Insulin for people with Type 1 diabetes

Your insulin therapy can be tailored to fit with your own particular lifestyle.

This section provides some information about insulin. If you are newly diagnosed with Type 1 diabetes or you are thinking about making a change to your current insulin, always work closely with your specialist diabetes team.

When you have Type 1 diabetes your body can't produce its own insulin. Insulin is a body hormone and it needs to circulate in your blood stream to do its job properly. If you don't have enough insulin your body is unable to use or store glucose properly. When you have Type 1 diabetes you need to take your insulin by injection (under the skin).

Many people wonder why it is not possible to take insulin as a tablet. Insulin can't be taken as a tablet, because when it is, it gets broken down in your gut and ceases to be insulin.

In some countries research has been done into giving insulin in an inhaled form (similar to an inhaler used for asthma drugs). This has been somewhat successful, but there are still problems with this system and it is not widely available commercially.

Most people feel very anxious when they first find out they need to start taking insulin. But with support this initial hurdle is usually manageable.

Nowadays the insulin needles are so short and fine that nearly everyone finds that their insulin injections are far more comfortable than finger pricks. Insulin injections go just under your skin and not into a vein.

People often feel very much more well and energetic once they get established on insulin. They have often been short of their own insulin for a very long time and this has made them feel unwell, tired, and often prone to all sorts of infections.

What is insulin and where does it come from?

Insulin is a hormone. It occurs naturally in the human body. The insulin that you get from the chemist is what is called 'human insulin'. Many years ago insulin for injection came from pigs or cows and was called 'porcine insulin' or 'bovine insulin'.

Human insulin is manufactured in the laboratory. It is made by cell organisms (e.g., yeast or Ecoli cells) that have had the human gene for making insulin spliced into them. These cells then busily make insulin. This human insulin is a very safe product to take and there have been no instances of insulin becoming contaminated with anything harmful.

Basal insulin

The low level of insulin that your body needs all the time is called 'basal insulin' or 'background insulin'. This constant low level of insulin keeps several body processes in balance.

One of these processes relates to your liver. Your liver is an organ that is able to make extra glucose to release into your blood stream. It does this when it is 'told' to do so. The two main things that tell your liver to make extra glucose are either:

• When your level of insulin gets very low; or
• When your level of stress hormones gets high

So, one of the main things your basal (or 'background') insulin does, is to stop your liver making too much glucose. If you think of your liver as a potential glucose factory, you can think of your basal insulin as keeping a lid on that factory. If you don't have enough basal insulin, the lid gets loose and extra glucose starts escaping from your liver into your bloodstream. And so your blood glucose levels start to get too high. This is why your blood glucose levels can go up over night even if you have not eaten anything (because of your liver making glucose).

On the other hand, if you have too much basal insulin, it can cause your blood glucose level to go too low. This is because it dampens down your liver's ability to make glucose by too much. It also causes your blood glucose to be moved out into your cells and muscles and be burnt up too quickly.

In practice this means that managing your basal insulin at the right level is quite a balancing act.

Insulin by injection comes in different types. These types are defined by their length of action in the body (the length of time they remain in your body). 'Intermediate' or 'long' acting insulins are normally used to give your body its basal supply of insulin. In actual fact the vast majority of people use intermediate-acting insulin to give them a basal level of insulin. The long-acting insulins are not often used now.

Intermediate acting insulin is used for supplying your basal needs because it is absorbed slowly over a 24-hour period. It does have a 'peak' absorption period however. This peak absorption period is not ideal for basal insulin requirements because it's better for your body to get a consistent and 'flatter' dose over time. New intermediate-acting insulins have been developed that have a flat, peakless absorption profile. They are available in some countries, but unfortunately, these insulins are not yet available in New Zealand.

Some people take a single daily dose of intermediate insulin to provide their basal requirements. Others take intermediate-acting insulin twice a day (about 12 hours apart) for their basal needs.

The only exception to using intermediate or long-acting insulin for basal insulin needs is if you deliver your insulin via an insulin pump. An insulin pump is always loaded with either short or very-short-acting insulin. It delivers this insulin in such a way that it acts as basal insulin. That is, the insulin is delivered in very tiny but constant and uninterrupted amounts. So you have a constant but low dose of insulin.

