Does Adipex cause constipation? (+3 tips)

In this article, we will explore whether Adipex can cause constipation or not, how Adipex can cause constipation, what factors contribute to Adipex-induced constipation, what to do if Adipex causes constipation and how to manage Adipex-induced constipation. 

Does Adipex cause constipation?

Yes, Adipex (phentermine) can cause constipation. Constipation is a fairly common gastrointestinal side effect of Adipex reported by the patients taking Adipex. About 10% of the patients taking Adipex have reported suffering from constipation after taking Adipex for weight loss.

Adipex is a brand name of phentermine that belongs to the class of anorectics or appetite suppressants. It is a prescription weight loss medication that works for short-term weight loss by suppressing appetite and increasing energy expenditure leading towards weight loss. Due to its stimulant-like effects on the body, it is prescribed for short-term use only (1).

If you are taking Adipex for weight management and experience constipation, then consulting your healthcare provider is the best option to get a safe and effective treatment strategy.

How does Adipex cause constipation?

Adipex has stimulatory actions on the central nervous system. It increases the norepinephrine levels in the brain (2). These neurotransmitters are involved in digestion. The increase in the levels of norepinephrine causes the food to move slowly in the gastrointestinal tract causing more absorption of water and harder, drier stools leading towards constipation (3). 

Adipex, because of its appetite-suppressing properties, also leads to decreased thirst causing decreased intake of water. This exacerbates the condition causing constipation.

The movement of the food in the gastrointestinal tract may also be slowed by the direct action of phentermine on gut motility (4). It weakens the contractions of the muscle of the gut leading to slower movement of food causing increased water absorption resulting in constipation.   

What factors contribute to Adipex-induced constipation?

Here are some factors that may contribute to Adipex-induced constipation. 

Dosage and duration

Higher doses are associated with an increased risk of side effects. Increased and prolonged dosing of Adipex can contribute to not only the therapeutic effect but the adverse effects as well. Higher doses can increase the levels of norepinephrine leading towards an increased risk of constipation.

Individual sensitivity

The effects of Adipex may vary from patient to patient. Not every person taking Adipex will experience the same effects of the medications. Some might experience intense and severe constipation whereas others may not even observe a mild constipation. 

The variations among individuals may be due to physiological factors, pharmacological factors, age or gender etc. 

Underlying health condition

Underlying health conditions such as Inflammatory bowel syndrome, Crohn’s disease, metabolic disorder, and pelvic floor dysfunction can lead to drug-disease interaction causing constipation as a side effect. If you have any of these medical conditions, it is better to inform your doctor about it.  

Concurrent medication

Patients taking medications such as opioid pain medication, anticholinergic medications or any other weight loss supplement or medication, then you are more likely to experience constipation after taking Adipex as compared to the patients who are not taking any of these along with Adipex. 


Dehydration and inadequate diet issues can also contribute to constipation in patients taking Adipex. Consumer meals or low-fibre food can badly affect bowel movements and lead the patient towards constipation exacerbating the condition. 

What to do if Adipex causes constipation?

If you are taking Adipex for weight loss or weight management and experience constipation then you need to consult your healthcare provider in order to address your concerns. 

Consulting healthcare professional

Your doctor will help you to determine the exact cause of constipation through careful examination and considering your past medical history. If Adipex is found to be your cause then your doctor will help you modify your treatment plan. 

Lowering the dose of Adipex can be helpful. Lower doses can help your body adjust better to the effects of Adipex. Modifications in the dosage regimen can be helpful in lowering the severity of constipation caused by Adipex.

To help you treat your condition of constipation your doctor may prescribe one of the following medications to help with constipation while taking Adipex (5).

  • Docusate sodium
  • Osmotic laxatives
  • Bulk-forming laxatives
  • Lubricants

However, if the symptoms do not subside even after modifying the treatment plan then your doctor will have to switch your medication and prescribe you an alternative treatment. The alternative medications may include:

  • Orlistat
  • Lorcaserin
  • Phentermine-Topiramate (Qsymia)
  • Contrave

How to manage Adipex-induced constipation?

Here are a few tips to manage Adipex-induced constipation.

  • Taking a fibre-rich diet is essential. You need to take in about 25-35g of fibre. The major sources of fibre are fruits, vegetables and whole grains. 
  • Dehydration can worsen the impact. 8-10 glasses of water are necessary per day.
  • Processed food is not good for a patient suffering from constipation. 
  • Probiotics can be helpful with this condition as well.
  • Magnesium citrate can be helpful in treating constipation (6).
  • Regular exercise for 30 minutes can help regulate your bowel movement and contribute to the normal functioning of the body.

In my opinion, Adipex can cause constipation as it is a commonly reported side effect. However, not every individual taking Adipex will experience the same effects on their body. This is why an open communication with your healthcare provider is essential if you have any concerns regarding the effects of Adipex.

Over-the-counter medications can be help you to get relief from constipation. Your doctor can help you determine a safe and effective treatment plan to ensure a complete positive effect and minimal side effects.


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