What is Sliding Scale Insulin Therapy?


Sliding scale insulin therapy has been around since the 1930s. It continues to work today for many people with diabetes, but that doesn’t mean it’s without its challenges. 

In this article, we dive into the pros and cons of sliding scale insulin therapy, give an example of a sliding scale chart, provide tips for talking to your doctor about your insulin management needs and explain how different diabetes management tools may help you be successful with sliding scale insulin therapy.

What is sliding scale insulin therapy?

Sliding scale insulin therapy refers to a diabetes management method where someone with diabetes determines their fast-acting insulin dosage needs based on food intake and their current blood sugar levels. Basal (slow-acting) insulin intake is also a part of sliding scale insulin therapy but tends to be more fixed than bolus (fast-acting) insulin intake. 

Basal insulin injections may be taken once or twice per day, typically first thing in the morning or before bedtime. Basal adjustments are usually made with your doctor during a routine checkup, whereas bolus decisions are made daily by people with diabetes. (For example, you may bolus less for a plate of broccoli than an apple.) By working with your doctor, you can find the best insulin sliding scale formula for your body. 

When on sliding scale insulin therapy, doctors typically recommend taking fast-acting insulin 15 to 30 minutes before eating (if your blood sugar levels are within or slightly higher than your goal range). You should wait to take insulin if you are experiencing a low blood sugar level—always ensure low blood sugar levels are stabilized first. Depending on the type of insulin you take and how your body reacts, your doctor may have slightly varied recommendations about bolusing. Boluses are taken before eating or are used to correct a high blood sugar that may or may not coincide with food. 

Your doctor may equip you with a sliding scale chart (demonstrated below) to help make remembering your insulin dosing needs easier.

How does sliding scale insulin therapy work?

Blood sugar levels under sliding scale insulin therapy management can be measured using a continuous glucose monitor (CGM) or blood glucose meter (BGM). Depending on your insulin intake method, whether you use an insulin pump, inhaled insulin, multiple daily injections or a combination of these, sliding scale insulin therapy can look different for everyone!

Sliding scale insulin therapy + high blood sugar levels

Suppose your goal range is between 3.9 to 8.325 mmol/l70 to 150 mg/dL. Let’s say you’ve determined with your doctor that if your blood sugar level is within 49 to 50 points above your goal range, then you should take one additional unit of insulin. Therefore, if your blood sugar level is 10.2675 mmol/l185 mg/dL (35 points above your range) you will take one unit of insulin to correct your high blood sugar because it falls within that high range.

Adjusting your sliding scale for eating

If you are also eating at the time of your high blood sugar, you will need to calculate your insulin slightly differently. If you take one unit of insulin for every 12g of carbohydrate and your meal is worth 104g, you will divide 104 by 12 to get 8.67 and add one unit to account for your high blood sugar to get an exact total of 9.67 units. You’d likely adjust to 9.5 units of insulin in this case as it’s closer than rounding up or down to whole numbers (9 or 10 units).

A half unit measurement is closer in this scenario than rounding your insulin dose up or down, but you should talk to your doctor if this is a concern or you are more likely to run high or low. You can decide together whether you’d prefer to round up or down if half units just aren’t possible. If you use multiple daily injections (MDI), you may not be able to use half units at all because not all insulin pens and syringes include them.

Things get even trickier when you consider the timing of food digestion. For example, if you frontload your insulin with the full 9.5 units in this scenario and are eating thick-crust pizza, you may experience a sudden drop in your blood sugar levels first and then a high blood sugar reading two to three hours later. This happens because dense carbohydrates can take longer to digest. (High-fat foods also lead to slow digestion of carbs, and pizza is typically high fat.) So, if you frontload your insulin, your body’s carb intake won’t sync up effectively with your insulin.

This is why it’s critical to pay attention to how your body reacts to different foods. When you pick up on different patterns, you can better anticipate your sliding scale insulin therapy needs. Then, eating delicious foods like pizza should get easier! 

Your sliding scale chart may look like this:

Sliding scales are adjusted depending on your body’s unique sensitivity to insulin. Your sliding scale insulin therapy needs may evolve with age, hormone changes, weight fluctuations, lifestyle changes, stress, etc.

