Checking & Adjusting Basal Rates PUMP

Adjusting Insulin (Pump): testing & tweaking basal rates

Basal insulin is the background insulin which, if set properly, keeps blood glucose steady in the absence of food and exercise. But how can you tell whether the current basal rates programmed into your child's insulin pump are working well or not? Here we look at how to assess the current pump basal rates, including the conditions for effective basal testing. Then we outline the process of adjusting them if needed, suggest how much to adjust settings by, and give some practical tips from our own experience with basal testing with our young T1D son.

Before Reading This Article...

If you have not done so already, we recommend that you read the following pages on insulin adjustment for pumps:

A Basal-Bolus Approach to Insulin Pump Therapy

How Insulin Action Impacts Blood Glucose in an Insulin Pump Program

Insulin Adjustment for Pumps: an Overview

Pump Record Review

Basal Insulin

Basal insulin is the background insulin which, if set properly, keeps blood glucose steady in the absence of food and exercise. A healthy pancreas secretes a small amount of basal insulin into the bloodstream every few minutes, to match the small amounts of glucose released by the liver on a continuous basis, so that glucose can be used by the body’s cells for basic energy needs. For a person with type 1 diabetes using an insulin pump, basal insulin is delivered as rapid-acting insulin (such as, here in Canada: Humalog®, Novorapid®, or Apidra®) given every few minutes in tiny doses.

Basal insulin needs vary from person to person, and across the lifespan. Adults and adolescents typically need more basal insulin in the early morning hours to deal with the release of hormones involved in waking (known as the Dawn Phenomenon). Children often need more basal insulin in the late evening hours to deal with the release of growth hormones a few hours after they fall asleep.

Initial Basal Doses

If your child is about to begin using an insulin pump, the basal rates that will initially be programmed into the pump should be provided by your child’s doctor and diabetes health care team, based on the basal dose of long- or intermediate-acting injected insulin before pump start, and/or your child’s age, size, growth stage, and activity level. As your child grows, changes will need to be made to these programmed basal rates. Periodically, you may want to test/verify how well your child’s existing basal rates are meeting her current need for insulin. You could then use the results as a basis of discussion with your child’s diabetes health care provider.

Assessing Current Basal Rates

Eleanor Roosevelt might as well have been predicting the use of insulin pumps when she said, “With freedom comes responsibility.” The use of a pump means we are not tied to a single basal rate all day; it means we don’t have to cope with the midday highs just to avoid the overnight lows; it means we can program many different basal rates, in different time periods throughout the day and night. But that freedom and flexibility will not improve blood glucose control if we do not take on the responsibility of assessing and fine-tuning the programmed rates (including basal rates) to reflect a child’s actual insulin needs at different times of the day.

Tip from the Trenches

This fine-tuning process may seem daunting. My own son was using a pump for well over a year (with many BG swings!) before we finally bit the bullet and empirically tested the basal rates which we had programmed into the pump based on estimates and then fiddled with based on hunches. No surprise: when we actually tested these basal rates, we ended up making changes to almost all of them. And as our son grows and his metabolic needs change, it would be wise for us to repeat this testing process to determine the optimal basal rates for him on an ongoing basis. ~Michelle

Since the goal of basal insulin is to keep blood glucose steady in the absence of food, exercise and bolus insulin, you can assess how well the current programmed basal rates are meeting that goal by, for a given time period, eliminating the effects of food, physical activity, and bolus insulin on blood glucose, so that the effects of basal insulin alone can be assessed.

There are 2 different approaches to checking the current basal rates:

  • Method 1:

Take advantage of occasions when a snack or meal is naturally delayed or skipped. If on a given day, he is not hungry at lunch time, sleeps in past his usual breakfast time, or supper is served later than usual when an activity interrupts your family schedule, check blood glucose and use the data to assess basal rates. Did blood glucose spike in the absence of food, exercise and bolus insulin? Did it drop significantly? If blood glucose varied by more than 2.0 mmol/L in the absence of food, exercise and bolus insulin, you may want to consider a change to the existing basal rates.

