From Sliding Scale to Carb Counting: How Insulin Dosing Has Evolved

Many people with type 1 diabetes (T1D) often hear the term “sliding scale insulin” (SSI) when they are diagnosed or early in their diabetes journey. The phrase “carb ratios” usually comes up from healthcare providers who specialize in diabetes care, like endocrinologists or certified diabetes care and education specialists (CDCES).

Although these terms might seem like very different ways to manage diabetes, they actually show two different ways of thinking about insulin doses. 

These terms are not just for healthcare providers—people with diabetes (PWD) need to understand them too, especially when taking care of their health at home. SSI and carb ratios (ICR) are for people with type 1 and some with type 2 diabetes who take insulin.

This guide explains the differences between SSI and ICR in simple terms for people with diabetes.

A simple explanation of 2 insulin dosing strategies

Here’s a simple way to understand the difference between ICR and SSI: 

• One approach is reactive—it asks you to respond to high blood sugar. That’s SSI.
• The other approach is proactive—it asks you to match your food to your insulin needs before your blood sugar levels rise. That’s ICR.

While a simple explanation helps for general understanding, a deeper look provides even more useful information for daily life with diabetes.

What is sliding scale insulin therapy?

Sliding scale insulin therapy depends on your current blood sugar level. If you are on SSI, you will use a chart that shows your insulin dose based on your blood sugar range.

For example, that chart might show you instructions like:

• 150-200 mg/dL: take a small dose of insulin
• 200-250 mg/dL: take a larger dose of insulin
• 250 mg/dL+: take an even larger dose of insulin

For example, a small dose could be one unit, a large dose might be two units and an extra-large dose could be three units. Those doses are determined by your healthcare provider.

Sliding scale insulin therapy doesn’t take into account how many carbohydrates you eat or how sensitive your body is to insulin. It is a reactive approach, meaning the amount of insulin you take is based on blood sugar levels rather than predicting them in advance. This method is often used in hospitals because it’s simple, and a few healthcare providers  still use it in their clinics.

When you can proactively anticipate blood sugar changes rather than react to them afterward, it means meeting blood sugar goals more consistently. Major diabetes guidelines recommend using additional strategies beyond short-term insulin adjustments to manage T1D.

What are insulin-to-carb ratios?

Insulin-to-carb ratios are a modern approach to dosing your insulin at mealtime. Insulin-to-carb ratios are used to calculate how much insulin you need for the carbohydrates you’re consuming.

For example:

• 1 unit for every 15 grams of carbohydrates

If you were dosing 1 unit for every 15 grams of carbs, that might look like:

• Giving a dose of three units of insulin for 45 grams of carbohydrates
• Giving a dose of five units of insulin for 75 grams of carbohydrates

You get the picture! Insulin-to-carb ratios allow for more freedom and flexibility in  your food choices, matching your insulin needs to your food intake. Insulin-to-carb ratios are always individualized. No two people manage T1D the same way, so diabetes management strategies will always differ slightly.

Your healthcare provider (HCP) will help you determine what your insulin to carb ratio should be. ICRs change over time as your body changes too, so if you notice patterns of high or low blood sugar after meals—let your HCP know. 

Insulin-to-carb ratios may vary based on:

• The time of day
• How sensitive your body is to insulin
• Hormones

How has sliding scale insulin therapy logic evolved?

The logic of sliding scale insulin therapy hasn’t completely disappeared—it’s just evolved. The SSI has been replaced with something called a “correction factor.” Correction doses are used to correct high blood sugar. The recommended blood sugar target range for an adult with any type of diabetes is approximately 3.885 to 9.99 mmol/L (70 to 180 mg/dL). If your current blood sugar level is above this range, you can use the correction factor to give additional insulin to help lower you back into target range..

Correction factors may advise you to:

• Give one unit for every 40 points you are above your target blood sugar range
• Give one unit for every 50 points you are above your target blood sugar range
• And so on

Correction factors are based on your individual ISF. They are not taken from one-size-fits-all models of diabetes care. It’s important that they are tailored just for you.

This is the modern way of understanding SSI. That’s why you’ll still see it on your charts during your regular checkups and why your healthcare team asks about it at every visit.

Pairing ICR with Correction Dose

Pairing a ICR pre meal calculated dose with a correction factor for high blood sugars has become a common practice for people with diabetes. 

Practically, that may look like this:

• Let’s say your HCP determines your ICR is 1:10 and your correction factor is 1 unit for every 25 points your blood sugar is above 150mg/dL. You’re about to eat 50 grams of carbs and your blood sugar is 200 mg/dL before your meal, you would dose 5 units of insulin for the carbs, plus an additional 2 units of insulin to correct your high blood sugar, that’s a total combined dose of 7 units. 

The role of sliding scale insulin therapy in the hospital setting

Some hospitals still use sliding-scale protocols because they are easy for rotating staff to follow. When someone with diabetes is in the hospital, their food intake might be unpredictable, which makes managing insulin more challenging. Sliding scale insulin therapy is also helpful if a person with diabetes is sick, can’t eat well or has trouble predicting their blood sugar levels when illness raises their blood sugar.

Sliding scale insulin therapy should never replace basal (background/long-acting) insulin for people with T1D. That’s necessary at all times!

Predictive vs. reactive insulin therapy

To recap, SSI reacts to high blood sugar and ICR anticipates it. It matches your insulin doses to real-life factors, including your carbohydrate intake and your current blood sugar level. 

Modern insulin dosing strategies try to mimic how the pancreas actually works in a person without diabetes. It considers:

• Meal coverage
• Background insulin
• Correction doses, when needed
• How much insulin you have on board (how much insulin is in your system)

Sliding scale insulin therapy alone might not work for many people with T1D. But when combined with ICR, it becomes a strong and helpful tool. If you’re unsure about your correction factors or how to dose insulin for meals, always ask your healthcare team. They can help you understand and guide you. Their support is available to make living with diabetes easier. 

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