Spurts of insulin ('bolus' insulin)

Your body needs basal insulin to help maintain a steady blood glucose level, not too high or too low. But it also needs spurts of insulin (or 'boluses' of insulin) to give you extra insulin on top of your basal insulin when you need it.

When do you need spurts of insulin?

When you eat. When you eat carbohydrate food your body converts the carbohydrate into glucose and absorbs it into your blood stream.
You need extra insulin to process this extra blood glucose. The processing of this glucose means either moving it into your body cells to get burnt as energy OR moving it into your body cells to be stored as extra glucose for when you need it (e.g., for when you are exercising). Stored glucose is called 'glycogen'. Your extra spurts of insulin perform both these tasks; enabling glucose to be both stored and used.

The insulin you use to give your body the extra spurts of insulin when you eat is either short-acting insulin or very-short-acting insulin.

Short-acting insulin (e.g., Actrapid or Humulin R)

Short-acting insulin has an absorption profile that slightly extends beyond the blood glucose profile that your body has after it eats a meal. Because of this, if you are using short-acting insulin for your meals, you generally need to eat a small snack 2 - 3 hours after the meal. Why? To provide enough glucose for the tail end of your short-acting insulin to work on.

Short-acting insulin also acts best if you take it 15 - 20 minutes before you eat. This is because it takes this long to start being absorbed. It has a better chance of matching your post-meal blood glucose profile if you give it a head start.

Very short-acting insulin (e.g., Humalog or NovoRapid)

Very short-acting insulin is also used to give you spurts of insulin for processing the glucose you get from food. Very short-acting insulin wears off sooner than short-acting insulin. This means that you usually don't need to have an extra snack after your meal to cover the action of very short-acting insulin. It is also absorbed much more quickly than short-acting insulin. So, instead of needing to take it 20 minutes before food, you can take it with your food (or even immediately after food).

What types of insulin are currently available in New Zealand?

There are two different brands of insulin available in New Zealand. You can get Novo Nordisk insulin or Eli Lilly insulin.

The insulins that are currently available within these brands are divided into four main types. These are defined by how long the insulin takes to be absorbed into your blood stream from under your skin, and how long it continues to act in your body.

The four types are:

Very short-acting insulin (Humalog or Novorapid)

Short-acting insulin (Actrapid or Humulin R)

Intermediate-acting insulin (Protaphane, Monotard, HumulinN or HumulinL)

Very long-acting insulin (Ultratard or Humulin U)

Some of the above insulins are available in pre-made mixtures, where an intermediate-acting insulin is mixed with a short-acting insulin.

These premixes come in varying combinations, or ratios, between the short and intermediate insulin. The premixes are always labeled by how much of the mixture is short-acting insulin. For example, a mix called 'pen mix 30' will have 30% short-acting insulin in it and 70% intermediate-acting insulin in it. A mix called 'mixtard 50' will contain 50% short-acting insulin and 50% intermediate-acting insulin.

Pre-mixed profile

What determines what type of insulin I take, and the times I take it?

A number of factors will determine this. These factors are likely to be:

• Whether you are newly diagnosed with Type 1 diabetes. Many diabetes services have preferred ways of helping people get started on insulin. Some prefer to help you start on a once or twice daily dose of intermediate-acting insulin only. Others prefer to immediately help you onto what is called a more 'intensive' way of taking insulin, that is, a four times daily dose using a combination of both short and intermediate-acting insulin. Your diabetes service will discuss the way they recommend with you.

• Whether you are in the 'honeymoon phase' of your diabetes. For a period after you first start on insulin you may have very low requirements for injected insulin. This is because your pancreas will still be making quite a lot of its own insulin.

  This period is often called 'the honeymoon phase'. During this time you may need very little, and sometimes occasionally no, injected insulin. But the natural process of Type 1 diabetes means that eventually your own production of insulin will be either zero, or very little. The less insulin you produce yourself, the more insulin you'll need by injection.

• What your blood glucose profile is (i.e., the pattern of how your blood glucose levels vary during the day). The times of the day that your blood glucose levels are highest or lowest will influence the type of insulin that your health professional will recommend to you.

