CAUSES OF HYPOGLYCAEMIA
WHY DOES BLOOD GLUCOSE FAL?
Delay and omission of meals
The most common cause of hypoglycemia is delay or omission of a meal. A diabetic, taking insulin or oral drugs should have uniform and regular meals. The peak action of intermediate acting insulins occurs about 8 hours after the injection. Hence a diabetic taking these insulin preparations before breakfast, should have a carbohydrate containing snack, for example, a slice of bread or two biscuits or a fruit portion at 4 p.m. The peak action of short-acting insulins occurs 2 to 3 hours after the injection. Hence a diabetic taking these preparations before breakfast should have a mid-morning snack. Diabetics taking insulin before supper should have a snack at bedtime.
Excess of insulin
Current insulin treatment, at its best cannot imitate nature exactly. There is often excess of insulin in between meals and at night.
The blood glucose level falls if insulin is given in excess. This may happen due to an incorrect measurement of insulin dose, that is, using U100 instead of the usual U40 insulin, using a wrong syringe, following a wrong scale on a syringe or injecting insulin mixture in wrong proportion. A diabetic advised to inject regular insulin 10 u and intermediate-acting insulin 20 u may inject inadvertently regular insulin 20 u and intermediate-acting 10 u. An excess of insulin may be administered during an adjustment of insulin dose. The insulin requirement falls after an infection is controlled, post delivery, or after discharge from a hospital. Insulin is absorbed more completely if it is injected into a new area or over exercising muscles or if injected into a muscle. Hence, hypoglycaemia may occur if the site of insulin injection is changed from a frequently used part to a little used part, or if insulin is injected into a thigh and the person runs or jogs after the injection. Mistakes in measurement of insulin dose can occur if the person has a defective vision.
Reduction of weight
The insulin requirement diminishes if a diabetic loses weight. A diabetic may develop hypoglycaemia if the same dose of insulin is taken even after losing weight.
Oral Drugs
The oral drugs of the Sulphonylurea group can produce hypoglycaemia. The hypoglycaemia produced by chlorpropamide and glibenclamide lasts longer than the one produced by the short-acting drugs like tolbutamide and glipizide.
Alcohol
Alcohol can produce hypoglycaemia by impairing the function of the liver to produce glucose.
Hypoglycaemia unawareness
Hypoglycaemia will occur if a diabetic has long intervals between meals. A snack should be taken at 7 p.m. if there is a long gap between the tea time snack and supper.
Warning signals enable the person to take appropriate action, like taking glucose, to prevent full blown hypoglycaemia. Sweating and trembling are early signals of hypoglycaemia. These warning signals may be absent in long standing diabetes, in those taking certain drugs for high blood pressure (beta blockers), those taking alcohol, those having repeated hypoglycaemia and those with involvement of autonomic nervous system. Alcohol inhibits production of glucose by liver and reduces trembling, a warning sign of hypoglycaemia. Total hypoglycaemia unawareness can create problems in day to day life and continuing in certain jobs.
Such persons and their relatives should watch for subtle signs of hypoglycaemia. Self blood glucose monitoring is very useful in such cases. Hypoglycaemia unawareness may be corrected by avoiding strictly, episodes of hypoglycaemia for 4 weeks.
When to expect hypoglycaemia ?
Hypoglycaemia due to insulin occurs at the time of its peak action but hypoglycaemia can occur within one to three hours of insulin injection. Insulin may be absorbed fast after an intramuscular injection. Hypoglycaemia due to long-acting sulphonylureas like chlorpropamide or glibenclamide can occur any time of the day. Chlorpropamide taken on a previous day can cause hypoglycaemia the following day.
Blood and urine tests
The blood tested during hypoglycaemia shows a low blood glucose level. The sample of blood should be collected before glucose or sugar is administered. The urine may contain sugar during hypoglycaemia, since the urine collected was actually produced earlier when the blood glucose level was normal or high. But urine produced after the bladder is emptied does not contain sugar.