Using Insulin


I’ve been prescribed insulin and I am so confused!

Ok so you have been diagnosed with Type 1 diabetes and you have started insulin therapy.  Or, your Type 2 has progressed to the point where you need to begin insulin therapy.  (If this is the case, it is REALLY important for you to increase your efforts at lifestyle management to prevent further progression of your diabetes.  Please ask me for help.)

Before we begin, please note, that I recommend a low carb lifestyle for all people, but PARTICULARLY as a first line of defense in the treatment of diabetes, NOT drug therapy. (Why A Low Carb Diet Should Be the FIRST Approach in the Treatment of Type 2 Diabetes HERE.  Low Carb Diet Recommended for Type 1 and Type 2 Diabetes HERE.)

I believe that drug therapy has it’s place, but ONLY to address any issues after a healthy, low carb lifestyle, exercise and other lifestyle practices are ALREADY in place.  Now, for those with Type 1, there is no way to avoid insulin.  Insulin will be a requirement for life.  However, with a healthy low carb lifestyle, your insulin needs can be drastically reduced.  A low carb lifestyle will also help better regulate blood glucose, eliminating highs and life-threatening lows.  Many of those with Type 2 have been able to discontinue insulin usage with appropriate lifestyle management.

So, why are there so many insulins?  How do they work and how do I use them?

Well, in order to understand why there are so many types of insulin and why we need to use specific kinds for specific purposes, it is helpful to understand how natural insulin (“endogenous” insulin)  is made in the body of a person with a normally functioning pancreas.

First, our body likes to maintain a state of homeostasis at all times.  When we get hot, we sweat to cool ourselves down.  When we are tired and breathe shallow, our body prompts us to yawn to inflate our lungs and increase our oxygen intake.  When our blood glucose goes up, our body produces insulin to bring it down.  When our blood glucose is low, our body releases stored glucose from the liver to make it go back up.  Our body desires a constant state.

In that endeavor, the body releases small pulses of insulin all day long just to support its basic metabolic needs.  This has nothing to do with food.  In fact, if we were in bed with the flu and didn’t eat for 3 days, our body is still making small amounts of insulin to carry out its basic functions.

Then, when we eat, (or when we are sick, or when we have a stressful event, or any situation that raises blood glucose) our body releases a larger dose of insulin.

So, our pancreas only makes one type of insulin, but it releases it in different ways and for different purposes.

Well, with insulin injections (“exogenous” insulin), there is an attempt to mimic this pattern of the natural pancreas.  Therefore, different types of insulin are needed.

Basal Insulin

BASAL insulin is the type of insulin that is taken to mimic our constant, small insulin release.  Insulins in this category include Lantus, Levemir, Toujeo, Tresiba and Basaglar.  These are “long acting” insulins and are typically meant to last for an entire 24 hour day, although some don’t last quite that long and some last longer.  These are typically meant to be “peakless”, which means that they release steadily into the bloodstream over their duration of action.

“N” insulin (Humulin N or Novolin N) is often also used as a basal insulin, although its duration is only about 10-14 hours, which is why it is most often used twice daily.  The one caveat of “N” insulin is that it is not a “peakless” insulin.  About 4-10 hours (a very wide window), it has a “peak” which means it is most effective at that time, and there is a potential for low blood glucose.  It can be difficult to pin down exactly when that will occur.  For this reason, “N” insulin is not used as often.  However, since the standard basal analog insulins are often pricey, “N” remains a widely use treatment due to it’s lower cost.

Bolus Insulin

BOLUS insulin is designed to mimic our quick release of insulin in response to elevated blood glucose (ie. at meals).  Insulins in this category include Novolog, Humalog, Apidra and Admelog.  These insulins go to work quickly, within 5-15 minutes, which is why they should not be taken too long before a meal.  They “peak” or have their greatest effectiveness at 30-90 minutes and last for about 4-5 hours, which is why these insulins are typically taken 3 times per day with meals (or two times per day if you only eat two meals.)

“R” insulin, or Regular insulin is also used as a bolus insulin, although this insulin is considered “short acting” not rapid acting.  So you need to take it quite a bit earlier in advance of a meal, 30-60 minutes.  It “peaks” at about 2-3 hours and lasts 5-8 hours.  “R” insulin has been used less over the years because many people don’t have set mealtimes and are not sure when they are going to eat, therefore making insulin that has to be dosed 30-60 minutes ahead of time, more inconvenient.  However, “R” insulin still has a very useful purpose.  It too is less expensive, like “N” insulin.  It also is the only insulin approved for insulin drips in the hospital setting.

Mixed Insulins

So now the picture gets a little more complex, with mixed insulin usage.  For years, many people mixed “N” and “R” insulins in the same syringe for injection.  This is still being done and is perfectly safe to do.  “N” can also be mixed with rapid acting insulins.  However, keep in mind that “long acting” insulins (Lantus, Levemir, Toujeo, Treaiba and Basaglar) CANNOT be mixed with ANYTHING.  In fact, they shouldn’t even be injected too close to the same site as a rapid or short acting injection as it can affect how it works.