• Your lifestyle needs. As you become established on insulin you will work closely with your diabetes team to get onto a way of taking insulin, and using types of insulin, that best allow you to have the sort of lifestyle you want.

• Your budget. Taking insulin by pump is usually an expensive option in New Zealand.

What are some of the common insulin 'regimes' (or ways of taking insulin)?

There are a number of different ways to take insulin. These ways fall into broad groupings, but each person is an individual and you will work out a way to take your insulin that works best for you, with the help of your specialist diabetes team.

The way of taking insulin that best works for you depends on your lifestyle and the length of time you've had your diabetes. If you are early on in your diagnosis of Type 1 diabetes you may be able to manage on a single dose of insulin daily. But eventually you will come to need your insulin in one of the following ways, or a variation on it.

Twice daily mixed dose

This is when you take your insulin before breakfast and before your evening meal. You take a mixture of short-acting (or very short-acting) insulin and intermediate-acting insulin at these times. You and your diabetes team will work out what dosage of each of these insulins is best for you.

If your life is quite regular this way of taking insulin can suit you very well. It's disadvantage is that it is inflexible. When you take your insulin this way you are committed to having your lunchtime meal within a fairly tight timeframe. This is because you have a dose of intermediate-acting insulin that you took at breakfast time getting strongly absorbed (or 'peaking') around lunchtime. If your lunch is delayed this insulin can make your blood glucose go very low.

Also, you can't change your insulin dose at lunchtime if you need to. For example, if you plan to eat a larger lunch than normal. This is because, using this method of taking insulin, you are not taking any insulin at the actual time of your lunch (you are relying on the peak of your pre-breakfast intermediate-acting insulin to cover this meal).

Four times daily (or 'basal bolus') using short-acting insulin

Here you have a dose of short-acting insulin before each of your main meals (breakfast, lunch and tea) coupled with a dose of intermediate-acting insulin (usually before bed or at your evening meal time).

This is often a very successful way of taking insulin because:

• You have more leeway in the timing of all of your meals (because your intermediate-acting insulin is not peaking during the day)
• You can make frequent adjustments to your short acting insulin. These adjustments may be in response to the amount of food you are planning to eat, the amount of exercise you are planning to get, or what your blood glucose is at the time you are testing your blood glucose and taking your insulin

Its main disadvantage is that you usually need to take snacks between your main meals. This is because the short-acting insulin you take at meals lasts for 5 - 6 hours. If you miss between meal snacks the tail end of this insulin can cause you to have a low blood glucose level at these times.

Four or five times daily (or 'basal bolus') using very short acting insulin: This involves taking a dose of very short-acting insulin before all your main meals (and also any large snacks) and either one or two doses of intermediate-acting insulin at either end of the day (breakfast and/or dinner or bedtime).

Taking your insulin in this way can offer you lots of flexibility. Because the insulin you are taking before your meals is very short-acting there is usually no need to have snacks between your meals. The peak of the insulin more closely matches the peak of blood glucose that you get after a meal.

You have the same flexibility of meal times that you have with 'basal bolus' using short-acting insulin. Because the very short-acting insulin wears off within 2 - 4 hours you can also use it to dose for larger snacks (more than
10 grams of carbohydrate). Very short-acting insulin is also just as effective if taken with your meal (rather than 15 - 20 minutes before your meal as with short-acting insulin).

Pumping insulin (or 'continuous sub-cutaneous insulin infusion' CSII)

In this way of taking insulin you use an insulin pump (which is attached by a very thin flexible tube to a soft plastic needle that sits under your skin) to deliver a low level of short-acting (or very short-acting) insulin continuously. This insulin provides for your basal insulin needs.

Giving your basal insulin in this way means that you have a lot of control over the amounts of basal insulin you are getting. You can program your pump to deliver varying 'basal rates' throughout the day. You can also temporarily reduce or increase your basal rates if need be. For example, you may want to reduce your basal rate if you are exercising (exercise makes your body more sensitive to insulin), or you may want to increase your basal rates when you are sick (being sick normally makes your body resistant to the action of insulin, so you need higher doses).

