Warning Signs That Your Blood Sugar Is Falling Low
Defence against hypoglycemia
Hypoglycemia or lowering of blood sugar, is a biochemical entity, and is defined as a blood glucose concentration below 70 mg/dl.
Our brain is vulnerable to hypoglycemia, because it cannot utilize circulating free fatty acids as an alternative source of energy, in contrast to other vital organs of our body.
The short chain fatty acids called keto acids or ketone bodies can be utilized as energy substrate and protect the brain from damage, but development of ketones requires a number of hours. So ketosis is ineffective in protecting against sudden lowering of blood sugar.
Under ordinary circumstances energy requirements of the body are met by the food that we eat. Carbohydrates from the food are broken down into glucose that is utilized for energy production in the body.
When caloric intake is greater than the immediate requirements, as after the usual meal, excess nutrients are stored as fats, proteins and glycogen (the storage form of glucose).
This is the anabolic phase of metabolism in which the nutrients pass from intestine to liver to body organs for utilization and to storage sites.
The catabolic or breakdown phase of metabolism begins about 5 to 6 hours after a meal. Normally the only significant catabolic period in the day is during the overnight fast. During fasting or catabolism, the liver is activated to produce glucose from stored glycogen, in order to maintain the blood glucose level in a range safe for the brain function and free fatty acids are mobilized to provide energy source to most other body organs.
Since about 70 gms of glycogen is stored in the human liver, it can sustain plasma glucose levels only for 8 to 10 hours. Exercise and the stress of severe illnesses may further shorten this protective period.
After glycogen depletion in liver, lactate, pyruvate and amino acids from glycogen and proteins stored in muscles and glycerol from fat deposited in the body, are mobilized to the liver to be converted to glucose to maintain its blood levels.
Kidneys also contribute to half of the required glucose production in a prolonged fast.
If lack of glucose continues further, fat breakdown begins converting stored triglycerides into long chain fatty acids and glycerol. Most of these fats are directly used by the body for energy production. A part of it is converted by the liver to short chain keto acids, thus heralding ketoacidosis. These ketone bodies act as a back-up energy source for the brain.
Blood sugar levels are crucial
Manifestations of hypoglycemia
With a sudden fall in blood glucose levels, the body's counter regulatory mechanisms come in action and it tries to combat the falling blood sugar by a "fight-flight" reaction. There is release of adrenaline (autonomic response) causing-
- Increased heart rate (more number of beats per minute)
This is a natural protective response of our body giving indications to the individual that he or she should eat something to normalize blood glucose levels.
With severe and prolonged low blood sugar, the brain starts starving of glucose and symptoms of neuroglycopenia develop, which include-
- Clouding of vision
- Blunted mental acuity
- Loss of fine motor skill
- Abnormal behavior
- Convulsions or fits
- Loss of consciousness
When fall in blood glucose levels is gradual, then the early symptoms are masked and only the neurological abnormalities dominate the picture.
In diabetics the autonomic symptoms of tremor and hunger may not manifest due to nerve damage as a complication of prolonged diabetes or due to hypoglycemia unawareness.
Since the initial clinical signs of low blood sugar are dependent on adrenaline release, persons with long standing diabetes suffering from autonomic neuropathy loose the capacity to release this hormone.
Also, in the absence of neuropathy every episode of hypoglycemia makes nerves more insensitive, lowering the level of glucose required to trigger the response.
The end result is that potentially dangerous hypoglycemia is unrecognized and the defense against it is impaired.
Some people with insulin secreting tumors of pancreas also suffer from lowering of glucose threshold that triggers symptoms. In them also, blood sugar levels can drop very low before the person realizes it.
Warning signs of hypoglycemia
Low blood glucose is dangerous
- Hypoglycemia is defined as blood glucose level <70 mg/dl.
- Brain is vulnerable to this as it utilizes glucose as its sole source of energy.
