Monitoring and Control: Urine and Haemoglobin a1c
Today let’s talk about how to monitor the level of haemoglobin and urine, and we asked a few questions on these topics.
URINE
What does it mean if I have a lot of ketones but no glucose on urine testing?
Testing for ketones in the urine can be rather confusing and, unless there are special reasons for doing it, we do not recommend it for routine use. Some people seem to develop ketones in the urine very readily, especially children, pregnant women and those who are dieting strictly to lose weight.
Usually if glucose and ketones appear together it indicates poor diabetes control, although this may pass off quickly so that glucose and ketones, present in the morning, may disappear by noon. If they are both a permanent feature, your diabetes needs to be better controlled, probably by increasing the insulin dose.
On rare occasions, ketones may appear in the urine without glucose. This is most likely to be found in the first morning specimen and probably occurs because the insulin taken the previous night is wearing off. Under these circumstances it is not serious and no action is needed.
Finally, ketones without glucose in the urine are very common in people who are trying to lose weight through calorie restriction. Anyone on a strict diet and losing weight will burn up body fat, which causes ketones to appear in the urine. Provided that there is no excess glucose in your urine, these ketones are of no concern and probably indicate that you are losing weight by breaking down body fat.
For some time now I have suffered from diabetes. I am curious to know what type of tests are made on my urine specimens when they are taken off to the laboratory.
Urine specimens are tested for several things but the most common are glucose, ketones and albumin (protein). These tests serve only as a spot check and are meant to complement your own tests performed at home. Clinics still tend to test the percentage of glucose in urine samples, even though the HbA1c is a much better guide to diabetes control. The detection of ketones is of rather limited value since some people make ketones very easily and others almost not at all, but the presence of large amounts of ketones together with 2% glucose shows that the diabetes is very badly out of control.
The presence of protein in the urine can indicate either infection in the urine or the presence of some kidney disease, which in people with diabetes is likely to be diabetic nephropathy, a long-term complication. A more recent test is for microalbuminuria; the test detects microscopic amounts of albumin in the urine and can show signs of very early kidney damage.
HAEMOGLOBIN
A1c
When I last went to the clinic, I had a test for haemoglobin Ale. What is this for and what are the normal values?
Haemoglobin Ale is a component of the red pigment of blood (haemoglobin A, or HbA) which carries oxygen from the lungs to the various organs in the body. The HbA1c is calculated as a percentage of total haemoglobin and can be measured by a variety of laboratory methods. HbA1c consists of HbA combined with glucose by a chemical link. The amount of HbA1c present is directly proportional to the average blood glucose during the 120-day life span of the HbA-containing red blood corpuscles in the circulating blood.
The test for HbA1c is the most successful so far developed to give an index of diabetes control. The blood glucose tests, which we have used for many years, fluctuate too erratically with injections, meals and other events for an isolated sample taken at one clinic visit to provide much information about overall control. HbA1c averages out the peaks and troughs of the blood glucose over the previous two to three months.
Normal values vary a little from one laboratory to another and this can be a source of confusion as results from different clinics cannot be compared directly without the normal range known for each particular laboratory. (Diabetes UK is trying to correct this anomaly.) Normal values usually run between 4.5% and 6.1%, but you must check the normal range for your own laboratory. In someone with poorly controlled diabetes, or in whom diabetes is recently diagnosed, the value of HbA1c may be as high as 15%, which reflects a consistently raised blood glucose over the preceding two to three months. If control is good, the HbA1c will be in the target range of 6.5-7.5%, while someone who runs their blood glucose levels low by taking too much insulin may have a subnormal value, that is, below 6%. There is a move to change the way HbA1c is reported from a percentage of haemoglobin to the new units called mmol/mol. The target range will be less than 48, which is the equivalent of less than 6.5%. To help with the change over, most laboratories will report the HbA1c both as a percentage and in the new units.
I’ve just had a fructosamine test but I didn’t like to ask what this was for. What is this test?
Fructosamine is the name of a test that is similar to HbA1c in that it indicates the average level of glucose in the blood over a period of time, in this case the two to three weeks before the test is done (compared with the preceding two to three months for HbA1c). It measures the amount of glucose linked to the proteins in the blood plasma (the straw-coloured fluid in which the red cells are suspended): the higher the blood glucose concentration, the higher will be the fructosamine. Its advantages are that it is usually quicker and cheaper for the laboratory to do. The normal values may vary from one laboratory to another depending on the way the analysis is performed; in general, a value of less than 300 micromol/litre is a typical laboratory’s normal value. In order to make sure you don’t get confused, we suggest that you pay particular attention to what is done in your clinic; please don’t hesitate to ask and make quite sure you do know what is going on.