Over and above your basal rates you can use your pump to deliver boluses (or short bursts) of insulin when you eat. You can program these short bursts to be delivered immediately (if you are eating a normal meal) or over a longer period of time if you are taking a longer time to eat your meal (e.g., if you are eating out).

Learning how to use a pump for your insulin is quite involved. You will need to be able to commit to a long period of working closely with your diabetes nurse educator, your diabetes medical specialist, and your diabetes dietician in order to develop the skills and knowledge to manage on this way of taking insulin. But once you have the skills, using a pump can give you the most flexibility in terms of lifestyle choices out of any of the current systems or methods for delivering insulin.

Insulin devices

There are four devices available by which you can deliver your insulin:

Disposable insulin syringe

There are a number of different insulin syringes available. There are three different sizes: 30 unit, 50 unit or 100 unit. The size people choose often depends on the dose of insulin they use. If you are taking 62 units of insulin, then obviously a 30 unit or 50 unit syringe won't be big enough for you to use.
The length and fineness of the needles on insulin syringes varies also. The length varies from 12.7mm to 5mm. Generally if you are overweight a longer syringe needle will be best (remember even the longest syringe needle is still very short!).

The fineness varies from 29 gauge to 31 gauge. These are both extremely fine gauge needles. The higher the gauge number the finer the needle.

Syringes are useful for people who need to mix two different sorts of insulin into the same syringe. For example, a person might need to take 20 units of intermediate-acting insulin with their evening meal but also take 4 - 8 units of short-acting insulin at the same time. Mixing this dose into one syringe allows them to have one injection at this time instead of two.

A lot of young children have their insulin by syringe. This is because they are often taking their insulin twice a day (to avoid having to take insulin at lunch time when at school), and the dose is often a mix of intermediate- and short-acting insulin. So insulin syringes work very well for them.

It's quite safe to reuse your insulin syringe up to seven times; provided it is only used on yourself and that it is kept clean and in a safe place. You are entitled to 29 free syringes every three months. Your doctor needs to prescribe your syringes with your insulin and they will be issued by your pharmacy. You can also purchase extra syringes either from your pharmacy or from Diabetes New Zealand Shop.

Insulin pens

Insulin pens are devices that look similar to a rather heavy-duty fountain or ink pen. You load them with a cartridge of insulin and they have a short needle on the end of them (covered by their lid except when in use) that allows you to use them to inject your insulin.

Many people like pens because they are a very discrete way to take your insulin. When using a pen it is possible to take your insulin in a crowded room and for no one to notice that you have done so.

There are currently two brands of insulin pens available in New Zealand. They are Humapens (provided by Eli Lilly) and Novo pens (provided by Novo Nordisk). The Novo pen only fits Novo Nordisk insulin. The Humapen only fits Eli Lilly insulin. Both these insulin companies provide your pen (or pens) free of charge. For more on pens see pens, pumps and meters.

There are a range of pen needles to fit on the end of your insulin pen. They are all very short and fine. All the pen needles can be used interchangeably on both types of pens. See the Diabetes New Zealand Shop for pen needles.

Some premixed insulins (mixtures of short-acting and intermediate-acting insulin) come in cartridges that can be fitted into an insulin pen.

Pen Mate or Injectease devices

These two devices are designed to be loaded with either an insulin pen (pen mate) or an insulin syringe (Injectease).
Once loaded the devices have a button that automatically fires the needle into your skin. Some people who are very anxious about needles find these devices helpful (young children, for example). However, they are quite bulky and if you are able to use a pen or a syringe direct it is usually much easier long-term if you do so.

Insulin pumps

Insulin pumps are small devices that look very much like a pager. You load them with a syringe full of either short-acting, or very short-acting insulin. This syringe of insulin is connected to a length of fine plastic tubing which in turn is connected to a very fine cannula (or plastic needle) that is secured under your skin. When you are on a pump you change this cannula every 1 - 3 days.

Insulin pumps cost around $6000. You also have to pay for the tubing they use and this usually costs between $100 - 300 per month. The Ministry of Health does provide some insulin pumps free of cost along with meeting the ongoing cost of the disposable tubing. If you think a pump would be good for you talk with your diabetes nurse educator and diabetes medical specialist about the criteria you need to meet to qualify for a free pump.