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Does Phentermine Cause Constipation?

Weight loss journeys often involve a combination of dietary adjustments, exercise, and sometimes, medication. Phentermine has emerged as a popular choice for individuals aiming to shed excess pounds efficiently. However, concerns have arisen about a potential side effect of this medication – constipation. In this article, we will explore the intricate connection between phentermine and constipation, examining its prevalence, underlying mechanisms, and actionable strategies for prevention and relief.

Phentermine and Constipation: Separating Myth from Reality

The claim that nearly 50% of phentermine users experience constipation has been widely circulated, yet evidence suggests a more nuanced perspective. A study published in the Yonsei Medical Journal found that only 13% of users reported constipation, compared to an 8% rate in the placebo group. Another extensive study involving over 700 participants reported a constipation rate of 2.3%, with dry mouth being the predominant side effect.

These findings highlight that while constipation can indeed arise as a side effect of phentermine, its occurrence is considerably lower than often portrayed. Thus, while vigilance is warranted, the likelihood of experiencing this side effect is relatively modest.

How Phentermine Triggers Constipation

The connection between phentermine and constipation is linked to dietary changes associated with its use:

  1. Reduced Fiber Intake: As individuals begin taking phentermine, their dietary habits may shift, resulting in a decreased consumption of fiber-rich foods. Adequate dietary fiber aids in water absorption within stools, facilitating smoother passage. Insufficient fiber intake can lead to the formation of hard stools, a primary cause of constipation.
  2. Dehydration: Phentermine, functioning as a central nervous system stimulant, might inadvertently cause users to ignore fundamental physiological cues such as thirst. In a manner similar to its appetite-suppressing effect, phentermine can lead to dehydration. Insufficient water intake can result in rigid stools that are difficult to pass, with dehydration emerging as a key contributor to chronic constipation.

Navigating Constipation: Strategies for Prevention and Relief

Does Phentermine Cause Constipation?

To mitigate constipation while reaping the benefits of phentermine, adopting a proactive approach is crucial:

  1. Increase Fiber Consumption: Integrate a variety of high-fiber foods into your diet, including fruits, vegetables, whole grains, legumes, and nuts. Aim for a daily fiber intake of 25-30 grams, gradually increasing it to avoid digestive discomfort.
  2. Prioritize Hydration: Consume an adequate amount of water throughout the day, equivalent to at least 8 cups (64 ounces). Optimal hydration imparts flexibility to stools and prevents dehydration, a significant contributor to constipation. Carrying a reusable water bottle or using time-marked bottles can encourage consistent water consumption.
  3. Regular Physical Activity: Engage in regular physical exercise, as it stimulates bowel movements and promotes a healthy digestive system. Strive for a minimum of 30 minutes of moderate-intensity exercise on most days of the week.
  4. Maintain Consistent Meal Times: Adhering to a regular meal schedule regulates digestion and encourages bowel movements. Predictable meal times optimize the digestive process.
  5. Limit Processed Foods: Minimize the consumption of processed foods, known for their low fiber content and unhealthy fats. Additionally, certain additives and preservatives present in processed foods can disrupt digestion and exacerbate constipation in susceptible individuals.
  6. Consider Fiber Supplements: If meeting fiber requirements through diet is challenging, consult a healthcare professional about incorporating fiber supplements like psyllium husk and methylcellulose.

Understanding the Bigger Picture

Recognizing the multifaceted nature of constipation’s origins sheds light on the fact that it is not an isolated consequence of phentermine usage. Rather, its emergence is significantly influenced by the dietary selections made and the adequacy of fluid intake while under the influence of phentermine. The persistent efficacy of phentermine as an agent for weight loss enhancement remains apparent. Nevertheless, a comprehensive strategy that addresses the possible occurrence of constipation is imperative, aligning with the broader goal of holistic health enhancement.

Balancing Weight Loss and Digestive Wellness

As individuals embark on their weight loss endeavors, it is essential to acknowledge that phentermine’s impact goes beyond the scales. This medication’s potential side effect of constipation underscores the interconnectedness of bodily functions. While phentermine serves as a potent tool in the pursuit of weight reduction, it simultaneously necessitates a proactive stance towards maintaining optimal digestive health.

Synergy of Well-Being

The harmony between phentermine and the weight loss journey becomes more profound when one considers the intricate relationship between dietary habits, fluid consumption, and the potential for constipation. This synergy invites individuals to view their health through a holistic lens, where both the intended outcomes of weight loss and the potential challenges of constipation are acknowledged and addressed.


The synergy of phentermine and the weight loss journey holds immense potential. For those grappling with constipation, reassurance can be found in actionable solutions. While phentermine serves as a potent ally in expedited weight loss, seeking professional guidance before embarking on its usage, especially for individuals with underlying medical conditions, is paramount. Through a holistic approach, individuals can harness the advantages of phentermine while effectively managing and preventing constipation, ensuring a journey towards improved overall well-being.


Meet Dinky, a Ramapo College of New Jersey alumnus who traded in her pen and notebook for a barbell and stopwatch. Dinky has been flexing her writing muscles for over four years as a journalist. She’s now bringing her expertise to, where she covers the latest and greatest in fitness trends, health, and lifestyle topics. But Dinky doesn’t just write about fitness – she lives it. She’s a regular at the gym and has a passion for CrossFit and bodybuilding competitions, making her the ultimate insider in the fitness industry. So whether you’re looking for workout inspiration, the latest supplement reviews, or coverage of the biggest competitions, Dinky’s got you covered.

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