The Malnutrition Universal Screening Tool (MUST) is a five-step screening tool that identifies adults who are malnourished, at risk of malnutrition, or at low risk. You use it by measuring body mass index, tracking unplanned weight loss, and noting whether acute illness has prevented eating for more than five days. Each step produces a score, and the total score places the person into one of three care pathways: low, medium, or high risk.
MUST was developed by the British Association for Parenteral and Enteral Nutrition (BAPEN) and is widely used in hospitals, care homes, and community settings in the UK and elsewhere. It is a screening tool, not a diagnostic one. It flags who needs a closer look and a care plan. It does not by itself diagnose malnutrition.
What Is the Malnutrition Universal Screening Tool?
MUST is a validated screening instrument for adults. It was designed to be quick, practical, and usable by any trained staff member, not just dietitians.
The tool rests on three measurable inputs: current body mass index (BMI), the percentage of unplanned weight lost over the past three to six months, and the effect of acute disease on food intake. Each input is scored, and the three scores are added together.
The result is a single number from 0 to 6 or more. That number maps to a risk category and a recommended course of action. The whole process typically takes a few minutes once height and weight are known.
One point often missed: MUST is for adults aged 18 and over. It is not validated for children, and separate tools exist for pediatric populations. It is also not designed for pregnant women in the same way, because BMI interpretation changes during pregnancy.
How Do You Complete Steps 1 to 3 of MUST?
The scoring section has three steps. Each produces a number, and accuracy at this stage determines whether the final score means anything.
Step 1: Body Mass Index Score
Measure height and weight, then calculate BMI. The scoring is straightforward:
- BMI above 20 kg/m² scores 0
- BMI 18.5 to 20 kg/m² scores 1
- BMI below 18.5 kg/m² scores 2
If height cannot be measured, MUST allows for self-reported height or a proxy measure such as ulnar length or knee height. These alternatives exist because bedbound or unsteady patients often cannot stand for a stadiometer. Using them is part of the tool’s design, not a workaround.
Step 2: Unplanned Weight Loss Score
Ask about weight loss over the past three to six months, and express it as a percentage of previous body weight:
- Less than 5% lost scores 0
- 5% to 10% lost scores 1
- More than 10% lost scores 2
The word “unplanned” matters here. Intentional weight loss, such as from a deliberate diet, is not scored the same way. The question is whether the person lost weight without trying.
If the person cannot recall their previous weight, MUST allows for clinical judgment. Document what you used and why, because the score depends on it.
Step 3: Acute Disease Effect Score
This step asks a single question: is the person acutely ill and has their food intake been, or is it likely to be, zero for more than five days?
If yes, score 2. If no, score 0. There is no middle value.
This step is often the one people skip or misunderstand. It is not about appetite in general. It is specifically about acute illness or surgery that has stopped or is expected to stop oral intake for more than five days.
How Do You Calculate and Interpret the Total Score?
Add the three scores together. The total determines the risk category and the recommended action.
| Total Score | Risk Category | Recommended Action |
|---|---|---|
| 0 | Low risk | Routine clinical care; repeat screening per local policy (often weekly in hospitals, monthly or annually in community settings) |
| 1 | Medium risk | Observe; document dietary intake for three days; repeat screening per local policy |
| 2 or more | High risk | Refer to dietitian or nutritional support team; set goals and monitor |
A score of 2 or more triggers referral. That referral is not a diagnosis of malnutrition. It means the person warrants a fuller nutritional assessment and likely a care plan.
Some local protocols add a fourth “very high risk” band for scores of 6 or above, but the core MUST framework uses the three categories above. Follow whichever version your organization has adopted, and be consistent.
How Should You Handle Special Situations and Missing Measurements?
Real-world screening rarely happens under ideal conditions. MUST anticipates this.
If the patient cannot be weighed, use a chair scale, bed scale, or hoist scale. If none are available, self-reported weight or mid-upper arm circumference can substitute, with the limitation documented. The tool’s guidance explicitly allows for these alternatives because the alternative — not screening at all — is worse.
For people with fluid overload, such as those with heart failure or edema, BMI can overstate lean mass. A high BMI in a person with significant fluid retention does not rule out malnutrition. Clinical judgment and additional assessment are needed. MUST scores are a starting point, not a final answer.
For people with amputations or limb differences, standard BMI calculations are inaccurate. Adjusted formulas exist, and local protocols should specify which to use. If none does, document the limitation.
For people in acute hospital settings, screening is typically done on admission and repeated weekly. In care homes and community settings, the interval is usually longer and set by local policy. No single national interval applies everywhere.
What Are the Common Mistakes When Using MUST?
Most errors happen at the measurement stage, not the scoring stage. The arithmetic is simple. Getting accurate inputs is not.
- Estimating weight instead of measuring it. A guess can shift the BMI category and change the total score.
- Confusing intentional and unplanned weight loss. The tool asks specifically about unplanned loss.
- Skipping Step 3. The acute disease effect is easy to overlook because it requires asking about illness and intake, not just stepping on a scale.
- Treating a low score as permanent clearance. Risk changes. A person who scores 0 today can score higher after illness, surgery, or a change in appetite.
- Using MUST for children or pregnant women. The tool is validated for adults. Other tools apply to those groups.
A less obvious point: MUST was never designed to replace clinical judgment. It is a triage step. A score of 0 in someone who looks unwell or reports poor intake still deserves a clinician’s attention. The tool flags risk; it does not rule it out.
What Happens After a High MUST Score?
A score of 2 or more leads to referral, and referral leads to a fuller assessment. That assessment usually covers dietary intake, ability to eat and swallow, medical and social factors, and whether the person can meet their nutritional needs orally.
From there, a care plan is set. It may include food fortification, oral nutritional supplements, assistance with eating, or, in some cases, artificial nutrition. The choice depends on the individual, their condition, and their preferences.
MUST itself does not specify which intervention to use. It identifies who needs one. The evidence base for specific interventions is separate, and it varies by setting and population. Some approaches, such as oral nutritional supplements in malnourished older adults, have more supporting evidence than others. Others are used in practice with less trial support. That distinction matters when discussing what happens next.
What MUST does well is standardize who gets looked at. Before tools like this, malnutrition in hospitals and care homes was frequently missed. Screening changed that by making the question routine rather than reactive.
Frequently Asked Questions
Who can use the MUST screening tool?
Any trained staff member can use MUST, including nurses, care assistants, and community workers. It was designed for use by non-specialists, with referral to a dietitian for anyone scoring 2 or more.
What score on MUST means malnutrition?
MUST does not diagnose malnutrition; it identifies risk. A score of 2 or more indicates high risk and triggers referral for a fuller nutritional assessment, which is where diagnosis is made.
How often should MUST be repeated?
The interval depends on the setting and local policy. Hospitals typically repeat screening weekly, while care homes and community settings often use longer intervals set by their own protocols.
Can MUST be used for children or pregnant women?
No. MUST is validated for adults aged 18 and over. Separate tools and approaches apply to children and to pregnant women, whose BMI interpretation differs.
