Self monitoring of blood glucose (SMBG)
The urine glucose tests indicate very roughly and indirectly the blood glucose levels. The standard blood glucose/sugar tests already mentioned can be performed only in a laboratory. Blood glucose/sugar thus estimated once in two to three months cannot give an idea of day to day fluctuations in blood glucose level. With recent advances in technology, self-testing of blood glucose has become a practical proposition. With this technique, it is possible to achieve a better control of diabetes by adjusting food intake, exercise and medication. It facilitates flexibility in life style.
The essentials of the technique of SMBG
Prick the side of the finger tip (and not the ball of the finger) for a drop of blood. (Fig.3). Place the drop of blood on a chemically treated pad on the test strip. Wait for the prescribed length of time. Remove the blood from the test strip. Wait for another length of time. Some strips can be compared visually with the colour chart provided with the kit. Some strips are put into a meter for automatic reading of the blood glucose level (Fig. 4). The meter eliminates errors of individual judgment, unconscious bias and is especially useful for people with visual problems. All meters are accurate within ± 10 per cent.
The blood glucose is measured as mg/dl (dl is a short form of decilitre, that is, one tenth part of a line or 100 ml).
Many people find getting a good drop of blood difficult. To get a good drop of blood, warm your hands in hot water but dry them afterwards. Squeezing the finger above the last joint also helps. After pricking the finger, turn the hand over, so that the palm faces the floor and the drop of blood hangs from the finger. With some glucometers, blood samples can now be taken from arm, forearm and abdomen.
Even those who can afford to possess a meter should not look at it as a fancy gadget. To be really meaningful, self blood glucose monitoring, may have to be done several times a day, that is fasting, before and after meals and at bedtime. The patient should note down the pattern of blood glucose levels and adjust the diet, insulin dose and the exercise, on the basis of this knowledge. The diabetic has to be well informed and knowledgeable in order to make the best use of this technique.
The following points to be noted before ordering a meter:
- Is after sales service available?
- Is the instrument factory calibrated?
- Time needed for calibration
- Does the instrument contain a buzzer? This is useful for those with a poor vision .
- Range of blood glucose
- Memory
- Price whether inclusive of strips
- Period of guarantee
- Whether the required test strips are locally available.
- Whether the battery is replaceable or disposable
While computing the cost of SMBG, one should take into account the cost of the test strips, the meter and of the finger pricking device.
Importance of SMBG
Blood glucose tests using glucometers are accurate. It helps to adjust insulin dose, diet and exercise and to correlate blood glucose level with the sense of well being. It reduces hospital admissions.
Its disadvantages are discomfort of pricks and the cost. Nowadays, glucometers available in India are priced from Rs. 1500 onwards.
The SMBG is especially useful in the following types of diabetics: those who have been advised to achieve a tight control of diabetes, for instance, during pregnancy, those who get frequent low blood glucose reactions especially without any warning, those with an unusually high or low renal threshold for glucose, those who need an unusually large dose of insulin and those on insulin pumps.
SMBG is not very necessary for those well controlled by diet or oral drugs.