So, mixed insulins either contain “N” with “R” (Novolin 70/30, Humulin 50/50) or “N” with rapid acting (Novolog 70/30, Humalog 75/25 or Humalog 50/50).  In these formulations, the first number represents how much “N” you will get.  The second number represents how much short or rapid acting insulin you will get.  For instance, 70/30 is 70% N and 30% short or rapid acting.

Because “N” insulin is being used, mixed insulin is usually taken only twice per day.  It should always be taken before a meal, as it contains either short or rapid acting.  So, it is typically taken before breakfast and supper.

There are a few drawbacks to mixed insulin therapy.  First, you cannot change the percentages.  You get what you get.  Next, you only take the insulin twice daily, leaving your mid-day meal not covered.  Some make up for this by using a rapid or a short acting injection at lunch.  Next, with both “N” and short or rapid on board, there will be many “peaks” in the insulin delivery.  So the potential for low BG increases.  (Please read further about concerns with mixed insulin in my post “Problems with Mixed Insulin Therapy” HERE.)

Although I am not a huge fan of mixed insulin regimens due to the issues above, mixed insulin therapy still continues to have some benefits in terms of cost and convenience.  My recommendation to those that wish to use mixed insulin therapy is to do it the good old fashioned way of mixing your own so that you can tailor it to your specific needs.

But, once again, I have had many clients that are elderly and on a limited budget, with little assistance and limited dexterity who use mixed insulin pens with good success.  I have also had the same elderly patients with either cognitive issues or poor eyesight, that having both long acting and rapid acting pens in the home is a danger, as one can be confused for the other, leaving the potential for a life threatening situation.  So, it is nice that there are all types of inulins to fit all types of needs.

Insulin Concentrations

For many many years, insulin was only available in U-100 concentration.  That means that 1mL contains 100 unit of insulin.  Then came the U-500, which is 5 times concentrated, 500 units per mL.  This is particularly useful for people on large doses of insulin.  (However, with appropriate lifestyle management, use of this insulin would typically be completely unnecessary.)

Now there is U-200 (Humalog and Tresiba) and U-300 (Toujeo).  Once again, these are designed for people taking larger doses so that they will get more units in less volume.  It was seen that there may arise some confusion into the uses of U-200 and U-300 in determining how much to “draw up.”  In order to avoid any confusion and keep patients from overdosing on insulin, these concentrations come only in dial up pens to prevent error.

What is a “Carb Ratio” and How Do I Calculate It?

If you are on basal insulin only, you will not be using an insulin to carb ratio (or ICR).  A carb ratio is for those who are on both basal and bolus insulin.

When first being started on bolus insulin, your healthcare provider may prescribe a set dose of insulin at mealtimes to get a feel for how much insulin you need for your meals.  For instance, they may start you on 5 units of rapid or short acting insulin before each meal.

Later, they may wish you to learn how to “count” your carbs and give yourself varied doses of insulin, based on the amount of carbs you are eating at each meal.  This is a more accurate way of administering mealtime insulin, as it more closely mimics what your pancreas would have done for the meal.  In other words, eating more of the foods that raise your blood sugar warrants the administration of more insulin.

Your carb ratio is written as a, well, ratio.  For instance 1:15.  This means that you would give yourself 1 unit of insulin for every 15g of carbs being consumed.  Sometimes, we would just say that your carb ratio is “15” (instead of 1:15, as the “1” is assumed.)

How is a carb ratio calculated? 

To calculate a carb ratio, you will add up all the insulin you use in a day (basal and bolus).  Say you use 30 units of basal insulin at night and 5 units of bolus insulin at each meal.  This means you take a total of 45 units of insulin per day.

The formula for calculating a carb ratio is 450 (or some use the number 500) divided by the total daily dose.  So, 450 divided by 45 is 10.  You will take 1 unit of insulin for every 10g of carbs.  Your carb ratio is 1:10.

So, if you are having a meal with 10g of carbs, you will take 1 unit of insulin to cover those carbs.

Some people also wish to bolus insulin for protein as some of the protein we eat also can turn into glucose.   For those that I work with personally, I can instruct on protein bolusing.  Please contact me for more information.  This is NOT part of your insulin to CARB ratio.  This ratio is for carbs only.

Of course, it will be rare that you are eating EXACTLY 10 (or whatever your carb ratio is) grams of carbs.

To turn this into a formula for you, you will take the amount of carbs you are eating and divide it by your carb ratio.  Here is a better example.  25g of carbs divided by a carb ratio of 10 is 2.5 units of insulin.


What is an “Insulin Sensitivity Factor” and How Do I Calculate It?

If you are on basal insulin only, you will not be using an insulin sensitivity factor (or ISF).  A sensitivity factor is for those who are on both basal and bolus insulin.

When first being started on bolus insulin, your healthcare provider may prescribe a set dose of insulin at mealtimes to get a feel for how much bolus insulin you need.  For instance, they may start you on 5 units of rapid or short acting insulin before each meal.

