Should you be concerned about undigested Metformin in stool? 

Should you be concerned about undigested Metformin in stool? 

You should not be concerned if you see undigested Metformin tablets in your stool. Seeing white tablets in your stool is a common case with Metformin extended-release tablets and it shouldn’t scare you. 

The tablet you see in your stool is just the coating, the shell of the tablet. It doesn’t mean that your Metformin is just being eliminated without doing what it’s supposed to. 

This is because the active ingredient from these coatings gets released into your stomach and the unwanted shell is eliminated from your body via stool. 

These eliminated tablet coatings are often called ‘ghost tablets‘. So, don’t worry if you keep seeing these empty tablets in your stool. In some cases, they may look like parasites in the stool, but it’s just the empty coating of the medication (1,2). 

This doesn’t indicate therapeutic failure and you should keep taking your medication properly. You can rest assured that the medication will manage your symptoms effectively. 

How to ensure the safe and effective use of Metformin?

To ensure the safe and effective use of Metformin, it’s important to follow these guidelines (3):

  • Take Metformin exactly as prescribed by your healthcare provider. 
  • Take Metformin with meals to minimize stomach discomfort and improve absorption. Try to take it at the same time every day to establish a routine.
  • Take Metformin consistently and do not skip doses. If you miss a dose, take it as soon as you remember unless it is close to the time for your next dose.  
  • Maintain a healthy diet and exercise regularly as advised by your healthcare provider. Metformin works best when combined with a balanced diet and an active lifestyle.
  • Your healthcare provider may periodically monitor your blood sugar levels to assess the effectiveness of Metformin.
  • Keep your healthcare provider informed about your medical history, including any other medications, supplements, or health conditions you have.  
  • Limit your alcohol intake while taking Metformin, as alcohol can increase the risk of lactic acidosis and other side effects. 
  • Store Metformin at room temperature, away from moisture and heat. Check the expiration date and dispose of any expired medication properly. 

Final words

To sum up, Metformin ghost tablets are nothing to worry about and it is generally not a cause of concern. However, it’s still advisable t discuss this with your healthcare provider. It is also important to ensure the safe and effective use of Metformin to make the most out of it.

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Porte L, Weitzel T. Ghost tablets mimicking intestinal parasite. Braz J Infect Dis. 2019 Nov-Dec;23(6):462-463. doi: 10.1016/j.bjid.2019.10.006. Epub 2019 Nov 14. PMID: 31734173; PMCID: PMC9428199.


Tungaraza TE, Talapan-Manikoth P, Jenkins R. Curse of the ghost pills: the role of oral controlled-release formulations in the passage of empty intact shells in faeces. Two case reports and a literature review relevant to psychiatry. Ther Adv Drug Saf. 2013 Apr;4(2):63-71. doi: 10.1177/2042098612474681. PMID: 25083252; PMCID: PMC4110830.


Corcoran C, Jacobs TF. Metformin. 2022 May 2. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–. PMID: 30085525.