  • Method 2:

Conduct a more formal fasting basal test, which involves avoiding (for a minimum of 5 hours, up to 8 hours) any food/drink which may raise blood glucose. For a fasting basal test, the following chart gives an example of how you may split  the day into four time periods (you would then choose one time period in which to conduct a fasting basal test):


 Testing Period 
No food, exercise, bolus insulin after: 

Resume usual food, exercise, bolus insulin at: 
 Overnight   10pm – 8am    6 pm
(skip bedtime snack)
8 am
 Morning  8am – 12pm 4 am
(skip breakfast)
12 pm
 Afternoon  12 – 5pm 8 am
(skip lunch)
5 pm
 Evening   5 – 10pm 1 pm
(skip supper, late or no bedtime snack)
10 pm

Conditions for Basal Testing (Methods 1 & 2)

In order to get valid results from a basal test (whether using Method 1 or Method 2) it’s preferable for your child to get as close as possible to the following circumstances:

  • not eat/drink during the test period and for 4 hours before the test period begins. This means that only water and diet drinks (0 calorie, 0 carb) are allowed.

If you are using Method 1, and your child finished lunch at 1:00pm, you can assess the 5:00-7:00 time period by delaying supper until 7:00pm providing only 0 calorie, 0 carb food and drink from 1-7 pm.

If you are using Method 2, and your child finished lunch at 1:00pm, you can assess the 5:00-9:00 time period by providing only 0 calorie, 0 carb food and drink from 1-9 pm.

Sound impossible for your child? You may want to give it a try before dismissing the idea.  I was amazed at what some home-made popsicles and snowcones, in the presence of a plethora of fun distractions, could do to help the time pass for my 4-year-old son.  ~Michelle

  • eat a healthy meal/snack before the test period, avoiding fatty foods and restaurant/takeout food. Ensure the carb-content of the meal is known.
  • avoid caffeine during the test.
  • consume only water and diet drinks (0 calorie, 0 carb) during the pre-test and test period.
  • not bolus for 4 hours before the test.
  • not exercise during the test period. (Light to moderate physical activity is okay, if your child usually does so at that time of day.)
  • not have had any lows in the last 12 hours.
  • not be sick. (If you suspect that she is, postpone the test for another day.)
  • not be at the beginning of or just prior to her menstrual cycle.
  • not disconnect or suspend the pump during the pre-test or during the testing period.

The Basal Test Process

  • Check your child’s blood glucose at the start of the test period (4 hours after they finished eating).
    • If blood glucose is 4.0 mmol/L or less, end the test and give the usual low treatment. You’ll need to wait until another time to test basal rates.
    • If blood glucose is 14.0 mmol/L or greater, end the test and give the usual correction dose of insulin. You’ll need to wait until another time to test basal rates.
    • If blood glucose is between 4.1 and 13.9, you may choose to continue the test as follows:
  • Check blood glucose every 1-2 hours (at least once for the overnight phase, or as frequently as every 3 hours, if desired).

We did a finger poke every half hour during the daytime basal testing periods. In hindsight, this was overkill; I figured if we were going to make the effort, we were going to make it worth it, but in reality we didn’t lose any information testing every hour.    –Michelle

  • A Continuous Glucose Monitor (CGM) may be used in addition to fingerpokes. This may provide additional information about blood glucose trends and the rate of change of blood glucose during the test. It would also allow for fewer fingerpokes during the basal test.


Why Check Blood Glucose in the Middle of the Night?

If we checked blood glucose at bedtime and at wakeup only, and found more than a 2.0 mmol/L rise, there are at least a few possibilities in terms of what happened overnight:

Waltzing The Dragon Inc

A. blood glucose may have risen steadily;

B. blood glucose may have stayed steady in the first part of the night, followed by a sharp increase in the latter part of the night; or

C. blood glucose may have dropped in the first part of the night and then rose sharply as a result of the preceding low blood glucose.

