When you have diabetes, insulin is vital to helping you keep your blood sugar levels in check.
If you have type 1 diabetes, you must inject insulin daily. Those with type 2 diabetes may also require insulin injections to maintain their blood sugar levels.
Not all insulin types are the same. Pharmaceutical manufacturers make long-acting, intermediate-acting, and short-acting insulin options. If you do inject insulin, the best way to start a treatment plan is to contact your doctor.
This article will give a general overview of how to determine how much insulin to administer, but it’s not a replacement for medical advice from a healthcare professional.
In people who do not have diabetes, their bodies release insulin in response to the foods they eat. This is because many foods contain carbohydrates. Some examples include bread, sweets, fruits, and even vegetables.
Your body breaks carbohydrates down into smaller building blocks, like glucose. You need insulin to use this glucose for energy. If your body cannot make or use insulin effectively, you’ll need to inject it to process your food for energy.
Calculating how much insulin to take is usually based on two considerations:
Anticipating a bolus dose is where insulin administration can get tricky. When you give yourself insulin, you are estimating how many units of insulin it will take to process the carbohydrates you eat.
The University of California, San Francisco states that, as a general rule, 1 unit of insulin will process anywhere from 12 to 15 grams of carbohydrates and lower your blood sugar by about 50 milligrams per deciliter (mg/dL).
Since the human body is so complex, not all people will process insulin the same way. Factors like time of day, stress levels, and physical activity can make these numbers more difficult to predict.
Because of this, you’ll probably start off giving yourself insulin based on numbers for the average person. After seeing how these numbers help you manage your blood sugar, you may have to adjust based on how your body uniquely responds to the insulin you administer.
Now that you know the how and why behind insulin dosing, let’s consider how you may calculate your insulin needs.
You’ll usually give yourself an insulin dose around your meals since that’s when you take in carbohydrates. You also will typically check your blood sugar to see if you’re meeting your premeal target dose.
To calculate your insulin needs:
You may find that if you generally eat about the same amount of carbohydrates each day, you may be able to consistently inject the same amounts of insulin outside of special occasions. It takes time to find out how your body best responds to insulin.
Let’s say that you check your blood sugar before a meal and it’s 170. You’ll need 1 unit to adjust to your target of 120.
If you plan to eat a meal that has 60 grams of carbohydrates, you’ll need to give yourself 6 units of insulin to adjust for your meal.
This means you’ll need 7 units total.
If your child needs help learning to calculate their insulin needs, Children’s Healthcare of Atlanta has created a helpful worksheet just for this.
Remember, there are two components to insulin correction:
Combine both of these when considering how much insulin to inject.
For this chart, we’ll assume that your premeal blood sugar target is 120 mg/dL and that 1 unit will decrease your blood sugar by 50 points.
If your blood sugar is below 60, do not administer insulin. Instead, you should immediately consume 15 grams of carbohydrates.
If your blood sugar is 300 and above, check your ketones and contact your doctor immediately.
For this chart, we’ll assume that you take 1 unit of insulin for every 10 grams of carbohydrates.
How diabetes affects your body can vary greatly from person to person and day to day.
When establishing your insulin routine with your doctor, be sure to discuss your lifestyle honestly so they can help create the best plan for you. Your doctor might advise different calculations than those listed above to help fine-tune your dosage.
Many things can affect how your body processes carbohydrates and insulin. According to the American Diabetes Association, these include:
Managing your diabetes can cause many highs and lows. Both can represent a medical emergency. Call 911 or local emergency services if you experience the following:
Emergency signs of hyperglycemia (high blood sugar):
Emergency signs of hypoglycemia (low blood sugar):
Insulin has a narrow therapeutic index, which means there is a fine line between a beneficial dose and a harmful one.
It’s possible to overdose on insulin. In a review of insulin overdoses, excess dosages were reported as being anywhere from 26 to 4,800 units. Some of these were administered accidentally, which helps explain why the number is so high.
It’s important to know the symptoms of hypoglycemia in case you ever inject too much insulin. These include:
Contact your doctor if you’ve over-administered your insulin.
Ideally, you should be able to correct your blood sugar with an appropriate insulin dose. How much insulin is too much varies based on how sensitive your body is to insulin.
If you have higher-than-expected blood sugar (over 300), you should check your urine for ketones. The presence of ketones suggests your body’s cells are having trouble getting enough glucose. You could be at risk for a serious condition called diabetic ketoacidosis (DKA) if you have ketones in your urine.
In this instance, you need extra help correcting your blood sugar. You should seek emergency medical attention instead of trying to keep injecting insulin to lower your blood sugar.
Insulin will lower your blood sugar. If your blood sugar is already low, you shouldn’t inject more insulin.
Signs that your blood sugar is too low include sweating, dizziness, blurred vision, and significant fatigue. If this happens, try to consume rapid-acting carbohydrates, like sugared sodas, fruit juice, or glucose tablets, to get your blood sugar levels back up quickly.
You can calculate the amount of insulin you take before meals by considering your blood sugar before you eat and the number of carbohydrates you take in during your meal. Scroll up to see our sample calculation and example.
The average person will take about 1 unit of insulin for every 12 to 15 grams of carbohydrates consumed.
There is some variation to this, depending on how sensitive you are to insulin. For some people, this range is 1 unit for every 6 grams of carbohydrates, while for others, it’s 1 unit for every 30 grams of carbohydrates.
You will typically inject a longer-acting or basal insulin at night. This insulin will work as you sleep for (ideally) seven to eight hours. You should establish your basal insulin dose with your doctor.
You may adjust this dose on a regular basis depending on your blood sugar before bed.
Injecting insulin is not a safe approach to weight training. However, some bodybuilders will inject it as a performance-enhancing drug. They believe injecting insulin will allow energy in the form of glucose to enter their cells so they can build more muscle.
This practice is unsafe and can lead to severe and potentially life threatening hypoglycemia, according to 2019 research.
You should not take insulin unless you have diabetes. If you do have diabetes, talk with your doctor about how your training regimen may affect your blood sugar levels.
Human growth hormone (HGH) is another hormone that bodybuilders may inject in an attempt to gain muscle. Some bodybuilders will inject both HGH and insulin, according to 2017 research. This is an unsafe practice that doctors do not recommend.
It can take time to understand how your body best responds to insulin correction when you have diabetes.
Having a plan for regular dosage and knowing the signs of high and low blood sugar can help you safely manage your diabetes. If you have questions, contact your doctor to ensure you have the best plan for keeping your blood sugar under control.
Last medically reviewed on April 8, 2022
Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available.
Current Version
Apr 8, 2022
Rachel Nall, MSN, CRNA
Edited By
Rayne Whitington
Medically Reviewed By
Alan Carter, PharmD
Copy Edited By
Ahmed Fara
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