role within weight management is to detect the patient at risk of protein-energy malnutrition or sarcopenia despite a high body mass index - particularly before and after bariatric surgery, during very-low-calorie diets, and in older adults losing weight rapidly - and it must be interpreted with the knowledge that obesity scores zero on the body mass index component.
Key Insight
Why It Matters
In a clinic focused on losing weight, the opposite risk also has to be screened for: MUST takes five minutes and identifies the person who is losing muscle or eating too little while their body mass index still looks fine.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: October 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
