Sugar crash

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Reactive hypoglycemia
Classification and external resources
ICD-9-CM 251.2
MeSH D007003

A sugar crash or glucose crash is the fatigue after consuming a large quantity of carbohydrates, also known as reactive hypoglycemia. It is variously described as a sense of tiredness, lethargy, irritation, or hangover, although the effects can be less if one has undertaken a lot of physical activity within the next few hours after consumption. The alleged mechanism for the feeling of a crash is correlated with an abnormally rapid rise in blood glucose after eating. This normally leads to insulin secretion (known as an insulin spike), which in turn initiates rapid glucose uptake by tissues either accumulating it as glycogen or utilizing it for energy production. The consequent fall in blood glucose is indicated as the reason for the "sugar crash".[1]

Sugar crashes are not to be confused with the after-effects of consuming large amounts of protein, which produces fatigue akin to a sugar crash, but are instead the result of the body prioritising the digestion of ingested food.[2]


Symptoms associated with sugar crashes are similar to those experienced during periods of hypoglycemia, though not as severe. This is because the difference between usual and post-meal blood glucose levels is not as large as in diabetic cases of hypoglycemia. A crash is usually felt within four hours or less of heavy carbohydrate consumption. Symptoms of reactive[3] or postprandial hypoglycemia include:

  • Confusion and difficulty concentrating on daily tasks
  • Anxiety
  • Light-headedness
  • Fatigue
  • Headache
  • Irritability[4][5]

The majority of these symptoms, often correlated with feelings of hunger, mimic the effect of inadequate sugar intake as the biology of a crash is similar in itself to the body’s response to low blood sugar levels following periods of glucose deficiency.[6]


The body requires a relatively constant input of glucose, a sugar produced upon digestion of carbohydrates, for normal functioning. Glucagon and insulin are among the hormones that ensure a normal range of glucose in the human body.[7] Upon consumption of a meal, blood sugar normally rises, which triggers pancreatic cells to produce insulin. This hormone initiates the absorption of the just-digested blood glucose as glycogen into the liver for metabolism or storage, thereby lowering glucose levels in the blood. In contrast, the hormone glucagon is released by the pancreas as a response to lower than normal blood sugar levels. Glucagon initiates uptake of the stored glycogen in the liver into the bloodstream so as to increase glucose levels in the blood.[8] Sporadic, high-carbohydrate snacks and meals are deemed the specific causes of sugar crashes. The “crash” one feels is due to the rapid increase and subsequent decline of blood sugar in the body system as one begins and ceases consumption of high-sugar foods. More insulin than is actually needed is produced in response to the large, rapid ingestion of sugary foods.


As it is a short-term ailment, a sugar crash does not usually require medical intervention in most people. The most important factors to consider when addressing this issue are the composition and timing of foods.[9] Acute low blood sugar symptoms are best treated by consuming small amounts of sweet foods, so as to regain balance in the body’s carbohydrate metabolism. Suggestions include sugary foods that are quickly digested, such as:

  • Dried fruit
  • Soft drinks
  • Juice
  • Sugar as sweets, tablets or cubes[10]

Tips to prevent sugar crashes include:

  • Avoiding eating meals or snacks composed entirely of carbohydrates; simultaneously ingest fats and proteins, which have slower rates of absorption.
  • Consistently choosing longer lasting, complex carbohydrates to prevent rapid blood-sugar dips in the event that one does consume a disproportionately large amount of carbohydrates with a meal
  • Monitoring any effects medication may have on symptoms[1]
  • Limiting sugar intake on an empty stomach unless the sugar is ingested in order to facilitate the uptake of proteins or supplements
  • Regularly practicing physical exercise.

One possible method to help prevent lethargy associated with high-carbohydrate meals is to impede the rate of absorption of sugars into the body by slowing the digestion process. This may be accomplished by drinking a cold liquid such as water or cold tea with, or shortly after, high-carbohydrate meals. This may have the effect of reducing the severity of the insulin spike, and reducing the intensity of lethargy. Drinking warm or hot liquids with high-carbohydrate meals can increase the metabolic rate of digestion, increasing the insulin spike and severity of lethargy. This can also apply to warm, weakly caffeinated drinks such as weak coffee or tea, especially if taken with milk.[citation needed]

See also[edit]


  1. ^ a b Hendrickson, Kirstin. "Side Effects of a Sugar Overdose". Demand Media, Inc. Retrieved 8 November 2011. 
  2. ^ "The Truth about Tryptophan". WebMD. 
  3. ^ "Hypoglycemia". National Diabetes Information Clearinghouse. U.S. Department of Health and Human Services. Retrieved 8 November 2011. 
  4. ^ "Hypoglycemia". Mayo Foundation for Medical Education and Research. Mayo Clinic. Retrieved 8 November 2011. 
  5. ^ Simpson, Jamie. "Causes of Low Blood Sugar". Demand Media. Retrieved 8 November 2011. 
  6. ^ "Diabetes". American Dietetic Association. Retrieved 11 November 2011. 
  7. ^ "How the Body Controls Blood Sugar". Web MD Diabetes. Healthwise Incorporated. Retrieved 8 November 2011. 
  8. ^ "Hypoglycemia". Hormonal and Metabolic Disorders. Merck Sharp & Dohme Corp. Retrieved 8 November 2011. 
  9. ^ Collazo-Clavell, Maria. "Reactive Hypoglycemia". Mayo Foundation for Medical Education and Research. Retrieved 11 November 2011. 
  10. ^ "Hypoglycemia (Low Blood Sugar) in People Without Diabetes". Diabetes Health Center. WebMD, LLC. Retrieved 8 November 2011.