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Learn more about the results we get at Within

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Why does bulimia shaking occur?

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Shaking, or trembling, can sometimes occur after purging in individuals with bulimia nervosa (BN). This has sometimes been explained like this: “I feel really weak and like I’m vibrating from the inside out. My hands are shaking.”

Some people who experience bulimia shaking after purging tend to decide to address it with water consumption or sleeping. Others simply lie down for a while until it passes.

 sources cited
Last updated on 
October 27, 2022
In this article

What happens in the body from vomiting?

Vomiting can be induced, as is the case of those with bulimia, but you should know that the whole process is actually controlled by reflexes. There’s a “vomiting center” inside the brain in the fourth ventricle called the chemoreceptor trigger zone (CTZ) or also called the area postrema. This area is outside the blood-brain-barrier so drugs and medications can stimulate the area. Once this chemoreceptor trigger zone is stimulated, vomiting occurs. (1)

Vomiting may occur several different ways:

  1. When the gag reflex is initiated by irritation or stimulation of the back of the throat via the vagus nerve or cranial nerve X, which carry signals to the CTZ.
  2. When stress or psychiatric conditions activate dopamine receptors
  3. When the gut nervous system sends signals on the vagus nerve to the brain. This is how therapies such as chemotherapy and radiation therapy activate the 5-HT3 receptors leading to vomiting.
  4. When the inner ear vestibular system receives messages about motion sickness from cranial nerve VIII

Both parts of the central nervous system – the parasympathetic and sympathetic are involved in vomiting. At first before vomiting, the parasympathetic nervous system is activated along with the sympathetic system. The first symptoms are increased salivation and deep breathing followed by heaving or retching. Then the sphincter between the stomach and the rest of the upper GI tract leading to the mouth is relaxed. All these are parasympathetic symptoms. 

The abdominal pressure rises and the pressure within the chest is lowered to make vomiting possible. When the abdominal muscles contract, the vomit comes up. Finally the sympathetic nervous system signs appear and there is sweating, palpitation, and rapid heart rate. This is when bulimia shaking may occur.

As you can see, all this is controlled by your body’s own nervous system. You have very little if any control over the process if not self-induced. 

There’s another aspect of self-induced vomiting that may need to be considered in this process. It’s your blood sugar levels. Low blood sugar symptoms include feeling shaky, sweating, clamminess, fast heartbeat, feeling lightheaded, headaches and seizures (if it’s too low). 

After you eat a meal or any food, your blood sugar starts to rise. This happens because the sugar that was in food gets released through the process of digestion. Then as the sugar gets released in the GI tract, it makes its way to the bloodstream, raising your glucose levels. This is when the bloodstream delivers glucose to the rest of your body. Blood sugar regulation is controlled by insulin. When the cells take in the blood sugar, the levels in the blood drop. 

When someone eats, blood sugar levels will rise. If they rise to above 180 mg/dL, this can cause symptoms of hyperglycemia (high blood sugar). The early signs and symptoms of hyperglycemia include blurred vision, increased thirst, frequent urination, fatigue and headache. (2) Later signs and symptoms include nausea and vomiting, dry mouth, confusion, fruity-smelling breath, abdominal pain, weakness, and coma.

On the other hand, hypoglycemia (low blood sugar) can occur and is common in individuals with eating disorders and can also cause bulimia shaking. (4) Hypoglycemia can be treated by consuming quickly absorbable sugar like apple juice or hard candy. You can prevent low blood with proper nourishment but someone and treatment of low blood sugar should be addressed with a medical provider.

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When to seek medical intervention

If you or a loved one have bulimia and tremble, understand that this is most likely a temporary situation due to the nervous system changes that occur with vomiting. 

However, one of the big problems associated with vomiting is potential electrolyte disturbances, which can cause any of the following symptoms:

  • Light-headedness
  • Dizziness
  • Chest pains
  • Shortness of breath
  • Weakness 
  • Numbness
  • Change in mental alertness

When should you seek medical attention after vomiting? Vomiting can lead to dehydration, which could become a serious medical emergency. You can die from dehydration as well as from electrolyte disturbances. 

Below are four instances when you always want to head to the emergency room following vomiting: (3)

  1. If there is vomiting of blood, it’s imperative to go to the emergency room, as there may be some bleeding occurring in any of the tissues or arteries of the upper gastrointestinal system. 
  2. If you have a fever or also have bloody diarrhea, it may indicate there’s food poisoning involved. It’s possible that during the binge, some of the foods were affected with a food-borne illness.
  3. If you have pain in your abdomen, lethargy and confusion, it’s also imperative to go to the emergency room for a medical workup. 
  4. If you can’t keep down clear fluids after throwing up, this is another sign to seek medical attention as soon as possible.

Disclaimer about "overeating": Within Health hesitatingly uses the word "overeating" because it is the term currently associated with this condition in society, however, we believe it inherently overlooks the various psychological aspects of this condition which are often interconnected with internalized diet culture, and a restrictive mindset about food. For the remainder of this piece, we will therefore be putting "overeating" in quotations to recognize that the diagnosis itself pathologizes behavior that is potentially hardwired and adaptive to a restrictive mindset.


  1. Mandal, D. A. (2019, February 27). Vomiting mechanism. News. Retrieved October 7, 2022, from https://www.news-medical.net/health/Vomiting-Mechanism.aspx 
  2. Mayo Foundation for Medical Education and Research. (2022, August 20). Hyperglycemia in diabetes. Mayo Clinic. Retrieved October 7, 2022, from https://www.mayoclinic.org/diseases-conditions/hyperglycemia/symptoms-causes/syc-20373631 
  3. Team, D. H. (2021, March 8). Do you know when to visit the hospital for vomiting? Cleveland Clinic. Retrieved October 7, 2022, from https://health.clevelandclinic.org/what-causes-vomiting-and-what-should-you-do-about-it/ 
  4. Mehler, P. S., & Brown, C. (2015). Anorexia nervosa - medical complications. Journal of eating disorders, 3, 11. https://doi.org/10.1186/s40337-015-0040-8


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