This last scenario is referred to as a “low rebound” (or, the Simogyi Effect): as a result of a low, the liver releases stored glucose (glycogen), resulting in high blood glucose later. In order to rule out an undetected low, it is essential to check your child’s blood glucose at least once midway through your child’s sleep time.

How we deal with the overnight rise in blood glucose depends on which of the above scenarios actually occurred:

  • If blood glucose rose steadily overnight as in A: it makes sense to increase the basal rates throughout the night.
  • If blood glucose remained steady for part of the night and then increased towards morning as in B: you may choose to increase the basal rate for the second half of the night.
  • If blood glucose dropped and then rose as a result, as in C: then a decrease in the basal rate for the first half of the night may actually result in lower waking blood glucose readings.

If you would like assistance with sorting out the possibilities, please consult your child’s diabetes health care team.

(If you’re a Type A personality like I am, during a basal test you may choose to do 2 checks in the middle of the night: 12 am and 3 am, for example.  ~Michelle)

Adjusting Basal Rates Based on the Test Results

If the results of the basal test show a significant rise or fall in the blood glucose readings (2.0 mmol/L or more in either direction), consider adjusting the basal doses that are affecting that time period, by changing the rate programmed for 1 – 2 hours* before the rise or fall occurred. For example, if blood glucose begins to drop (or rise) at 3 pm, the 1pm or 2pm basal rate may need to be adjusted.

*Some experts recommend 1 hour for children and 2 hours for adults. Others recommend making smaller changes up to 4 hours before the rise or fall in blood glucose. You will need to experiment with timing of rate changes to meet your child’s individual needs.

  • If blood glucose stayed steady over the test period (within 2.0 mmol/L), no changes to the basal rates seem to be needed at this time.

For example, the blood glucose reading at 12 pm (4-hours post-meal) was 8.9 and the subsequent hourly blood glucose readings were:

1 pm:  8.2
2 pm:  7.8
3 pm:  7.7
4 pm:  7.9
5 pm:  8.4

Blood glucose dropped from 8.9 to 7.7 at the lowest point, a drop of only 1.2 mmol/L. This verifies the current basal rates for 11 am to 4 pm. At this point, there doesn’t seem to be an obvious need for changes to those basal rates.

  • If blood glucose dropped more than 2.0 mmol/L during the test period, consider a decrease in the basal insulin affecting blood glucose during that time period.

For example, the blood glucose reading at 12 pm (4-hours post-meal) was 8.9 and the subsequent hourly blood glucose readings were:

1 pm: 8.2
2 pm: 7.8
3 pm: 7.5
4 pm: 7.1
5 pm: 6.2

Blood glucose dropped from 8.9 to 6.2, a drop of 2.7 mmol/L. It did so in the 12 to 5 pm time period, so consider adjusting the basal rate from 11 am to 4 pm.

  • If blood glucose rose more than 2.0 mmol/L during the test period, consider an increase in the basal insulin affecting blood glucose during that time period.

For example, the blood glucose reading at 12 pm (4-hours post-meal) was 8.9 and the subsequent hourly blood glucose readings were:

1 pm: 8.6
2 pm: 9.1
3 pm: 9.9
4 pm: 11.1
5 pm: 11.7

Blood glucose held steady from 12 – 2 pm, but rose in the 2-5 pm time period. It rose from 9.1 to 11.7, a rise of 2.6 mmol/L. Since the rise occurred in the 2 to 5 pm time period, consider adjusting the basal rate from 1 pm to 4 pm.

By How Much Should I Adjust?

Moderate BG Change

For a moderate rise or fall in blood glucose, if your child is on relatively small amounts of basal insulin, you may choose to adjust the basal rate by only 0.05U/hour or less. If your child is on larger amounts of insulin, you may choose to make adjustments of 0.1U/hour or more.

