Even though it may be tiresome, taking individual responsibility for one’s diabetes, and for the timely monitoring of blood sugar, was still an unreachable dream a few decades ago. Knowing exactly why the blood sugar should be measured provides a good incentive. Claudia Nestoris explains the basics of self-monitoring.  

In many families, the daily routine of measuring blood sugar is regarded as a necessary evil. The children often have to be reminded again and again to do so, and bang! … there bursts the balloon of domestic bliss. 
The reasons as to why monitoring is so important, however, are many. Well recorded values are essential for extracting much needed information.  

Measuring
The gold standard for taking individual responsibility for one’s diabetes is self-monitoring. With relatively little ado, one can obtain an insight into the metabolic patterns of the previous 5 to 15 minutes. And! these readings are very easy to interpret. 

With single-value blood glucose monitoring (as opposed to continuous blood glucose monitoring), the glucose concentration is measured from the blood in the capillaries in the tip of the finger or in the ear lobe. The capillaries are minute blood vessels that contain the blood on its way from the large arteries back to the veins. The blood sugar level in the arteries is around 8% higher than in the veins. The value in the capillaries lies exactly in the middle and, therefore, offers a good picture of the glucose level just after it has reached the cells. 

In days gone by, single measurements used to be taken using a test strip on which a drop of blood was deposited. The resulting colour was matched with a colour scale. This method has been rendered all but obselete through the invention of modern glucose meters. 

Modern glucose meters provide comparatively reliable readings, but may veer from the true laboratory values by anything up to 15%. One study has shown that around half of the meter readings can overstep this accepted variation factor significantly. The reasons for this are dependent on factors such as temperature, moisture, oxygen levels, lipid levels, or changes in blood constitution.

The meter readings, although extremely valuable for providing information on the current blood sugar situation (stable, too high or too low), are not 100% exact. The superfluous practice of using several devices to compare readings, however, is certainly not recommended, and only serves to confuse matters.

When and how?
In answer to the question, “How often should I measure?”, one needs to find the compromise between what would be the ideal to achieve the strictest metabolic control possible, and what would be at all feasible in practice. One must remember that the blood sugar is in a constant state of fluctuation and that each meter measurement provides only a momentary blood sugar reading.

This is why one cannot draw any meaningful conclusions from readings that lie too many hours apart. If one compares, for example, four equally-spread single measurements to a continuous profile, one can see that between two acceptable meter readings, the blood sugar level can rise, unnoticed, to levels way above the norm. Only in the next HbA1c measurement will this show up.
Ideally, measurements should be taken before breakfast, before lunch, before dinner, before going to bed, and before each snack.  

What exactly does each measurement tell me?
Firstly, the early-morning measurement on an empty stomach tells you how well the long-lasting nocturnal insulin worked throughout the night. If the values are repeatedly high, it is not enough to merely correct it with a fast-acting insulin, but to add an extra injection of nocturnal insulin at around 10:00 to 11:00 pm.
Secondly, the reading taken before each snack should lie around two hours after the previous main meal and are, therefore, very useful in telling you whether the amount of insulin you administered for that main meal was correctly chosen. If these particular readings are constantly too high or too low, the carb factor should be reconsidered. If they are only sporadically out of kilter, an additional injection of rapid-acting insulin analogue can be administered for corrective purposes.

Thirdly, the readings before each main meal provide information on the effectiveness of the basal insulin that was administered at the previous meal—provided that the between-meal values were okay. If the readings before each main meal are constantly too high, one needs to take more basal insulin. Beware of this solution, however, if an unaccounted-for snack was had, or the carb factors were incorrectly calculated.

Fourthly, the readings around 10:00 to 11:00 pm usher in the night. Here, the readings are allowed to lie somewhat higher than during the day (approx. 140 mg/dl or 7.8 mmol/l). If this reading is unstable, however, or a rise in the nocturnal insulin to be expected, an additional measurement at around 2:00 am is recommended. This is the time when insulin sensitivity is at its highest, making the likelihood of hypoglycaemia at its greatest.

It goes without saying that more measurements than mentioned above should be taken to allow for special circumstances, for example, before and during swimming or sport, during times of illness, during times of unusual effort, or any other variations from the daily routine.

On average, each patient on intensified conventional therapy (ICT) should make around six measurements a day. Those wearing pumps should measure slightly more often. A technical defect, for instance, could lead to a shutdown of the insulin supply, including the basal insulin, which could rapidly lead to an acute insulin deficit and perhaps ketoacidosis.

The reason for recording readings
Many children think that the sole purpose of recording the blood sugar readings is to have something to hand in to the doctor at the next visit to the clinic. 
Indeed, the recorded readings are a must for discussions on tailoring therapy. More importantly, they enable the family to recognize repeated tendencies and to make decisions accordingly, or to seek the advice of the family diabetes specialist. The recorded readings are especially transparent when measurements are taken at exactly the same time for several days (eg, a week), and listed vertically on top of each other.

In this way, blood sugar tendencies are easily recognizable, making it simple to adjust the dosages accordingly. Keeping a record of the readings is usually a matter for the parents at least until the child reaches school age. However, even after this time, the parents should take an interest in the readings, otherwise the adolescent may quickly become tired of making them. The measurements will only be taken intermittently, rendering them useless for analysis. In the worst case, the measurements might no longer be taken at all. 

Contact:
Claudia Nestoris MD
Kinderkrankenhaus auf der Bult
Hannover
E-Mail: nestoris@hka.de