MUST Calculator (Malnutrition Universal Screening Tool)

The UK standard screening tool for identifying adults at risk of malnutrition. Developed by BAPEN and used throughout the NHS.

Important Disclaimer: This calculator is for informational purposes only and should be used by qualified healthcare professionals. MUST screening should be followed by appropriate clinical assessment and intervention. Always follow your local nutrition protocols and BAPEN guidelines.
Patient Assessment
Step 1: BMI Score
BMI scoring: BMI >20 (>30 Obese) = 0, BMI 18.5-20 = 1, BMI <18.5 = 2
Step 2: Weight Loss Score (unplanned weight loss in past 3-6 months)
Step 3: Acute Disease Effect Score
Is patient acutely ill AND has been or is likely to be no nutritional intake for >5 days?
About MUST

The Malnutrition Universal Screening Tool (MUST) was developed by the British Association for Parenteral and Enteral Nutrition (BAPEN) and is the most widely used nutritional screening tool in the UK.

MUST has been validated across healthcare settings and:

  • Identifies adults who are malnourished or at risk of malnutrition
  • Includes management guidelines for developing care plans
  • Is quick and easy to use with 'weighable' and 'non-weighable' patients
  • Is recommended by NICE and part of Care Quality Commission inspections

MUST combines:

  • Body Mass Index (BMI)
  • Unintentional weight loss
  • Acute disease effect

The tool should be completed on initial assessment and repeated according to risk level, or when clinical condition changes.

MUST Risk Categories and Management

MUST Score Risk Category Management Guidelines
0 Low Risk
  • Routine clinical care
  • Repeat screening:
    • Hospital: weekly
    • Care homes: monthly
    • Community: annually for special groups (e.g., those >75 years)
1 Medium Risk
  • Document dietary intake for 3 days
  • If adequate: little concern; repeat screening:
    • Hospital: weekly
    • Care home: at least monthly
    • Community: at least every 2-3 months
  • If inadequate: clinical concern; follow local policy, set goals, improve and increase overall nutritional intake, monitor and review care plan regularly
2 or more High Risk
  • Refer to dietitian, Nutritional Support Team, or implement local policy
  • Set goals, improve and increase overall nutritional intake
  • Consider:
    • Food fortification
    • Oral nutritional supplements
    • Enteral or parenteral nutrition support (if appropriate)
  • Monitor and review care plan:
    • Hospital: weekly
    • Care home: monthly
    • Community: monthly

Alternative Measurements When Height or Weight Cannot Be Obtained

Alternative Measurements for Height

If height cannot be measured, use one of these alternatives:

  1. Ulna length: Measure from the point of the elbow (olecranon process) to the midpoint of the prominent bone of the wrist (styloid process). Use reference tables to convert to height.
  2. Knee height: Measure from the heel to the anterior surface of the thigh above the knee with the ankle and knee each flexed to a 90° angle.
  3. Demispan: Measure from the middle of the sternal notch to the finger web between middle and ring fingers with arm outstretched horizontally.
  4. Self-reported height: Use with caution, especially in elderly patients who may report their maximum adult height.

These measurements can be converted to height using published equations or reference tables available in the BAPEN MUST Explanatory Booklet.

Alternative Assessment Methods

When weight and height cannot be obtained:

  1. BMI estimation: Use subjective criteria based on visual appearance:
    • BMI <18.5 kg/m² = Very thin
    • BMI 18.5-20 kg/m² = Thin
    • BMI >20 kg/m² = Acceptable weight
  2. Acute disease effect: Ask about recent food intake and likelihood of no nutritional intake for >5 days.
  3. Weight loss estimation: Use patient records, information from relatives, or changes in clothing size.
  4. Mid-upper arm circumference (MUAC): Can be used as a surrogate for BMI:
    • MUAC <23.5 cm roughly corresponds to BMI <20 kg/m²
    • MUAC ≥23.5 cm roughly corresponds to BMI ≥20 kg/m²

FAQs about MUST

Frequency of MUST rescreening depends on the care setting and risk level:

  • Hospital settings:
    • Weekly (all patients regardless of risk)
    • More frequently if clinical concern
  • Care homes:
    • Low risk: monthly
    • Medium risk: at least monthly
    • High risk: monthly, after implementing care plan
  • Community:
    • Low risk: annually (or when clinical concern)
    • Medium risk: every 2-3 months
    • High risk: monthly

Rescreening should also occur when there is a change in clinical condition or treatment that may affect nutritional status.

