Blood Glucose & Ketones How & When to Check
Monitoring is a critical part of diabetes management. If your child has type 1 diabetes, you (and your child, as age-appropriate) will need to monitor their blood glucose and check for ketones.
Blood Glucose Monitoring
Blood Glucose testing involves obtaining a small drop of blood (via a finger-prick) which is then applied to a test strip and analyzed with a blood glucose monitor.
How to Perform a Blood Glucose Check
- Both fingertips and the ends of the toes may be used to obtain a blood sample for testing.
- Always wash your hands and have your child wash his or her hands before doing a blood glucose check. If there are even small amounts of sugar on your fingers or your child’s fingers/toes, the sample may be contaminated. If you get a false high reading, you may give a correction dose of insulin that is not needed, or is higher than needed, which could result in low blood glucose later.
- Soap and running water is the recommended method of hand-washing. However, when this is not possible (ex. when you are away from home/traveling, or when your child is sleeping) hand wipes or alcohol wipes may be used to clean the testing area. When using alternate methods of cleaning, take the results “with a grain of salt”, and if there is any doubt as to their accuracy, re-check before administering a correction dose of insulin.
- Although it is necessary to clean the test site (finger or toe) before testing, it is not necessary to disinfect the area using alcohol wipes. (Alcohol wipes may be a handy tool for cleaning when soap and water are not accessible, but they are not superior to non-disinfecting hand wipes.)
- Hold the lancing device flush against the skin and push the button to cause the lancet to pierce the skin. Hold the end of the test strip against the blood drop, allowing it to draw the blood up into the strip. Holding the test strip parallel to the skin surface usually works best.
- If a drop of blood is obtained that is too small for testing, don’t squeeze the end of the finger or toe in order to increase the size of the drop of blood. If you squeeze too hard, interstitial fluid may be forced into the sample, resulting in a false reading. If there is not enough blood, it is much better to “milk” the finger (intermittently squeeze the finger close to the hand/foot, working towards the drop of blood at the tip).
Tips from the Trenches
If we use my son’s finger to check blood glucose, and find high blood glucose when we have only “questionable” cleaning methods at our disposal, we re-check using his toe, which is less likely to be contaminated with sugar.
When Should Blood Glucose Be Checked?
- Check the blood glucose at least 4 times a day, before meals and the bedtime snack. Adequate BG management may be attained if you are checking BG at this minimum level. For a greater level of control, when caring for younger children (who cannot report symptoms of high or low BG), and in times of activity, illness, or other changes in routine, it will be necessary to check BG more than 4 times a day.
Tips from the Trenches
To stay on top of things, both of us have found it helpful to check our sons’ BG 8-10 times a day on a regular basis.
~Danielle and Michelle
- You may also need to check in the middle of the night if you suspect your child is having lows overnight, or if the bedtime reading is low. It is a good idea to check periodically, even if you have no reason to suspect lows. Repeated undetected lows will deplete your child’s liver stores of glycogen, which will put him or her at higher risk of a severe low.
- It is usually recommended to wait at least 2 hours after eating carbohydrates before you check blood glucose. If your child’s routine does not allow a two-hour gap, discuss this with your diabetes nurse or dietician.
- Record the blood glucose in your child’s diabetes log book. Also record the insulin dose and make a note about level of activity, stress, illness, special occasions, medications, and changes from your child’s regular meal habits.
- You may want to keep a paper record, even if you download data from the meter. This allows you to see patterns of high and low blood glucose in real time, and then to make timely adjustments to insulin doses.
- The results of blood glucose checks provide important information to guide short and long term decisions about your child’s diabetes care.
- Aim for blood glucose between 4-7 mmol/L before meals and the bedtime snack. Younger children and those that cannot detect low blood glucose will have a higher target of 6-10 mmol/L.
- Do not panic if one blood glucose reading is high or low. Look for patterns in the logbook. If you see a pattern of high blood glucose, or if your child has more than two lows in a week, call your diabetes nurse to have the insulin dose changed.
Ketones are the by-products of the burning of fat as fuel, when there is not enough of either glucose or insulin to support the normal process of burning glucose for energy. In other words, if the blood glucose is high, the body may start to burn fat for energy. If fat is burned, ketones are produced. A large amount of ketones can harm the body.
Therefore, when there is a reason to suspect the presence of ketones, it is important to check the urine and/or blood.
Always check for ketones when:
- The blood glucose is greater than 14.0 mmol/L.
- Your child is ill.
- Your child is nauseous or has vomited.
- Your child has a stomach ache.
Checking Ketones: Urine vs. Blood
You may check for ketones in either the urine or in the blood. (Note that blood ketone testing is more precise than urine ketone testing.)
Urine Ketone Testing
Urine ketone testing involves obtaining a sample of urine and then dipping a urine ketone test strip into that sample.
