Troubleshooting Guide for bg highs & lows
If you have ever been overwhelmed by the seemingly endless array of variables that affect blood glucose…
If you have ever responded to one of your child’s blood glucose checks with the thought, “Where did THAT come from?!”…
… then you may want to explore the following guide to some of the possible reasons for out-of-range blood glucose results.
(Note: Items marked with a “P” apply specifically to insulin pump users.)
| Possible Causes of ONE-OFF Highs/Lows | |
|---|---|
| PHYSIOLOGICAL CAUSES | |
| High Blood Sugar | Low Blood Sugar |
| Was your child's glucose low recently ? In response to a low BG, the liver may release a large amount of stored glucose ("glycogen"), ultimately resulting in high glucose. | Was your child's glucose low recently ? For the 12 – 24 hours following a low, there is an increased probability of another low. |
| Did anything happen that could have stressed or scared your child? Like a test at school, an argument with someone, having a tantrum, or watching a scary movie/TV show. Stress and anxiety can cause glucose to rise. Did your child participate in an exciting activity today? For example, amusement park rides, or videogames. Stress, even when it's positive stress, tends to cause glucose to rise. | Did anything happen that could have stressed or scared your child?Like a test at school, an argument with someone, having a tantrum, or watching a scary movie/TV show. For some people with T1D, stress and anxiety cause glucose to fall. |
| Did your child have an athletic game or competition? Like a hockey game, track and field sprints, gymnastics competition, or HIIT? Physical activity that is competitive or anaerobic in nature tends to increase blood glucose levels. | Was there unplanned physical activity, or was there more exercise than usual? Physical activity tends to lower blood glucose levels. |
| CAUSES re: FOOD | |
| High Blood Sugar | Low Blood Sugar |
| Were recent carbs counted correctly? Did you have to wildly guess at the carb content of anything? Did your child eat any new foods? Eat out? Have a treat that he doesn’t usually have? Under-estimating carbs leads to under-dosing of insulin for those carbs, which leads to high BG. | Were recent carbs counted correctly? Over-estimating carbs leads to over-dosing of insulin for those carbs, which leads to low BG. |
|
Was the insulin dose for food actually given? Was the complete bolus delivered? Did she have seconds that she forgot to bolus for? If using a pump remote, did the signal transmit from the monitor to the pump? |
Was the last snack/meal double-dosed? (Ask your child, or check the pen, or check the pump bolus history.) If so, she received too much insulin for the food she ate, resulting in low glucose. (When we hadn’t completely passed over responsibility for insulin delivery, more than once we gave insulin via our son’s remote AND he gave insulin straight from his pump without realizing that we had already done so!) |
| Did your child over-treat a low blood sugar ? If your child eats more fast-carbs than are needed to effectively treat a low , their BG may rebound to the high end. | Did your child under-treat a low blood sugar ? If your child doesn’t eat enough fast-carbs to effectively treat a low , their BG may stay in the low range, or come up briefly only to dip down again. |
| Was the last meal high carb? High on the Glycemic Index (GI) ? Blood glucose may spike soon after a meal/snack that contains lots of carbs, especially if those carbs digest quickly (high GI). In this case, the food gets in ahead of the insulin, resulting in high glucose. | Was the most recent meal/snack low on the Glycemic Index (GI)? Giving all required rapid-acting insulin upfront with foods that digest slowly (low GI) can cause a low soon after eating, because the insulin gets in before the food. |
| Did your child recently eat high fat food?High fat foods digest slowly, so there is still food being converted to glucose in the body, even after insulin has subsided. High fat foods also cause insulin resistance several hours after eating them, so the high BG may show up much later. | Did your child recently eat high fat food? High fat foods digest slowly, so when all the required rapid-acting insulin is given upfront, the insulin gets in before the food, causing low glucose. |
| Did your child recently eat a high protein meal?Eating protein in the relative absence of carbs will raise blood glucose, as the body converts protein into glucose for fuel when the preferred fuel-source, carbohydrates, is not available. | |
| CAUSES re: INSULIN | |
| High Blood Sugar | Low Blood Sugar |
| Is the clear insulin cloudy?Has the cloudy insulin clumped? These are signs that insulin is no longer effective. | |
| Has the insulin expired or been in use longer than a month? Again, the insulin may no longer be effective. | |
| Has the insulin been exposed to extreme temperatures?Insulin doesn’t work well if it’s exposed to heat or to freezing temperatures. | |
| How long has the insulin been in the pump? Insulin and plastic don’t play well together, so to keep your insulin working well it should be changed every 2-3 days. | Was the cartridge recently filled with fresh insulin? If you were previously using ineffective insulin and dialed up the dosing to get results, then when you switch to insulin that works well, you may experience more lows. |
| CAUSES re: THE INJECTION / INFUSION SITE: | |
| High Blood Sugar | Low Blood Sugar |
| Are there bumps or lumps at the injection / infusion site? This may indicate scar tissue, which hampers absorption of insulin, causing high BG. | Did you switch from a favourite, over-used site that had developed a lump (a lipohypertrophy)? Absorption will improve when using a “fresh” injection / infusion site, which may lead to lows. |
| Is there redness or irritation at the injection / infusion site? This may indicate infection or a reaction that hinders absorption, leading to high glucose. | Was a new injection / infusion site used, that you haven’t used previously? Some parts of the body absorb insulin better than others. |