Pregnant women:

MUST is not validated for use in pregnancy. Nutritional screening in pregnancy typically uses different parameters specific to maternal and fetal needs. Use guidance from NICE or the Royal College of Obstetricians and Gynaecologists instead.

Patients with fluid retention (oedema/ascites):

  • BMI and weight loss calculations may be affected by fluid retention, leading to an underestimation of malnutrition risk
  • For patients with oedema, try to obtain fluid-free weight if available (post-dialysis weight for renal patients)
  • If fluid-free weight is unavailable, clinicians should:
    • Use subjective criteria for BMI estimation
    • Look for other signs of malnutrition (muscle wasting, ill-fitting clothes)
    • Consider the presence of oedema itself as a potential indicator of malnutrition (particularly in children and some adults)
    • Focus more on the acute disease effect and recent dietary intake

Clinical judgement is particularly important when applying MUST to patients with fluid retention.

MUST compared to other commonly used nutritional screening tools:

MUST vs. Nutritional Risk Screening 2002 (NRS-2002):

  • NRS-2002 includes age as a risk factor (>70 years adds a point)
  • NRS-2002 uses more detailed disease effect grading
  • MUST is generally simpler and faster to complete
  • NRS-2002 is often preferred in acute hospital settings

MUST vs. Mini Nutritional Assessment (MNA):

  • MNA was specifically designed for elderly patients (>65 years)
  • MNA includes functional and psychological parameters
  • MNA is more detailed (18 items in full version, 6 in short form)
  • MUST is quicker and applicable across all adult age groups

MUST vs. Subjective Global Assessment (SGA):

  • SGA is more comprehensive, including physical examination
  • SGA requires more training to administer correctly
  • MUST is more focused on objective measures
  • SGA is often used as a more detailed assessment after screening

MUST has been validated across care settings (hospital, community, care homes) and is the standard in UK healthcare, making it particularly useful for consistent assessment across care transitions.

While MUST is widely used and validated, it has several limitations:

  • BMI limitations: May not be appropriate for some patient groups:
    • Athletes or highly muscular individuals (falsely high BMI)
    • Amputees or patients with skeletal deformities
    • Patients with fluid retention or dehydration
  • Specific populations: Not validated for:
    • Pregnant or breastfeeding women
    • Children and adolescents (under 18 years)
    • People with eating disorders (requires specialized assessment)
  • Acute disease effect:
    • Binary scoring may oversimplify complex clinical situations
    • Does not capture gradients of acute illness severity
  • Practical challenges:
    • Relies on accurate weight and height measurements
    • Requires knowledge of previous weights which may not be available
    • Alternative measurements require additional training
  • Limited parameters:
    • Does not assess functional status or muscle mass
    • Does not consider micronutrient deficiencies
    • No evaluation of dietary intake quality or patterns

For comprehensive nutritional assessment, MUST should be followed by more detailed assessment (especially for high-risk patients) and should always be used with clinical judgment.

References

  1. BAPEN. (2003, revised 2011). Malnutrition Universal Screening Tool.
  2. NICE. (2017). Nutrition support in adults: Quality standard [QS24].
  3. Stratton, R.J., Hackston, A., Longmore, D., Dixon, R., Price, S., Stroud, M., King, C., & Elia, M. (2004). Malnutrition in hospital outpatients and inpatients: prevalence, concurrent validity and ease of use of the 'malnutrition universal screening tool' ('MUST') for adults. British Journal of Nutrition, 92(5), 799-808.
  4. Elia, M. (2003). The 'MUST' report. Nutritional screening for adults: a multidisciplinary responsibility. BAPEN.