Nutrition Diet: What is the position of the MUAC?

October 22, 2025 •

5 min read

According to UNICEF, MUAC screening is a simple yet vital tool for identifying malnutrition, particularly in children. Understanding precisely what is the position of the MUAC during this procedure is critical for ensuring the accuracy of nutritional assessments, which in turn informs necessary dietary interventions.

Quick Summary

Mid-upper arm circumference (MUAC) is a standard nutritional assessment. Accurate measurement requires placing the tape at the midpoint between the shoulder and elbow for reliable results in identifying malnutrition risk.

Key Points

Precise Placement: The correct MUAC position is the midpoint between the tip of the shoulder (acromion) and the elbow (olecranon process) on the non-dominant arm.
Accurate Measurement: Proper technique requires measuring on bare skin with the arm hanging loosely, ensuring the tape is snug but not too tight.
Indicator of Health: MUAC measures muscle and subcutaneous fat reserves, providing a reliable indicator of nutritional status, especially for screening malnutrition.
Critical Screening Tool: MUAC is particularly effective for assessing acute malnutrition and predicting mortality risk in children aged 6 to 59 months.
Guides Intervention: Color-coded MUAC tapes directly inform dietetic interventions, ranging from monitoring (green zone) to supplementary (yellow zone) and therapeutic feeding (red zone).
Simple and Cost-Effective: MUAC offers a practical, low-cost, and easy-to-use alternative to complex anthropometric measurements in resource-limited settings.

The Significance of MUAC in Nutritional Assessment

Mid-Upper Arm Circumference, or MUAC, is a measurement of the circumference of the upper arm, which provides a simple and effective indicator of nutritional status. It is a reliable proxy for the body's muscle and subcutaneous fat reserves, which are depleted during malnutrition. Due to its simplicity, low cost, and ease of use, MUAC is a cornerstone of public health screening programs, especially in contexts where more complex equipment like scales and stadiometers are not available. Its particular value lies in its ability to predict mortality risk in severely malnourished children aged 6 to 59 months, for whom it is a key diagnostic tool. But the reliability of this screening method hinges entirely on the correct technique, particularly the precise positioning of the measuring tape.

Step-by-Step: How to Determine the Correct Position of the MUAC

Achieving an accurate MUAC measurement involves a standardized procedure to ensure consistency and reliability. The correct position for the MUAC tape is at the midpoint of the non-dominant upper arm. For most individuals, this is the left arm. The following steps guide you through the process:

Prepare the arm: Ensure the individual's left arm is relaxed and hanging loosely at their side. The skin should be bare, so any clothing should be moved out of the way.
Locate anatomical landmarks: With the left arm bent at a 90-degree angle, palpate to find two key bony points: the acromion process (the bony point of the shoulder) and the olecranon process (the bony tip of the elbow).
Measure the midpoint: Place the zero end of a non-stretchable measuring tape at the acromion. Run the tape down the outside of the arm to the olecranon process. Note the measurement at the tip of the elbow and divide it by two to find the midpoint. Alternatively, some use a string or a special MUAC tape to bend the tape in half to find the midpoint.
Mark the midpoint: Use a pen or a fingertip to mark this midpoint on the skin. This is the precise position where the MUAC tape will be placed.
Relax and measure: Ask the individual to relax their arm again, so it hangs straight down. Wrap the MUAC tape snugly around the arm at the marked midpoint.
Ensure correct tension: The tape should be taut but not so tight that it compresses the underlying soft tissue or causes a skin indentation.
Read and record: Read the measurement in the window of the tape to the nearest millimeter. For color-coded tapes, record both the numerical value and the color.

The Critical Role of Accuracy

Errors in MUAC measurement can significantly affect nutritional diagnoses and treatment plans. Using the wrong arm, incorrectly estimating the midpoint, or applying the wrong tension can lead to misclassification of nutritional status. For instance, pulling the tape too tight could lead to an underestimation of nutritional reserves, while too loose a tape could have the opposite effect. Correct positioning ensures that the measurement reflects the true mass of the upper arm, consisting of muscle and fat, providing a consistent and comparable metric over time and across different individuals. This consistency is what makes MUAC a powerful screening tool in public health and emergency settings.