| Was the body part with the injection / infusion site heavily exercised? For example, did your teen do bicep curls while his infusion set was on his arm? Or do leg work and then inject insulin into his thigh?If so, insulin may absorb more efficiently than the same activity with an injection into a non-exercised body part, resulting in lows. | |
| Has the infusion set been in longer than recommended?After a few days, the body tries to “heal” the area around the cannula, decreasing insulin absorption and leading to highs. | Was a new infusion set just inserted? The body has not yet started to “heal” around the cannula, so insulin is delivered efficiently. |
| Is there any blood at the infusion site or in the pump tubing?Don’t panic – it just means that the insertion may have hit a blood vessel. Insulin is absorbed most efficiently into the fat layer of the skin; if the cannula is sitting anywhere else, insulin absorption may be compromised. | |
| CAUSES re: THE PUMP | |
| High Blood Sugar | Low Blood Sugar |
| Is there air in the pump tubing or cartridge? Is the pump tubing filled/primed? Was the pump re-primed after disconnecting (if applicable)? Did you remember to fill the cannula when you changed the infusion set (if applicable)? Gaps of air in the system may interrupt the flow of insulin, leading to high BG. | |
| Is the infusion set still securely attached? Is the connection snug between the tubing and the cartridge? Are there any leaks in the tubing or at the connection to the cartridge? (You may smell insulin, or find a tissue wet after you run it along the tubing or cartridge.) High glucose is likely if even a small amount of insulin isn’t getting from the pump to the body. | |
| Any recent pump alarms or warnings? If your pump has an occlusion (blocking insulin delivery) or has mal-functioned in some way, then high glucose may result from a lack of insulin. | Could a young child have “played” with the buttons on their pump, inadvertently delivering insulin? Check the pump history to rule out this possible cause of low glucose. |
| Are the pump batteries very low or dead? Without enough power, the pump cannot work effectively. | |
| Is the date and time set correctly on the pump? If the time wasn't updated before/after Daylight Savings Time, then your hourly rates and ratios may not be in sync with your body's needs. | Is the date and time set correctly on the pump? If the time wasn't updated before/after Daylight Savings Time, then your hourly rates and ratios may not be in sync with your body's needs. |
| Is the pump cartridge empty or low? No insulin = no coverage for food and correction of highs. | |
| Possible Causes of a PATTERN of Highs/Lows | |
| High Blood Sugar | Low Blood Sugar |
| Does your child have any symptoms that may indicate they are getting sick? Blood glucose can be quite unpredictable before, during and after an active cold, flu or virus (like covid). You may need to manage diabetes differently when your child is sick . | Does your child have any symptoms that may indicate they are getting sick? Blood glucose can be quite unpredictable before, during and after an active cold, flu or virus (like covid). You may need to manage diabetes differently when your child is sick . |
| Was your child less active than usual over the last day or so? Your child's body uses insulin less efficiently when they are less active than usual, so glucose levels may be higher than usual, even if the amount of insulin they receive hasn’t changed. | Was your child more active than usual over the last day or so? Your child's body uses insulin more efficiently when they are more active than usual, so glucose levels may be lower than usual, even if the amount of insulin they receive hasn’t changed. |
| Could your child be going through a growth spurt? You may notice that their pants are suddenly too short, or that BG is often elevated a few hours after bedtime (when growth hormone is released).Insulin needs increase as kids grow. | |
| Has the season changed recently? (From winter to spring; from spring to the heat of summer, etc.) At these times, activity levels change, insulin may need to be stored differently to remain effective, and there seems to be some effect that is independent of activity and insulin. For reasons that we can’t explain, our son’s insulin needs drop every spring, and then gradually rise again, even though his activity level is consistent. | Has the season changed recently? (From winter to spring; from spring to the heat of summer, etc.) At these times, activity levels change, insulin may need to be stored differently to remain effective, and there seems to be some effect that is independent of activity and insulin. For reasons that we can’t explain, our son’s insulin needs drop every spring, and then gradually rise again, even though his activity level is consistent. |
| Has a regular physical activity ended recently? (Gym class switched from Track to Yoga, hockey or soccer season ended) A drop in activity may require a change in insulin dosing . | Has a regular physical activity been introduced recently? (Gym class switched from Yoga to Track, hockey or soccer season started.) An increase in activity may require a change in insulin dosing . |
| NO IDEA WHAT CAUSED the Highs/Lows??? | |
| High Blood Sugar | Low Blood Sugar |
| A pattern of high BG or 50% or more above target may require an increase in the insulin dose (including basal insulin, insulin for food, insulin to correct high BG). Find out more: Adjusting Insulin when using N/NPH Adjusting Insulin when using Multiple Daily Injections (MDI) Adjusting Insulin when using an Insulin Pump | Two lows in a row at the same time of day or more than 3 lows per week may require a decrease in the insulin dose (including basal insulin, insulin for food, insulin to correct high BG). Find out more: Adjusting Insulin when using N/NPH Adjusting Insulin when using Multiple Daily Injections (MDI) Adjusting Insulin when using an Insulin Pump |
Still stuck? Please consult with your child’s diabetes health care team for guidance.
The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.
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