- Early symptoms of low blood sugar are - sweating, tremor, increased heart rate, anxiety and hunger.
- Severe and prolonged low blood glucose leads to neuroglycopenia (headache, dizziness, confusion, convulsions and coma).
- Immediate glucose intake is essential.
- Small, multiple mini meals help prevent sharp fall in blood glucose levels.
Neuroglycopenia- brain function decline due to low blood glucose
Recognizable symptoms occur in persons without diabetes when the venous plasma glucose concentration falls rapidly below 45 mg/dl. This can easily be measured at home using a one prick glucometer device.
Even though overt symptoms are not present, subtle decline in neurological functions may start at minimal decrements of plasma glucose. Major central nervous system dysfunction may not develop until plasma glucose concentration approximates 20 mg/dl, because cerebral blood flow increases enough to deliver some glucose to the brain even when glucose levels are low.
Cerebral atherosclerosis or hardening and cholesterol deposits in blood vessels to the brain reduces elasticity and may compromise this mechanism.
People with poorly controlled diabetes may develop hypoglycemia symptoms at higher glucose concentrations than non diabetic individuals.
There is a rare condition that mimics neuroglycopenia in which blood glucose is normal but glucose levels in cerebrospinal fluid (the fluid that nourishes the brain) is low, owing to a defect in the glucose transport to the brain. Seizures and epilepsy like fits can occur in this condition.
This is defined as fall in blood glucose level in response to meals. The major conditions that lead to postprandial low blood sugar are-
- Alimentary hyperinsulinism - In persons who have undergone gastric bypass surgery due to any reason, the transit of food through the stomach into the intestines is very fast, leading to brisk absorption of glucose.
- Heriditary fructose intolerance and Galactosemia - Eating sweet fruits with a high content of fruit sugar fructose or intake of malt based drinks containing galactose, another simple sugar, causes fall in blood glucose levels in children with fructose intolerance or galactosemia.
- Leucine sensitivity - Intake of baby foods containing aminoacid leucine may cause fall in blood sugar in susceptible infants.
- Idiopathic hypoglycemia (cause unknown) - In true idiopathic hypoglycemia, after a heavy meal blood glucose levels fall and are accompanied by adrenergic symptoms (sweating, tremors, hunger). Such attacks occur spontaneously during everyday life and are relieved by ingestion of carbohydrates that raise blood glucose levels. Cause is not known.
- Pseudohypoglycemia - In this condition, symptoms suggestive of lowering of blood sugar appear 2 to 5 hours after a meal, but on testing blood glucose levels are normal. Many normal people experience similar symptoms at some point in their lives and may have even gained relief after eating. Patients with pseudohypoglycemia develop symptoms regularly and repetitively. Stress or anxiety is thought to be the main cause behind this condition. Mentally stressed or anxious people have enhanced adrenaline gush following a meal, or they may be abnormally sensitive to normal post meal adrenaline release.
Lowering of blood sugar occurs only after hours of fasting and is associated with an imbalance between production of glucose in the liver and its utilization by rest of the body. This happens in two major scenarios-
Underproduction of glucose
Inadequate production of glucose during fasting can be due to -
- Hormonal deficiencies - Lowering of hormones from pituitary and adrenal glands.
- Enzymatic defects - These occur mainly in children. Glucose-6-phosphatase deficiency, other liver enzyme defects and glycogen storage disorders are the main reasons.
- Substrate deficiency - This occurs in case of malnutrition due to inadequate food intake, muscle wasting states, chronic kidney failure and increased energy requirements as in late pregnancy.
- Liver disease - Liver being the main seat of glucose production during fasting, if gets damaged due to congestion, hepatitis, cirrhosis, hypothermia (lowering of body temperature) or uremia (excess blood urea in kidney failure), leads to low blood sugar levels.