Comparison of MUAC and Other Anthropometric Measures

While MUAC is a highly practical and effective screening tool, especially in resource-limited settings, it is not the only metric for nutritional assessment. Here is a comparison of MUAC with other common anthropometric measures:


Feature	Mid-Upper Arm Circumference (MUAC)	Body Mass Index (BMI)	Weight-for-Height Z-Score (WFH-Z)
Equipment	Simple, inexpensive tape	Scale and stadiometer	Scale and stadiometer
Feasibility	Excellent in field settings; quick and easy.	Requires more equipment and space.	Requires more equipment and more complex calculation.
Accuracy	Reliable for screening acute malnutrition.	Good for general population screening.	The standard for childhood malnutrition but requires accurate height/length measurement.
Impact of Edema	Less affected by swelling (edema) in the arms.	Can be artificially inflated by fluid retention.	Also affected by fluid retention, making interpretation difficult.
Age Dependency	Largely age-independent for children 6-59 months, simplifying screening.	Age and sex-specific cutoffs are required.	Age and sex-specific cutoffs are required.
Risk Prediction	Superior predictor of mortality risk in children.	A good indicator of obesity and health risk in adults.	Key for diagnosing wasting but less predictive of mortality than MUAC.

How MUAC Guides Nutrition Diet Plans

For dietitians and nutritionists, the MUAC measurement is an important piece of the puzzle for determining a patient's nutritional needs. The results from a MUAC screening directly inform the type and urgency of nutritional intervention:

Severely Malnourished (Red Zone): A very low MUAC reading (e.g., < 115mm in children 6-59 months) indicates Severe Acute Malnutrition (SAM). This necessitates immediate, intensive therapeutic feeding using nutrient-dense, ready-to-use therapeutic food (RUTF) to save the individual's life.
Moderately Malnourished (Yellow Zone): A moderate MUAC reading (e.g., 115mm to < 125mm in children) suggests Moderate Acute Malnutrition (MAM). This calls for supplementary feeding and regular monitoring to prevent the condition from worsening.
Normal (Green Zone): A healthy MUAC reading (e.g., $\geq$ 125mm in children) indicates a normal nutritional status. While no immediate nutritional crisis exists, the individual's overall dietary habits and health should still be considered for a balanced diet.

Following a nutrition diet based on MUAC results can be a life-saving intervention. It is particularly effective in community-based programs where resources are limited, and rapid, on-site assessment is essential.

The Role of Trained Personnel and Standardized Procedures

While MUAC measurement is simple enough for caregivers to learn, proper training is essential to minimize technical errors and ensure accuracy. Organizations like UNICEF have developed extensive training materials to guide health workers and volunteers in the correct procedure. Consistent methodology and calibration of the tapes help to maintain the integrity of the data collected, which is used not only for individual patient care but also for broader public health monitoring. The use of standardized color-coded tapes and clear reporting protocols ensures that MUAC results can be interpreted consistently, enabling effective decision-making across different health facilities and regions.

Conclusion

Understanding what is the position of the MUAC is the foundation of an accurate mid-upper arm circumference measurement. By correctly identifying the midpoint between the acromion and olecranon on the non-dominant arm, healthcare workers and caregivers can utilize this simple yet powerful tool to reliably screen for malnutrition. The MUAC measurement is a vital component of nutritional dietetics, enabling rapid identification of at-risk individuals and guiding appropriate, timely interventions. Whether in remote community settings or clinical environments, the correct technique ensures that MUAC remains a trusted and effective indicator of nutritional health.

For additional resources on MUAC guidelines and best practices, consult authoritative sources such as the UNICEF MUAC Guidelines.

Frequently Asked Questions

The left arm is typically chosen for MUAC measurements as a standard practice to ensure consistency across different screenings. The non-dominant arm is generally preferred because it tends to have more stable muscle and fat mass, leading to more comparable results.

A special, non-stretchable MUAC tape is the primary tool needed. Some tapes are color-coded (red, yellow, green) for easier interpretation, while others just have millimeter markings. You may also need a pen to mark the midpoint.

To find the midpoint, first bend the individual's elbow to a 90-degree angle. Measure the distance between the tip of the shoulder (acromion process) and the tip of the elbow (olecranon process). The midpoint is exactly halfway along this distance.

The tape should be snug but not so tight that it indents the skin or compresses the muscle. The goal is a firm, consistent pressure that accurately measures the circumference without distorting the underlying tissue.

While MUAC correlates with BMI and can indicate overweight or obesity, it is primarily validated and recommended as a screening tool for undernutrition and wasting. For accurate obesity screening, BMI is generally the preferred indicator, especially for adults.

MUAC is particularly valuable for children aged 6-59 months, as it is relatively age-independent during this period and highly predictive of mortality risk. It is also used in adults and pregnant women, but standard cutoffs vary by population, and its interpretation needs to be age-appropriate.

In developing countries, MUAC is a critical public health tool because it is inexpensive, portable, and requires minimal training. It allows community health workers to quickly and efficiently screen large populations for malnutrition, enabling timely referral and intervention.