Understanding insulin therapy basics

When you have diabetes, managing your insulin is paramount to keeping your blood sugar in check. But whether you’re starting insulin therapy for the first time or refining your regimen, understanding insulin dosing isn’t always easy.  

Getting your insulin regimen right involves the timing of doses, amount you take, the type of insulin and delivery method.

“Sometimes insulin therapy can be a challenge, but learning how insulin affects your blood glucose can help you better manage your diabetes,” says Jill Fabri, RDN, a registered dietitian nutritionist and certified diabetes educator and care specialist at Geisinger. “And with the right plan and support, insulin therapy can be a powerful tool to help you feel your best and protect long-term health.” 

Why insulin therapy?

With Type 1 diabetes, your body stops making insulin and in Type 2, your body doesn’t respond to it properly. This is called insulin resistance. 

Insulin is a hormone produced by the pancreas that helps cells absorb glucose for energy. But if your body doesn’t make enough insulin or becomes insulin resistant, glucose builds up in the bloodstream and leads to high blood sugar levels.

Insulin therapy replaces or supplements your natural insulin with varying types and dosing strategies to keep your blood sugar within target range — and helps prevent serious complications. 

Types of insulin

Insulins differ in how quickly they start working, when they peak and how long they control blood sugar. There are 2 main types of insulin:

Bolus insulin

Bolus insulins are taken before or during meals to manage rises in blood sugar after eating by helping cells absorb glucose. They can also help correct high blood sugar. They start working much faster than long-acting (basal) insulins and can last up to 6 hours.

• Rapid-acting insulin, taken before mealtime, starts to work in about 10 to 15 minutes. It peaks in about 60 to 90 minutes and stays active for about 3 to 5 hours. Ultra-rapid insulin can be injected 15 minutes before or immediately after a meal and also can last 3 to 5 hours.
• Regular or short-acting insulins start to work in about 30 to 60 minutes and can last for up to 6 hours. They peak about 2 to 4 hours after injection and are usually taken 30 minutes before mealtime.

Basal insulin

Basal insulins provide a steady baseline to keep blood sugar stable between meals and while you sleep, and  last much longer than bolus insulins.

• Intermediate-acting insulin begins working in about 1 to 2 hours and peaks between 4 and 10 hours after injection. It works for about 12 to 18 hours.
• Long-acting and ultra-long-acting insulins last much longer, and depending on which type, their actions can last from 12 to 42 hours. 

There are also premixed insulins that include both short-acting (bolus) and long-acting (basal) types.

Insulin therapy to control blood sugar

If you have diabetes, gradually adjusting insulin helps you reach blood sugar targets without frequent highs or lows. But your insulin dosing schedule depends on several factors, including your diabetes type, your blood sugar levels and how much they change throughout the day. 

If you have Type 2 diabetes, insulin therapy may not be part of your treatment plan. It’s only needed when lifestyle changes and other medications don’t control your blood sugar well enough. 

But if you have Type 1 diabetes, you must take insulin every day to stay healthy, usually with multiple injections. This often means a dose of long-acting insulin once or twice a day, along with rapid-acting insulin before each meal to mimic the body’s natural insulin production.

“When using insulin therapy, typically 50 percent of the total daily insulin dose is given as basal, or long-acting insulin, which controls glucose between meals and during sleep,” says Ms. Fabri. “The other 50 percent is given as bolus, to cover meals and correct high blood glucose.” 

Because everyone has different insulin needs, your provider will prescribe an insulin dose regimen for you. You might only need a basal (long-acting) insulin or you may require both basal and bolus (mealtime) insulins.

For example, some people may follow a set dose of mealtime insulin, while others may use a more flexible way of dosing like an insulin-to-carb ratio — a formula used to calculate an insulin dose based on the amount of carbs consumed during mealtime. In addition, a correction scale for dosing also may be used to correct high blood sugars.   

Tailored insulin regimen

Insulin requirements vary from person to person, so insulin therapy should always be tailored to the individual. Setting the right dose depends on insulin sensitivity, or how effectively your body responds to insulin, and:

• Weight
• Hormone levels
• The type of diabetes you have
• Diet and daily eating pattern
• Physical activity
• Stress level
• Illness or other chronic conditions
• Medications you’re taking

Based on these factors, your doctor can determine an insulin regimen that is best suited for you to help keep your blood sugar in target range.

“Keep a record of doses, meals and blood glucose readings to identify patterns, so your provider can better determine how to adjust your insulin doses,” says Ms. Fabri. “And if you’re unsure about an adjustment, schedule a visit with your diabetes specialists.”

Methods to take insulin

Insulin doesn’t work in a pill form. Instead, there are several ways to take it: 

• Syringes or pens: The most common method, insulin injections deliver medicine with a syringe and needle or pen-like device, usually in the abdomen, upper arm or thigh. 
• Insulin pump: An insulin pump gives small, steady amounts of insulin throughout the day through a catheter placed under the skin. It also can give a larger dose of rapid-acting insulin for meals or corrections. 
• Inhaled insulin: Using an inhaler, rapid-acting insulin in breathed in through the mouth, usually at the start of a meal. 

“If you’re using insulin syringes or pens, don’t inject in exactly the same place each time because hard lumps or scar tissue can develop and will affect the absorption of insulin,” says Ms. Fabri. “Instead, rotate injections in fleshy or fatty areas like the abdomen, upper arm, sides of thighs or top of buttocks.”

When to talk to your doctor

If you notice frequent highs or lows, schedule an appointment with your provider. Your endocrinology team can review your glucose data and help adjust your insulin regimen, and tailor your dosing around your diet, activity level and lifestyle to better reach your blood sugar target. 
Seek immediate medical attention if:

You have symptoms of high blood sugar (hyperglycemia), such as:

• Blurred vision
• Frequent urination
• Extreme thirst
• Vomiting
• Seizures
• Loss of consciousness

Or you have symptoms of low blood sugar (hypoglycemia), such as:

• Dizziness
• Headache
• Shakiness
• Sweating
• Fainting or weakness

“Insulin therapy sometimes can be a challenge, but it can be an effective way to manage your blood sugar,” says Ms. Fabri. “Understanding your insulin dosing and knowing the signs of high and low blood sugar can help you safely manage your diabetes. And with time, you can find an insulin routine that fits your needs and help you lead an active, healthy life.”

Next steps: 

Learn what to eat if you have diabetes
Find out how to shop safely with internet pharmacies
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