Tip from the Trenches

On our son's first pump (Animas) basal rates could be adjusted in increments of 0.025U – we usually made adjustments of 2 "jumps” (or 0.050U) when adjusting our 4 year old son’s basal rates. If the affect of this change was too large, we would then back it up “1 jump”.   ~Michelle

Large BG Change

For a dramatic rise or fall in blood glucose, you may choose to make adjustments in increments of 0.10U/hour (or more if your child is on large amounts on insulin).

If you are adjusting for a basal dose that is much too high, resulting in lows which come on very quickly during basal testing, it is wise to make significant adjustments in the basal rate. You can always increase the basal rate in small increments after jumping down to a safe basal level.

Consult your child’s diabetes health care team for guidance on how much to adjust the basal rates. You may find that the Diabetes Nurse Educator, Certified Diabetes Educator, or Pump Trainer on your child’s health care team will have the most experience in this area.

Tip from the Trenches

You may also choose to incorporate an independent CDE within your child’s diabetes health care team to facilitate this process. We were very pleased with the support offered by Gary Scheiner at Integrated Diabetes Services. As part of a CGM rental service, Gary also helped us structure the testing process and analyze the results – we would not have been so successful on our own! ~Michelle

Tips from the Trenches for Basal Testing

  • We bought popsicle molds from Toys R Us and a local loonie store – multiple shapes and sizes to ward off boredom. We then filled them with a variety of colours and flavours of diet drinks and froze them overnight to make home-made popsicles.
  • We also made snow cones by blending ice and diet drinks in the blender.
  • We were amazed at the wide variety of diet drinks available at the grocery store. At Safeway™ and Superstore™, we found all the usual Pepsi and Coke products, including Fresca, Caffeine-free Diet Pepsi/Coke, and Diet Sprite/7-Up. We also found a number of Safeway and PC brand diet sparkling waters, in yummy flavours such as watermelon-strawberry, tangerine-lime, mountain berry, apple-pear and lemon-lime, to name just a few. Also, we found Powerade Zero (must be “Zero” – regular Powerade contains carbs)  in blue (Mixed Berry) and red (Strawberry). We hear there is also a purple (Grape) available.
  • Read the labels to make sure the diet drink is 0 calorie and 0 carb. Some products we found had calories, even though they had no carbs – these will NOT work for basal testing.
  • When buying diet pop, you may want to buy only caffeine-free varieties, as caffeine may raise blood glucose. Although more recent studies have shown that coffee is the only caffeinated drink which raises blood glucose, it used to be thought that any caffeinated drink would have this effect. If you want to be extra cautious, go for caffeine-free pop. (We also didn’t want our young son, who has yet to experience caffeine, to be up all night after nine Pepsi popsicles! So caffeine-free diet Pepsi it was.)
  • For variety, try pop with different flavours and colours (orange pop, red cream soda, etc.) We coloured the clear diet drinks with food colouring or powdered Kool-Aid (WITHOUT the sugar that was recommended on the package!) Just be careful with popsicles coloured with food colouring – as they melt, they will stain the clothing, furniture and carpets that they drip on!
  • If you were planning on adding any new toys, games, books, videos, computer/video games, or smartphone apps to your household, now is the time. We found we only needed a few unfamiliar videos, one as-yet-unread book, and a new board game to help distract our son during the multiple test periods. Consider borrowing these items (from a friend, family member, or the public library) rather than going to the expense of purchasing them. So that we didn’t burn through these supports too quickly, we found it worked best to hold them back at the beginning of the test period and present them only when we encountered a “bump”.
  • Give some thought in advance to the best approach for your child, at the age they are and with the individual personality they possess. In some cases it will be best to be totally upfront with your child: tell her what needs to be done and why it’s important, as well as what the benefits are to her personally (ex. She may have fewer highs, so will perform better on the basketball team. She may have fewer lows so won’t have to deal with that shaky panicky feeling as much. She will get to sleep in on weekends because you will be more confident her blood glucose won’t go low.)
