How to Read Adult MUAC for Nutritional Assessment

October 22, 2025 •

4 min read

According to a 2017 meta-analysis, the Mid-Upper Arm Circumference (MUAC) measurement is highly effective in distinguishing between adults with healthy Body Mass Index (BMI) and those who are underweight. Learning how to read adult MUAC is a crucial skill for health workers, caregivers, and individuals monitoring their nutritional status, especially in resource-limited settings. This method offers a simple, non-invasive alternative to BMI, requiring minimal equipment and training.

Quick Summary

This guide provides a comprehensive overview of how to properly measure and interpret adult mid-upper arm circumference. It details the step-by-step procedure, explains the significance of the color-coded tape and specific cut-off points, and clarifies why this method is a vital tool for assessing nutritional status and identifying health risks.

Key Points

Measurement Technique: Use a non-stretchable MUAC tape on the midpoint of a relaxed, non-flexed left upper arm.
Standard Cut-offs: For adults, readings below 21 cm often indicate severe malnutrition (red), 21-23 cm indicate moderate risk (yellow), and above 23 cm suggest a healthy status (green).
Tool for Undernutrition: MUAC is particularly effective for screening for underweight in adults, correlating well with low BMI.
Alternative to BMI: It is a simple and reliable alternative to Body Mass Index, especially for immobile patients or during large-scale community screenings.
Interpreting Colors: The color-coded system allows for rapid assessment of nutritional status, making it accessible to health workers with minimal training.
Ethnicity Variations: Note that while standard cut-offs exist, population-specific variations may apply, and some adult tapes are not color-coded.

Why Use MUAC for Adult Nutritional Assessment?

Mid-Upper Arm Circumference, or MUAC, has gained significant traction as a simple, effective tool for nutritional screening in adults, especially where traditional methods like calculating Body Mass Index (BMI) are impractical. Factors such as immobility, oedema, or lack of proper equipment can make BMI measurements difficult. MUAC, by contrast, requires only a flexible, non-stretchable tape and minimal training, making it ideal for large-scale screenings, remote field operations, and community-based health programs. It is an effective proxy for BMI and has been shown to be a good predictor of health outcomes related to undernutrition.

A Step-by-Step Guide to Measuring Adult MUAC

To ensure an accurate and reliable reading, the correct procedure must be followed precisely. A standardized, non-stretchable MUAC tape, often color-coded, is required.

Procedure for MUAC Measurement

Patient Positioning: Ask the person to stand or sit with their left arm hanging freely and relaxed at their side. The left arm is typically used for consistency, but if it is not possible, the right arm can be used. The patient should not flex the arm during the measurement.
Locate the Midpoint: Find the bony prominence of the shoulder (the acromion) and the tip of the elbow (the olecranon process). Bend the arm to a 90-degree angle to make this easier. Measure the distance between these two points with the tape. Mark the midpoint with a pen or by folding the tape in half.
Position the Tape: Ask the person to relax their arm again, letting it hang straight down. Wrap the MUAC tape snugly but not too tightly around the arm at the midpoint you just marked. The tape should lie flat against the skin.
Read the Measurement: Read the number that appears in the designated window on the tape, typically measured to the nearest millimeter or 0.1 cm. Note this measurement down accurately.
Check for Tension: Ensure the tape is taut but not compressing the arm. A common error is pulling the tape too tight or leaving it too loose, which can skew the result.

Interpreting Adult MUAC Readings

Interpretation of adult MUAC readings is crucial for determining nutritional status. While the standard color-coded tapes are most commonly associated with child malnutrition, specific adult cut-off points have been established. It is important to note that specific cut-offs may vary based on ethnicity, so population-specific data should be used where available.

Standard MUAC Color Codes and Interpretations for Adults

Green: Indicates a healthy nutritional status. The specific value depends on the tape used, but is generally above a certain threshold (e.g., above 23 cm).
Yellow: Represents a risk of moderate malnutrition. This usually falls within a specific range, such as 21 cm to 23 cm.
Red: Signifies severe acute malnutrition (SAM). Measurements in this range, typically below 21 cm, indicate a high health risk and require immediate intervention.

Comparison Table: MUAC vs. BMI for Nutritional Screening


Feature	MUAC Measurement	BMI Calculation
Equipment	Non-stretchable, color-coded tape measure.	Calibrated weighing scale and stadiometer.
Logistics	Simple, portable, and quick. Ideal for field and community settings.	Requires more equipment and space, can be complex in certain situations.
Applicability	Highly reliable in situations where BMI is impractical (e.g., oedema, immobility).	Standard gold-standard indicator, but less useful for bedridden or immobile patients.
Skill Level	Requires minimal training, making it accessible to a wider range of healthcare workers.	Requires some technical skill and calculation to interpret.
Assessment Speed	Rapid, providing an immediate color-coded result.	Requires a two-step process of measurement and calculation.

Conclusion

Learning how to read adult MUAC is a critical skill for quick and effective nutritional screening. As a simple and practical anthropometric measure, MUAC provides a reliable alternative to BMI in many contexts, especially in resource-constrained environments or for immobile patients. By following the correct procedure and understanding the color-coded cut-off points, health professionals and caregivers can accurately assess an individual's nutritional status and identify those at risk of malnutrition. While MUAC is an excellent screening tool, it should be used as part of a broader nutritional assessment strategy and not as a single diagnostic measure. Continued training and validation studies are important for ensuring its accuracy across diverse populations. For further authoritative information on nutritional assessment, refer to resources from organizations like the World Health Organization (WHO) or professional nutritional societies. For instance, the Journal of Parenteral and Enteral Nutrition offers extensive evidence-based resources for clinical nutrition and metabolic support.

Disclaimer: The information provided is for educational purposes and should not replace professional medical advice. Always consult a healthcare provider for any health concerns or before making changes to your health or nutrition plan.

Frequently Asked Questions

To take an adult MUAC, locate the midpoint of the non-dominant upper arm between the shoulder and elbow. Wrap a non-stretchable tape measure around this midpoint with the arm relaxed and hanging at the person's side, and read the measurement in the tape's window.

On a color-coded adult MUAC tape, a measurement in the green section typically indicates a healthy nutritional status, yellow indicates a risk of acute malnutrition, and red indicates severe acute malnutrition (SAM).

MUAC is often used as a more practical alternative to BMI when height and weight measurements are difficult, such as with bedridden patients, individuals with fluid retention (oedema), or in remote settings with limited equipment.

Yes, some studies suggest gender-specific MUAC cut-offs. For instance, a MUAC below 25 cm for men and 24 cm for women might indicate acute malnutrition. Always use the appropriate guidelines for the population being screened.

Yes, MUAC is a useful tool for screening pregnant and postpartum women for malnutrition risk, with specific cut-off points often used to guide care.

While MUAC is very effective for screening underweight and malnutrition, its correlation with obesity is slightly weaker than for underweight. Some studies have proposed MUAC cut-offs for overweight and obesity, but its primary strength lies in identifying undernutrition.

MUAC tapes for both adults and children are available through various medical suppliers and aid organizations. UNICEF, for example, stocks different types and provides specifications for their tapes.