- Medications and alcohol - Alcohol causes lowering of blood sugar only after a period of fasting sufficient to deplete liver glycogen stores. Oxidation of ethanol diverts liver activity towards itself and glucose production is blocked. Various medications like salicylates and blood pressure lowering medicine propranolol also lower blood glucose.
- Untreated malaria leads to hypoglycemia owing to malnutrition and liver damage.
Overutilization of glucose
This occurs in two main settings -
1. High blood insulin levels (hyperinsulinism)
Insulin is a hormone produced by specialized beta cells of pancreas that acts to lower blood glucose levels. When in excess it causes dangerous lowering of blood sugar levels. The reasons for insulin excess include -
- Insulin producing tumors (Insulinomas).
- Administration of insulin injections or anti diabetic medicines (sulphonylureas).
- Factitious hypoglycemia - Self induction of low blood sugar by deliberate injection of insulin or intake of anti diabetic medicine by a non-diabetic individual due to some psychiatric disturbance. This is common in medical personnel and relatives of diabetic patients.
- Insulin autoimmunity - Lowering of blood sugar and raised blood insulin due to antibodies to endogenous insulin. Some people develop insulin resistance and alternating hyperglycemia and hypoglycemia.
- Sepsis and constant infection in the blood - Toxins stimulate pancreas to produce more insulin.
2. Appropriate insulin levels
This occurs in various circumstances that include -
- Solid extrapancreatic tumors - Cancers like fibromas, sarcomas, hepatomas, cancers of intestines and kidney produce insulin like growth factors (IGF) that mimic insulin to lower blood sugar.
- Systemic carnitine deficiency - In this, levels of carnitine, a metabolite necessary to transport fatty acids to mitochondria (powerhouse of the cell) is low. As a consequence body organs including liver cannot utilize fatty acids as energy source and become solely dependent on glucose leading to its low levels.
- Cancer cachexia and fat depletion - In advanced cancer patients, all the body fat gets depleted, so is not available as an alternative energy source, so body only utilizes glucose causing its low levels.
Symptoms of low blood glucose
No early symptoms
Only delayed signs of brain dysfunction
Treat hypoglycemia immediately
Management of low blood sugar
In case of serious lowering of blood sugar producing confusion or coma, glucose should be immediately administered in intravenous form in bolus doses, followed by a constant glucose infusion until the person is able to eat a meal. Intake of carbohydrates by mouth is very essential, as liver stores of glycogen (the storage form of glucose) cannot be replenished with small quantities of intravenous glucose.
Early symptoms without neurological dysfunction can be treated at home with oral carbohydrates (orange juice, grapes, raisins, dates, glucose biscuits).
Lowering of blood glucose due to anti-diabetes medicines may last for days, and person may lapse back in coma if glucose infusions are stopped too soon.
Insulin secreting tumors necessitate surgical removal.
A high protein, low carb diet may relieve symptoms in persons with anxiety induced pseudohypoglycemia.
In case of reduced stomach size, the size of individual meals should be small and multiple mini meals should be had.
To prevent alcohol induced low blood sugar, avoid sugar mixers like gin and tonic or rum and cola and ensure supplementary food intake.
In normal circumstances, the food that we eat is digested in the intestines and glucose, aminoacids and fatty acids are absorbed in the blood. Excess of glucose is stored in liver and muscles as glycogen. When the blood glucose levels fall low this glycogen is converted back to glucose.
This mechanism is very crucial, as brain is solely dependent on blood glucose for energy. If blood glucose falls low, brain cells begin to starve and brain damage starts.
Early symptoms of low blood glucose are sweating, tremulousness, palpitations, anxiety and hunger. With severe and prolonged hypoglycemia, neurological dysfunction begins to show in the form of dizziness, headache, clouding of vision, blunted mental acuity and confusion.
Immediate emergency treatment with glucose is essential, else the person might suffer from loss of consciousness and even slip into coma.
I would request the readers to provide feedback and give their views and share their experiences with regards to hypoglycemia.
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