What could cause sudden weakness after a bowel movement?
Ask the doctor
Q. After a bowel movement I get very weak and have to lie down, and sometimes fall asleep. It takes me several hours to get back to normal. Why would this happen?
A. Most likely this is a vasovagal reaction. Here's what I mean: Often people need to tense their abdominal muscles and strain a bit during a bowel movement. This tends to stimulate the vagus nerve. A stimulated vagus nerve slows the heart rate.
At the same time, when you tense your abdominal muscles, blood flow back to the heart decreases a bit. This results in a lower blood pressure.
The combination of a slower heart rate and lower blood pressure could make you feel lightheaded and weak.
I would expect the symptoms to resolve over a few minutes once you lie down. But the fact that it takes you several hours to feel normal makes me concerned that there may be something else contributing to these "weak spells."
I suggest you make an appointment with your doctor. There's still a good chance that your doctor won't find anything else. The reason for weak spells often cannot be diagnosed. But your doctor will want to consider underlying problems, such as anemia (low red blood cell count) or heart disease.
Image: © dowell/Getty Images
About the Author
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
Disclaimer:
As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles.
No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.
