Five Common Mistakes in Oral Nutritional Supplement Use—and How to Fix Them

Author: Ezgi Pınar

Istanbul University, Istanbul Faculty of Medicine, Department of Internal Medicine, Division of Geriatrics

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Malnutrition is a prevalent condition among older adults and strongly associated with increased mortality, morbidity, and functional decline (1). Oral Nutritional Supplements (ONS) are an evidence-based, practical tool to support nutritional intake in those who are unable to meet nutritional targets through regular food alone. However, in everyday clinical practice, several common mistakes reduce the effectiveness of ONS therapy. As early-career geriatricians, highlighting these points is crucial to ensure that this beneficial intervention is implemented correctly and effectively. This brief piece highlights the five most frequent pitfalls and offers practical strategies to address them (2, 3).

1. Delaying the initiation of ONS 

A frequent misconception is that ONS should only be started once significant weight loss has already occurred. However, early initiation—particularly in patients at risk of malnutrition—yields better outcomes. Early support might also reduce complications and readmission risk.

2. Underdosing (relying on one bottle per day)

Many clinicians prescribe “one bottle daily” assuming it is sufficient. However, this dose is rarely adequate.  The European Society for Clinical Nutrition and Metabolism (ESPEN) guidelines recommend ≥400 kcal and ≥30 g protein per day (4), which typically requires at least two bottles. Suboptimal dosing leads to suboptimal results and might create the false impression that ONS “does not work.”

3. Using ONS as a meal replacement

ONS is designed to supplement, not replace, regular meals. When used instead of meals, total daily energy and protein intake might paradoxically decrease. The most effective timing is between meals, after meals, or before bedtime—times when it supports rather than competes with oral intake.

4. Failing to manage side effects (Nausea, Diarrhea, Bloating)

Mild gastrointestinal symptoms are the main causes of poor adherence. Rather than discontinuing ONS entirely, these issues could be solved by adjustments such as dividing the dose into smaller portions, drinking sip by sip, switching to a different formula, modifying fiber content. These strategies could significantly improve tolerance.

5. Not asking about the patients’ appetite and preferences

A common oversight is neglecting patients’ taste preferences, appetite fluctuations, or texture tolerances. These factors strongly affect adherence. Trying alternative flavors, different consistencies, or mixing ONS with familiar foods (e.g., coffee, cocoa, dairies, cinnamon, lemon or orange peels) could significantly improve tolerability. Individualized selection is the key to sustained use. 

In summary, effective ONS treatment depends on appropriate timing for initiation, adequate dosing, individualized problem-solving, and patient-centered selection. Avoiding these five common mistakes could greatly enhance adherence, improve clinical outcomes, and maximize the overall benefit of nutritional support in older adults.

Ref:    1. Cederholm T, Barazzoni R, Austin P, et al. ESPEN guidelines on definitions and terminology of clinical nutrition. Clin Nutr. 2017;36(1):49-64. doi:10.1016/j.clnu.2016.09.004

2. Bahat G, Pinar E, Abbasoglu O, et al. Nutritional care using oral nutritional supplements: 22 questions every clinician Asks-Answered by global experts in a Delphi consensus study. Clin Nutr. 2026;57:106552. doi:10.1016/j.clnu.2025.106552

3. Bahat G, Akmansu M, Gungor L, et al. Optimal use of oral nutritional supplements (ONS) in medical nutrition therapy: ONS consensus report from KEPAN. Eur J Clin Nutr. 2023;77(7):705-709. doi:10.1038/s41430-022-01229-9

4. Volkert D, Beck AM, Cederholm T, et al. ESPEN practical guideline: Clinical nutrition and hydration in geriatrics. Clin Nutr. 2022;41(4):958-989. doi:10.1016/j.clnu.2022.01.024