Common urine ketone test strips include:
- Test for the presence of ketones in the urine.
- Accurate testing requires that the strip be compared to a sample colour gradation almost exactly 15 seconds after urine is applied to the test area.
- If you want to verify the results, you need to supervise at the time of testing – if too much time elapses after the test strip is dipped in the urine, there may be a high rate of false-positives (strip seems to indicate a higher level of ketones than are actually present).
- The strips expire 6 months after opening the bottle.
- Chemstrip® uG/K
- Test for the presence of both ketones and glucose in the urine.
- Accurate testing of ketones is achieved at 1 minute or more. This greater window of time is useful if you would like your child to test their urine independently, without you being present at the time – you can verify the results by looking at the strip several minutes later without worrying about an over-representation of false-positives.
- These strips may also be useful for detecting the presence of glucose. Although this is not particularly useful for a child with diabetes (we already know they may have glucose in their urine), it may be useful for occasional testing of siblings (or for testing drinks in restaurants to confirm that you actually received the diet pop you ordered!)
- The expiry date is listed on the bottle and, if stored properly in the original container, the strips will be reliable until this date.
The strip will turn PINK or PURPLE if your child has ketones. (Some products also measure glucose in the urine and the strip will also turn green or brown.).
Tips from the Trenches
When my son was an infant, we used urine for all ketone checks. If we wanted to test for ketones, we would place a cotton ball in his diaper and wait until it was saturated with pee, then squeeze the urine out of the cotton ball onto the strip. This worked well in many cases, however we had problems if we hadn’t anticipated the need for a ketone check and so had not placed a cotton ball in his diaper, or if he was dehydrated as a result of illness and so was not peeing much, or if the cotton ball moved in his diaper and so did not get wet when he peed. For these reasons, we found blood ketone testing more convenient.
Blood Ketone Testing
Blood ketone testing involves obtaining a small drop of blood (via a finger-prick, just as in blood glucose monitoring) which is then applied to a special blood ketone test strip and analyzed with a blood ketone monitor.
One blood ketone testing monitor available in Canada is the Precision Neo™ (Abbott Diabetes Care). It also tests blood glucose using the same monitor. Abbott also makes the Freestyle Libre which, in addition to being a Flash Glucose Monitor, also performs ketone tests (with the correct strips).
Pros of Blood Ketone Testing (compared to urine ketone testing):
- More precise. A blood ketone tester gives an actual number, in mmol/L. This number is reported in tenths of a unit (ex. 1.7 mmol/L).
- More current measure. A blood ketone test reports the amount of ketones that are currently in the blood; there is a 2-4 hour delay for urine ketone testing.
- Less subject to testing errors.
- Longer time to the expiration date than urine strips, as each blood test strip is individually foil wrapped.
- Can be performed anytime, anywhere, without having to obtain a urine sample. This is particularly useful when you are out in public, or when your child is sleeping. To perform a blood ketone test, you do not have to wake your child to have them pee.
Cons of Blood Ketone Testing (compared to urine ketone testing):
- More expensive than urine testing.
- Testing involves a finger-/toe-prick, which may be distressing for some children.
- A separate strip is needed to do a ketone check (you cannot use a blood glucose test strip for ketone testing).
Quantity of Ketones
When you perform a ketone test using blood or urine, results will show the absence or presence of ketones in varying degrees, as follows:
|Negative (trace)||less than 0.6|
|+ (small amount of ketones)||0.6 – 1.4|
|++ (moderate)||1.5 – 3.0|
|+++ (large)||greater than 3|
If testing reveals that ketones are present at more than trace levels, AND blood glucose is high, your child needs extra insulin.
For more information about how much extra insulin, contact your child’s diabetes health care team. You may also want to check out some other articles on this site:
Care of Monitoring Supplies
- Blood and Urine test strips should be stored in their original container.
- Protect blood and urine test strips from light and moisture. Do not leave test strips or your meter in the car where they will be exposed to very hot and cold temperatures.
- Do not use test strips after the expiry date. Check the package insert for instructions on how properly to use, and when to dispose of, blood and urine test strips.
- Make sure that you receive instructions on how to use your meter. Not coding it properly (for those that require coding – many of those currently on the market do not) or using too small of a drop of blood on the strip can give false results. Have a lab-to-meter comparison done when you buy a new meter and every six months thereafter. (This lab-to-meter comparison can be done at the same time as A1C testing or other regular lab blood work. A fingerstick plus drawing blood from a vein (arm) will be required. You may choose to provide the blood samples yourself, instead of your child, for the purposes of the lab-to-meter comparison only, if your child is not having blood drawn from a vein.)
- Do not let anyone else use your child’s blood glucose monitor or lancet device, as blood transmitted diseases can be spread by sharing equipment.
The above information was adapted with permission from The Alberta Children’s Hospital Diabetes Clinic information handouts.
The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.
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