  • Consider your child’s personality and age in deciding when and how much to tell them about the process.
    • At the outset, we didn’t tell our son that he couldn’t eat for 8 hours. Instead, we told him he could have all the popsicles he wanted, in any colour, between now and supper. He was thrilled at the power and control he had over his day.
    • I cannot underscore enough the power we have to “sell this”, especially to younger children. They look to us for clues about how they should feel about things – if we are upbeat and confident, it goes a LONG way to getting “buy in”.
  • After the fast ended, we told our son what he had accomplished, how strong and brave he was, and how proud we were of him. I think this went a long way towards finishing the test the next time, as he knew he could do it – he had already done it before.
  • If you have other children who will not be fasting during the same time period, decide in advance what the rules are around eating: Can they eat in another room? Out of the house? Is it best if they go to a friend or family member’s house during the test period? Do you need to plan the testing for a time when both parents (or a parent and a helper) can be present? I found it challenging on my own to juggle fasting for my son with my 2-year old daughter’s need to eat. It was do-able, but much easier when my husband was home and could bring my daughter into her room for a meal or snack while my son ate popsicles and played Dora Uno with me.
  • Having a meal ready and waiting in the fridge really helps. At the end of the test period, I wanted to be able to feed my son immediately. And he wanted to eat immediately.
  • After one basal test, a ketone test showed that my son had developed starvation ketones as a result of fasting for several hours. As his blood glucose was in the target range, we were not concerned and treated them with food and the usual insulin (no extra insulin). HOWEVER, it is wise to keep in mind the usual guidelines for individuals with diabetes who have ketones (see Ketones and DKA; the section titled “Ketones + Target BG + NO signs of DKA” is relevant for fasting basal testing).
  • Before we started this process, I felt REALLY bad about putting my son through this. What kind of mom doesn’t let her kid eat for eight hours?! So I chose to fast with him, not just because I felt it wasn’t fair to ask him to do something I wasn’t willing to do, but also to calm this guilt. In the process, I learned a few things:
    1. It wasn’t as bad as I thought it would be.
    2. Hour 4 was tough. Then my body kind of got over expecting to be fed. Until the last hour, but by then we were so close, that got us through. In other words, it’s not a full eight hours of torture. 🙂 It is manageable.
    3. Drinking lots helps control the feeling of hunger. (I mean water and diet drinks!)
    4. The information we received from the process was well worth it to us, especially from the first few tests. It is not something I would choose to do all the time, especially if I can get “good enough” information from easier methods. But when things were a confusing mess for us, it really helped us to take a few variables out of the equation.     ~Michelle

Fasting Basal Testing is Not the Only Way

  • This process is OPTIONAL. There are other options for insulin adjustment with a pump (such as Pattern Adjustment). You are the only ones who can decide whether this approach is appropriate for your family at this time: Is there room for improvement in your child’s A1C or is it already at an acceptable level? Are the majority of blood glucose checks already within the target range? Or does your child experience more “swings” from highs to lows than you or your child are comfortable with? How much will basal testing “cost” your family? Are the possible benefits worth the effort? Is there any reason why your child should NOT participate in a fast (such as other medical conditions which may make fasting risky)?

Tip from the Trenches

Although my son, Paul, has never participated in a formal basal testing fast we often test his basal rates by having our meals at later times than usual. If my son says he’s not hungry for a meal, we use that as an opportunity to test. I let his body decide how long to go without food. Sometimes I will just plan a later supper at 7pm to check basals. By using this approach, it has worked out for us to cover all the time slots without a more comprehensive fasting basal test. ~Danielle

The above information was reviewed for content accuracy by clinical staff of the Alberta Children’s Hospital Diabetes Clinic.