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How-To: Basal Test

Updated: Nov 17, 2022

Living with Type 1 Diabetes means that every day is a science experiment. But unlike science experiments, there's no locking in the findings and calling it a day. Everyday we are figuring out how to correctly bolus for a bagel, or what amount of carbohydrates to eat before working out. Sometimes it works the same way twice, sometimes it doesn't.

As our bodies change, the weather changes, everything changes, so do our insulin needs and then a whole other self-science experiment is begun. One of these science experiments is a basal test. This post will teach you what a basal test is by first defining the two types of insulin we use to stay alive, and how to carry out a basal test to better you and your diabetes care.


There are two different forms of insulin that Type 1 Diabetics need day-to-day: bolus and basal. Bolus is the short-acting, burst of insulin that is given via injection or pump every time we eat carbohydrates so that our Blood Glucose (BG) levels don’t go high. But the short-acting insulin has a life of about 4 hours (depending) and our bodies need a constant supply of insulin throughout the day to function properly. So this is where basal comes into play. The basal insulin is the long-lasting insulin that works to keep our BG at homeostasis when we’re not eating carbs, or doing anything that could impact our BG levels.

On an insulin pump, like I wore for 15 years, these basal rates are set for different times of the day; they are higher during the day when we’re more active and lower at night while we’re stagnant. But this all depends on the diabetic. I used to have a separate basal rate for the first 3 hours of the morning! This insulin is the same insulin we use to bolus when using the pump, but the pump is responsible for slowly dripping the insulin into the body throughout the day.

When diabetics are using Multiple Daily Injections (MDI) like I am now, we take a completely different type of insulin that is made to be long-lasting, meaning it can live for almost 48 hours in the body. I split my long-lasting insulin 60/40 so that there is no tail end to this insulin’s time in my body and I avoid a gap where I have no long-lasting, and inevitably feel very ill.

So what’s a basal test?

Life as a diabetic wouldn’t be so bad if there was a universal users manual that every person diagnosed with a broken pancreas could read, memorize and institute in their life. But this mythical book does not exist, so it’s all about figuring it out for your own. Every diabetic is different and each requires a completely different insulin dosage. Even if they figure out the correct dosage, a change in routine or a growth spurt can take them right back to the drawing board. We figure it out (for the time being) with a basal test.

By eliminating any variables that could fluctuate BG levels, a clearer picture can be drawn of how the basal insulin (whether it be pump, or MDI) is acting in the body. Is it too much? Too little? The best way to figure it out is by starting at your target BG and not eating any carbohydrates or exercising then monitoring the Blood Glucose levels every hour to see what happens.

But what could happen?

Well if the basal is too much, BG levels will start to drop. The idea is by reading this data, the diabetic and their health care team can pin-point where the basal insulin needs to be adjusted. Similarly, if the basal is too little, BG levels will trend upwards and the dosage needs to be increased.

If the basal insulin is incorrect and too much or too little, meal and correction boluses can be difficult. It’s like building a house on a bunch of spiky rocks!

How do I carry-out a basal test?

I always procrastinate these basal tests until I feel so guilty for disappointing my doctors that I finally give in. I just don’t like the idea of not being able to eat what I want, like what if I’m craving a muffin all of a sudden and you’re telling me I can’t eat it?! But conducting a test like this really isn’t so bad. When I was first diagnosed, I was taught that I had to wake up with a steady and in-range Blood Glucose reading and then just eat carb-free until something happened. I was usually very hungry, and tired of pricking my tiny little fingers every hour.

A great way to avoid starvation and tiring out from finger pricks is to do the basal test in sections. One day, try the morning and another day, start around 12pm and go until 6pm. This kind of test does not have to be a continuous 24 hours.

  1. Start with an in-range Blood Glucose level (between 100mg/dL and 150mg/dL) and make sure to stop basal test when out of range (below 70mg/dL or over 250mg/dL)

  2. Avoid exercising or any kind of movement that could raise your heart rate and then change your BG levels.

  3. Zero Carbs! Have a low fat/protein meal before starting the fast as those macronutrients could slow down digestion (which is usually great for sustainable energy but this could lead to an impact on BG levels later on in the test).

  4. Make sure you’re feeling good! If you’re fighting an illness (not diabetes, I mean more like the common cold or flu) then this could impact your sugars and the basal test will lose all value.

  5. Drink water but no caffeine (sorry, coffee lovers!) or alcohol!

  6. Keep track of everything! For example, when I was doing a basal test, I sliced my finger pretty badly on a knife and I was thinking this stress on my body could fluctuate my sugars so I made sure to take note of it!

Always, always consult your doctor before doing a basal test because although I have been living with Type 1 Diabetes and visiting doctors every three months for 17 years, I am not a medical professional. Doctors will also be the ones to decide if this is necessary for you, and will help you target a specific time of day to engage in the basal test.

xoxo Ciara

#basal #basaltesting #basaltest

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