If you follow a sliding scale insulin therapy plan as described above, here is an example of what your chart may look like if you have moderate insulin sensitivity:

BG mg/dL | BG mmol/l Moderate Insulin Sensitivity (U;units)
70 to 150 mg/dL | 3.9 to 8.325 mmol/l 0U
151 to 199 mg/dL | 8.3805 to 11.0445 mmol/l  1U
200 to 249 mg/dL | 11.1 to 13.8195 mmol/l 2U
250 to 299 mg/dL | 13.875 to 16.5945 mmol/l 3U
300 to 349 mg/dL | 16.65 to 19.3695 mmol/l 4U
350 to 399 mg/dL | 19.425 to 22.1445 mmol/l 5U

Editor’s note: Though insulin sliding scale chart examples on the internet like this (above) are helpful, do not follow them without consulting with your doctor first.

Are there any disadvantages to sliding scale insulin therapy?

Sliding scale insulin therapy has become more controversial recently because it does not always account for past insulin dosing. This heightens the value of continuous glucose monitors (CGM) for some people with diabetes, as they can show blood sugar levels trends as rising or falling versus getting a singular reading from a blood glucose meter (BGM) that gives no insights into these trends. 

Let’s put it into perspective: Suppose you took two units one hour ago but are still high when you’d like to eat and then correct for that high while also taking insulin for your meal. You could experience a sudden drop in low blood sugar if the initial two doses haven’t hit yet. 

Depending on your insulin sensitivity or resistance, you may find that it takes anywhere from 60 to 90 minutes to sink in. 

Diabetes tech on a sliding scale

Insulin pumps and CGMs may help you make more informed decisions on a sliding scale. But—just because they’re advanced technology doesn’t mean they’re always right for you! Everyone has different diabetes management preferences and needs—that’s okay. It’s a privilege to have options.

Insulin dosage history reminders are typically integrated into most insulin pumps, which can prevent you from overdosing on a sliding scale. Some recent advancements in insulin pens (if you prefer multiple daily injections to pumps) can also help, like smart pen caps that (like insulin pumps) can remind you when you last took insulin.

It’s easy to forget past doses as diabetes management becomes so habitual! As the years of diabetes management go by, you may start to second-guess whether you just took two units five minutes ago or one hour ago. It’s important not to confuse timeframes because they can lead to rollercoaster blood sugar levels over time or even more severe consequences. 

Who is sliding scale insulin therapy for?

People with type 1 and type 2 diabetes may use sliding scale insulin therapy. You may also use alternative insulin management methods, like fixed scale insulin therapy where you take a fixed amount of insulin before every meal. This insulin therapy style requires you to be very routine in the number of carbohydrates you consume before administering each dose. 

If you are on fixed scale insulin therapy, you may take five units before breakfast, six units at lunch and four units at suppertime every day, regardless of your blood sugar levels. Changes in fixed scale insulin therapy are typically only made with your doctor during routine checkups or under a doctor’s official advisory (via phone or healthcare portal message, etc.).

Your doctor will help you determine what insulin therapy method is best for you. Personalization is key! Diabetes management shouldn’t be a one-size-fits-all approach because diabetes affects everyone differently. Consider all of your options and tools with your doctor to ensure you select a successful diabetes management plan for you!

Educational content related to type 2 diabetes is made possible with support from Lilly Diabetes. Beyond Type 2 maintains full editorial control of all content published on our platforms.

WRITTEN BY Julia Flaherty, POSTED 03/18/22, UPDATED 10/10/22

Julia Flaherty is a published children’s book author, writer and editor, award-winning digital marketer, content creator and type 1 diabetes advocate. Find Julia’s first book, “Rosie Becomes a Warrior.” Julia finds therapy in building connections within the diabetes community. Being able to contribute to its progress brings her joy. She loves connecting with the diabetes communities, being creative and storytelling. You will find Julia hiking, traveling, working on her next book, or diving into a new art project in her free time. Connect with Julia on LinkedIn or Twitter.