Everyday with type 1 diabetes is a science experiment. Sometimes what we do one day doesn’t work the next. Learning how to test basal rates whether you’re on MDI or an insulin pump is one of those science experiments you’ll want to know how to do. Because if your basal insulin isn’t adjusted properly, nothing else works right.
How to Test Basal Rates for MDI and Pump Users
You might associate basal rate testing with insulin pumps. Which makes sense because “basal rate” is a phrase that is typically associated with insulin pumps. But your “basal” is just your background (or long acting) insulin.
Pumps offer a lot more flexibility when it comes to adjusting your basal rate, but it’s still important to test your basal rates if you’re on MDI (multiple daily injections), because as our bodies change, the weather changes, or ANYTHING changes, so do our insulin needs.
Why does a pump offer more basal flexibility?
An insulin pump automatically delivers basal insulin every 5 minutes. And depending on the pump, you can set 24-48 different rates throughout the day; giving yourself more during the day (your active hours) and less at night (during your stagnant hours). I personally don’t know of anyone who has that many rates set up on their pump, most people I know (myself include) have between 2-5, but the flexibility is there.
MDI basal, on the other hand, is typically administered once or twice a day with pretty drastic tail. Most people that I know who are on MDI (and myself when I was on MDI) choose to inject their basal twice a day to avoid the tail gap.
Before You Test Basal Rates, Know This!
Basal rate adjustments are usually very small. Like 10-20% small. For example, if I knew I needed to increase my basal and it was currently set at 1 unit per hour, I would only increase it to 1.15 unit per hour (a 15% increase) and see how that goes for a day or two. You might think that it’s not enough to make a difference, but usually it is.
MDI can’t get as precise as a pump, so you might have to round up a bit or down a bit. For example, If you’re giving yourself 8 units of long acting and know that you need more, instead of giving yourself 10% more (which would be 0.8 units more – impossible on MDI) you might choose to round down to a half unit (meaning you’d be taking 8.5) or round up to a whole unit (meaning you’d be taking 9 units).
It’s typical for basal to make up 50% (with a variety of 40-60%) of your total daily insulin; meaning basal + bolus (aka long acting + short acting). If you eat low carb you’ll have a higher percent as basal. And if you eat high carb, you’ll have a lower percent as basal.
Most women will become insulin resistant for the two weeks after ovulation (Luteal phase). You may need a general increase of 20-40% more basal insulin during this phase. Read more about this phenomenon HERE.
How to Test Basal Rates
- Give your normal basal for the day.
- Block out your day into 4 sections. morning, afternoon, evening, and overnight.
- Choose a section to test. Only test 1-2 sections per day.
- Start test with a stable BG between 70-130.
- For the entire duration of the section don’t eat, work out, give insulin, or drink caffeine or alcohol.
- Check in on BG hourly (CGM or finger prick).
- If blood sugar rises or falls more than 50 points from where you started, that means your basal is off and needs adjusting.
Here’s a Breakdown of How to Test Basal with More Details
- Give your normal basal for the day.
- Block out your day into 4 sections. morning, afternoon, evening, and overnight. While these hours may vary for you depending on what time you go to bed, they’re a good guideline for someone who wakes at 7am and goes to bed at 10pm.
• Morning (5hrs): 6:30am-11:30am
• Afternoon (5hrs)11:30am-4:30pm
• Evening (5hrs) 4:30pm-9:30pm
• Overnight (9hrs) 9:30pm – 6:30am
- Choose a section to test. Only test 1-2 sections per day. Doing everything at once might sound practical, but often leads to inaccurate results. Your body goes into starvation mode and builds ketones that weaken the effects of insulin.
- Start test with blood sugar between 70-130mg/dL and no insulin on board (other than basal). If your blood sugar isn’t in range, choose another time section to test.
- For the entire duration of the section don’t eat, abstain from working out, and don’t drink caffeine or alcohol.
- Check in on BG hourly. For the overnight portion, CGM users can get a peaceful night sleep, but for MDI users, if you can test right before bed, once or twice between 12-4am, then again right when you wake up, you should have pretty good indicator of what your blood sugar is doing overnight.
- If blood sugar rises or falls more than 50 points from where you started, that means your basal is off and needs adjusting. Depending on how comfortable you feel with the rise or fall you can wait an hour or so to see if it keeps climbing or dropping. This will give you a better idea of how much adjusting you need to do.
Making Adjustments to your Basal Rates
Here is a general rule of thumb for adjustments:
- If your blood sugar rises 50mg/dL: increase basal by 10%.
- If your blood sugar rises 100mg/dL: increase basal by 20%
- If your blood sugar drops 50mg/dL: decrease basal by 10%
- If your blood sugar drops 100mg/dL: decrease basal by 20%
Once you make adjustments to your basal rates you’ll have to retest that section again to see if you’ve fixed what you intended to fix.
For Those on MDI
While you can’t change what your basal rate is every hour, like you can on a pump, you can change the timing of your injection(s) to better meet your insulin needs.
Most long acting insulin has a lifespan of 24 hours, with a peak at 6 hours. Knowing this you can time your injection so that your peak happens at the time when you need the most insulin.
Some people metabolize insulin faster than others and their long acting insulin might only have a 12 hour life span with a peak of 3 hours. Which is why some people choose to split their dose and inject every 12 hours.
Printable Worksheet to Test Basal Rates
If you work better with pen & paper, or just love the look of handwriting on a piece of paper (guilty), I’ve made a printable worksheet to test basal rates.
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