Why is the blood sugar sometimes so low? Those who understand what is happening to the body in cases of low blood sugar are in a better position to overcome it, and to avoid further cases in the future. 

Mild-to-moderate hypoglycaemia (low blood sugar) is one of the most common side effects of insulin therapy. In order to prevent mild case of low blood sugar from turning into a serious metabolic episode, one should be well trained and know how the body reacts to low blood sugar. 

Hypoglycaemia is the name given to cases in which the blood sugar drops to below 50 mg/dl (2.8 mmol/l). However, hormonal countermeasures start to set in much earlier, at around 65–70 mg/dl (3.6–3.9 mmol/l).

Mild hypoglycaemia can pass unnoticed. However, moderate hypoglycaemia can no longer be corrected by the sufferer. S/he needs help, but it can still be overcome with enough intake of carbohydrate. In cases of severe hypoglycaemia, the sufferer faints or can even fall into a coma that can be accompanied by convulsions. S/he definitely needs an emergency injection of glucagon or an intravenous infusion of glucose.  
 
Noticing the early signs
The list of possible signs of low blood sugar is long. Those who recognize their ‘own’ signs can quickly correct it with carb exchanges. How good one is at recognizing the signs of low blood sugar depends on, among other things, how well controlled the metabolism is generally. Those who often have low blood sugar are become desensitized.

The symptoms of hypoglycaemia are divided up into two categories, neuroglycopaenic and autonomic. Neuroglycopaenic symptoms result from a shortage of glucose in the brain, and autonomic symptoms result from regulatory mechanisms of the autonomic nervous system (see table). 

Whether or not one notices a drop in blood sugar is dependent upon how high the blood sugar was in the first place, and how fast it falls. If it plummets within a matter of minutes, the body will react more convincingly than if it falls gradually. In diabetics with generally bad metabolic control who are used to high blood sugar levels, a drop from 300 to around 150 mg/dl (16.7/8.3 mmol/l) will already be noticeable.

In addition, awareness of symtoms can be hindered for a certain time following a case of hypoglycaemia. Therefore, blood glucose awareness training is very important.  

Causes of hypoglycaemia

1. Enhanced insulin effect

• Insulin overdose
• Basal insulin that has not been well mixed
• Accidental injection of the wrong insulin (e.g. basal instead of rapid-acting)
• Injecting into the muscle instead of subcutaneously
• Too long a time span between injection and meal
• Rises in body temperature (e.g. a hot bath or sunbaking)

2. Not eating enough

• Reduced appetite, e.g. in cases of illness
• Overestimated carb exchanges
• Nausea and vomiting
• Alcohol intake without appropriate exchanges

3. Physical exertion
Those who exhaust themselves physically can experience a rapid or delayed (after a few hours) hypoglycaemia. Firstly, intensive physical exertion enhances insulin sensitivity, and more glucose is taken out of the blood stream. Secondly, the glucose availability from the liver is unhindered, because the active insulin is not cut down – as would be the case in people without diabetes.

A special situation can arise after sport, i.e., at midnight after having done sport that noon. Shortly after exertion, the blood sugar levels tend to be high due to the release of glucagon and adrenalin, to protect against potential low blood sugar. Hours later, this reaction subsides, and hypoglycaemia manifests. Hence, one should avoid over-correction with insulin in cases of high blood sugar after sport, and monitor the blood sugar more frequently thereafter.

Countermeasures
What does the body do to counteract hypoglycaemia? People without diabetes stop releasing insulin when the blood sugar drops too much. In people with diabetes, the insulin from the last injection continues to take effect. This can cause serious hypoglycaemia.

There are two further important regulatory mechanisms in which the body knows how to help itself in cases of low blood sugar. Firstly, more of the hormone, glucagon, is released. Secondly, more of the stress hormones, adrenalin and noradrenalin, are released. These hormones tend to raise blood sugar levels by triggering the release of glucose from sugar depots (glycogen) and stimulating glucose generation in the liver.

Already within a few months after diabetes manifests, inadequate quantities of glucagon are released. Consequently, the only way people with diabetes can counteract low blood sugar is through the release of adrenalin. High adrenalin levels give rise to autonomic hypoglycaemic symptoms. These symptoms, however, become weaker with repeated cases of low blood sugar. Hence, low blood sugar can become more and more difficult to notice. This raises the possibility of unawaredly falling into a severe case of hypoglycaemia. 

Nocturnal countermeasures
During sleep, the body is especially vulnerable to hypoglycaemia. The insulin sensitivity is generally higher than during the day, and the adrenal countermeasures are limited. Also, less cortisol –  another counteracting hormone – is released during sleep. Therefore, it is very important to choose the right nocturnal insulin and to administer it correctly, particularly in adolescents whose blood sugar tends to rocket in the early morning hours. This rise has to be effectively covered by the basal insulin – a deciding factor in good metabolic control.

There are signs that may point to nocturnal hypoglycaemia such as tossing and turning, a messed-up bed, nightmares, headache, tiredness and morning fatigue. These may indicate that the basal or late-night prandial insulins are being dosed too high.

Treating hypoglycaemia
The first thing that should be done in the presence of low blood sugar is to measure it. This is to check that the symptoms are really due to falling blood sugar and not something else. The next step is to take fast-acting carbohydrate (dextrose, sugared drinks) according to how low the blood sugar has fallen. If too much carbohydrate is taken, the blood sugar can rise too fast, requiring additional insulin that can, in turn, lead to another case of low blood sugar.

Therefore, a small amount of complex carbohydrate should also be eaten to prevent this rebound effect. Bread, for example, is especially suitable. 
In serious cases, however, one should not give anything to eat or drink. Instead, an emergency injection of glucagon should be administered. Children under 12 years of age should receive 0.5 mg (a half syringe), children over 12 years of age generally can have 1 mg (a whole syringe).

The glucagon takes effect within a few minutes. If necessary, a further injection can be administered after five to ten minutes. An emergency doctor can also administer a potent glucose intravenous infusion. After consciousness is regained, the child should receive something to eat and drink.

Children and adolescents with diabetes should:

• always have a supply of fast-acting carbohydrate (e.g. dextrose) at hand 
• measure blood sugar before and after any physical exertion – if necessary, to inject less insulin beforehand, or to take extra exchanges afterwards. 
  

Parents or guardians should:

• have an emergency glucagon injection on hand, and know how to use it, in cases of severe hypoglycaemia
• know the important emergency telephone numbers by heart.

The consequences
What long-term effects do frequent bouts of mild hypoglycaemia or the occasional case of severe hypoglycaemia have? It is possible, albeit not in all cases, that cognitive ability (attention span, learning ability, creativity) is affected. The brain of small children is particularly dependent on glucose for its development. Hence, it is very important to avoid low blood sugar. 

Rarely, severe hypoglycaemic episodes can trigger neurological disorders such as lameness. These are, however, mostly reversible. Only in very extreme cases can a severe case of hypoglycaemia lead to death (the so-called dead-in-bed syndrome). Fortunately, this phenomenon hardly ever affects adolescents under 19, and doesn’t exist at all in small children with type 1 diabetes.

Symptoms of Hypoglycaemia
Autonomic symptoms: Trembing Paleness Awkwardness Rapid pulse Fear Sweating Hunger Restlessness	Neuroglycopaenic symptoms: Confusion Tiredness Fatigue Dizziness Nervousness Hot flushes Mood swings Difficulty to speak and think Headache Faintness Loss of consciousness Convulsions

---

Claudia Nestoris MD
Please direct all enquires to the publishers
E-Mail: finkenauer(at)kirchheim-verlag(dot)de