However, throughout the day, you may experience elevations in your blood glucose, not particularly related to a meal, or for a meal bolus that was underestimated.  For instance, say you did your best to estimate carbs for a meal at a friends house, but you really weren’t sure how many carbs were in the meal.  Now, going into your next meal, you are still 30, 40, or 50 points above your target range.  Or what if your blood sugar is elevated for a different reason altogether?  Stress, poor sleep, hormones, you name it, there are a million reasons your blood sugar can be elevated, not related to food.  And we need a way to calculate how much insulin it will take to bring you back down to target.

Your sensitivity factor is also written as a ratio.  For instance 1:35.  This means that 1 unit of insulin should decrease your blood sugar by 35 points.  Sometimes, we would just say that your sensitivity is “35” (instead of 1:35, as the “1” is assumed.)

How is sensitivity factor calculated?

To calculate a sensitivity factor, you will add up all the insulin you use in a day (basal and bolus) .  Say you use 30 units of basal insulin at night and 5 units of bolus insulin at each meal.  This means you take a total of 45 units of insulin per day.

The formula for calculating a carb ratio is 1700 (or some use the number 1800) divided by the total daily dose.  So, 1700 divided by 45 is approximately 38.  So, each unit of insulin will reduce your blood sugar by 38 points.  Your sensitivity factor is 1:38.

So, if your target BG before meals is 85 and your blood sugar is 123, this means you are 38 points over your target.  You will give yourself 1 unit of insulin.

Of course, it will be rare that you are EXACTLY 38 (or whatever your sensitivity is) over your target.

To turn this into a formula for you, you will take your current BG – target BG divided by your sensitivity factor.  So, for instance, if your BG is 135 and your target is 85, you will do 135 minus 85 (which is 50) and divided it by 38.  You will take approximately 1.3 units of insulin.


Insulin Myths and Facts
  • MYTH: If I take insulin, I can eat whatever I want and just take more insulin.
  • TRUTH: Weight gain and increased insulin resistance will result from this practice. Also, there would be an increased chance of  highs and lows.  This is a dangerous practice.  Avoid it at all costs.
  • MYTH: Since I have Type 2 diabetes, I shouldn’t take insulin.
  • TRUTH: Type 2 is not a disease of insulin deficiency, but typically, especially initially, of insulin excess. Therefore, for those with Type 2, it is much better to manage diabetes with lifestyle FIRST AND FOREMOST (which normalizes both blood glucose and insulin levels).  Type 2 can actually be made worse by insulin, if you are already producing lots of it. However, there are cases where Type 2 progresses to an insulin deficiency.  Many find out about healthy lifestyle only after years and years of elevated blood glucose.  In these cases, significant damage has often been done that requires the use of medications, including insulin.  It is important that if you have sustained such damage, that you preserve your remaining insulin producing cells.  This often requires the use of insulin, sometimes for a short time, sometimes permanently.  However, the goal for those with Type 2 should be getting the absolute MAX benefit from lifestyle intervention and only use medication or insulin to make up for any deficiency that has resulted from prior damage.  Those with Type 2 should NOT be living with high blood glucose levels daily just to say they are “medicine free” while damage is being done to major organs.  So there is no “shame” in using insulin, if it is not being used to “cover” an unhealthy lifestyle.  Insulin should never be used to cover poor dietary choices.  With insulin use, the goal for Type 2 should be to use as little as possible and to reduce or eliminate its use if this can safely be done when normal blood glucose levels are reached.
  • MYTH: If I am a Type 1, my diet is irrelevant because I have to take insulin anyways. The amount doesn’t matter.
  • TRUTH: The importance of lifestyle management of Type 1 is AS IMPORTANT as Type 2, it is just that total insulin elimination will not be possible. However, this should not be viewed as an excuse to eat just any type of diet.  Permanent complications of diabetes comes with both elevated blood glucose and elevated insulin levels.  In fact, many with Type 1, also show evidence of Type 2 (insulin resistance) when they do not manage their lifestyle with a healthy diet.   It is best to keep both blood glucose and insulin levels normal and steady.  This can ONLY be accomplished with diligent lifestyle management.
Tips for Insulin Use
  • Only inject insulin on cleansed skin
  • Rotate your injections sites with each injection
  • Gently rotate all mixed insulins
  • Draw up or dial up insulin
  • Inject subcutaneously
  • Hold for 5-8 seconds after injection
  • Store unopened insulin in refrigerator
  • Refrigeration is not required after opening
  • Insulin expires in 28 days from opening (45 days for Levemir, 56 days for Tresiba)

Once again, if you have Type 2 and have been prescribed insulin, please read this site well to see how you can reduce or eliminate your need for insulin.  If you have Type 1 and would like to reduce your insulin usage and rid yourself of severe episodes of hypoglycemia, as well as reduce your risk of serious complications, this site can help you.


Helpful video on drawing up and administering insulin with a syringe


Helpful  video on mixing insulin


Helpful video on using insulin pens