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.

Please remember

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.

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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.

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:

  • Basal insulin dose. A basal insulin dose is an amount that you give yourself daily regardless of the foods you eat.
  • Bolus insulin dose. A bolus insulin dose helps correct or anticipate the carbohydrates you eat throughout the day. You will usually correct this with a bolus dose of rapid-acting insulin.

Calculating 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 rapid-acting insulin will process anywhere from 12 to 15 grams of carbohydrates.

A bolus dose may also be used to correct high blood sugar. In general, 1 unit of insulin lowers 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.

Putting it all together

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 calculate your insulin needs:

  1. Check your blood sugar level before a meal.
    • If your blood sugar level is in your target range, you do not need to calculate for extra insulin.
    • If your blood sugar level is higher than your target range (usually around 120), calculate how much insulin you’ll need. You should talk with your doctor about this, but usually, 1 unit of fast-acting insulin will bring your levels down by 50 points.
  2. Calculate the number of carbohydrates you’re about to eat. You can usually estimate these using carbohydrate counters.
    • For every 12-15 grams of carbohydrates, give yourself 1 unit of rapid-acting insulin. Ask your doctor if this number may be different for you.
  3. Add the number of units needed to adjust for both your target range and meal.
  4. Administer the total units of insulin.

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 look at an example

Let’s say that you check your blood sugar before a meal and it’s 170. You’ll need 1 unit of fast-acting insulin 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.

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Remember, there are two components to insulin correction:

  • your blood sugar levels before your meal
  • corrections for the carbohydrates you eat

Combine both of these when considering how much insulin to inject.

Insulin dose chart for blood sugar correction

For this chart, we’ll assume that your premeal blood sugar target is 120 mg/dL and that 1 unit of fast-acting insulin will decrease your blood sugar by 50 points.

Blood glucose 60–120 120–170 170–220 220–270 270–300
Insulin correction0 units 1 unit 2 units 3 units 4 units

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.

Bolus insulin dose chart

For this chart, we’ll assume that you take 1 unit of rapid-acting insulin for every 15 grams of carbohydrates.

Carbs in meal0–1516–3031–4546–6061–7576–9091–105106–120121–135136–150
Insulin correction1 unit2 units3 units4 units5 units6 units7 units8 units9 units10 units

The amount of rapid-acting insulin needed to process the carbs you eat is known as the insulin-to-carb (I:C) ratio. Learn more about the I:C ratio here.

Other factors

How diabetes affects your body can vary greatly from person to person and day to day and whether your diabetes is type 1 or type 2.

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:

  • your injection site and how often you vary it
  • when you take your insulin throughout the day
  • what your typical diet and caloric intake is like
  • how often you exercise
  • your stress levels
  • other chronic conditions or illnesses you may have

Is this an emergency?

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):

  • blood sugar that stays low even after taking glucose tablets or otherwise trying to raise it
  • dizziness
  • headache
  • shakiness
  • sweating
  • weakness
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How much insulin is too much?

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:

  • dizziness
  • sweating
  • anxiety
  • headache
  • blurred vision

Contact your doctor if you’ve over-administered your insulin.

How much insulin is too much to take for high blood sugar?

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.

Patience is key. Although insulin starts to work quickly, it takes time before you’ll see the full effect. Continuously trying to inject insulin may be unhelpful and potentially even harmful. Work with your doctor to learn to calculate how much insulin you need, and follow your treatment plan.

Here are some tips to help you understand when you’ll see an effect after taking insulin. Remember, these are general guidelines. You should follow the treatment plan recommended by your doctor.

Insulin typeStarts to work afterPeak effect afterTotal active time
Rapid-acting5-15 minutes1-2 hours4-6 hours
Regular30 minutes-1 hour2-4 hoursaround 4 hours, depending on dosage

Another factor to keep in mind is the 1:50 correction ratio. In general, correcting high blood sugar by 50 mg/dL uses 1 unit of insulin.

This correction ratio — also known as the insulin sensitivity factor — can vary for different people or in different situations.

You can calculate your insulin sensitivity factor based on the type of insulin you use (regular or rapid-acting) and how many units you use per day. View a calculation example here.

It’s important to know that these calculations may not apply to every situation. Your insulin needs can vary based on a variety of factors. For more information, talk with your doctor.

What happens when your body doesn’t have enough insulin to process glucose?

When your insulin levels are low, your body may need to use fat for energy, instead of glucose. Breaking down fat can cause ketones to build up in your body.

Whenever you’re sick or you have higher-than-expected blood sugar (over 240 mg/dL), you should check your urine or blood for ketones. Your doctor may recommend testing for ketones at other times, too.

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 or blood.

Signs of diabetic ketoacidosis (DKA)

Early symptoms of DKA include:

DKA can get worse quickly. Severe symptoms include:

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DKA is serious and can be life threatening. It must be treated by a doctor.

You should test for ketones if you have any symptoms of DKA.

If you have moderate or high ketones, call your doctor. If you can’t reach your doctor and you’re having any of the following symptoms, call 911 or go to the nearest emergency room:

How much insulin should I take for low 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.

People who use insulin or sulfonylurea medications to manage blood sugar should consider having a glucagon emergency kit on hand at all times. It’s a nasal spray or injection that treats severe hypoglycemia.

With severe hypoglycemia, you usually can’t swallow drinks or foods with glucose. Instead, glucagon treatment is used to raise your blood sugar level.

Glucagon emergency kits are available by prescription. If you don’t have a kit already, talk with your doctor about getting one.

You’ll want to teach your friends and family how to administer glucagon, because it’s often not possible to use it yourself during a severe hypoglycemic event.

If a person has a seizure, experiences decreased consciousness, or faints due to low blood sugar, call 911.

How much insulin to take before meals?

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.

How much insulin to take per carb?

The average person will take about 1 unit of fast acting insulin for every 12 to 15 grams of carbohydrates consumed.

There is some variation to this, depending on factors such as 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. This value is known as the insulin-to-carb (I:C) ratio.

Your doctor can help you learn the I:C ratio that’s suitable for you.

How much insulin to take at night?

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.

How much insulin to take for bodybuilding?

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.

How much insulin to take with HGH?

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.