Why and when do you need insulin?

This is covered in more detail. Insulin is one of the most important of your body's hormones. Normally it is made in the pancreas, and is secreted into the blood stream. From the blood the insulin travels to muscles and other tissues.

In the muscle cell it acts as a 'door opener' and lets glucose pass from the bloodstream into the muscle cell. The muscle cell stores the glucose for use later. Some glucose is used for energy, and excess glucose is converted to fat.

Without insulin, your muscle has no energy stores to use, so you become very weak. In addition, because the sugar is not used up it reaches very high levels in the bloodstream. This can be very dangerous and needs treatment in hospital, and is called diabetic ketoacidosis.

In the longer term high levels, over years, are poisonous to the body. Intensive control helps Jama 15   AJO 15


Insulin with food

The normal pancreas secretes half its insulin as a 'bolus' after eating. To replace this insulin you need a quick acting insulin. This dose of insulin has to match the amount of food you eat, and particularly the amount of carbohydrate.. Adjusting insulin for carbohydrate.   Detail  I


Basal insulin requirement

The normal pancreas secretes the other half of the insulin gradually during the day and night, the so called 'basal' secretion. To replace this insulin, you need insulin a long acting insulin to work when you are not eating. You need much less insulin when you exercise, because exercise allows glucose to enter the muscle cell for immediate use (exercise acts 'like' insulin). Detail


Type 1 and Type 2 diabetes

Type 1 diabetics have very little insulin remaining, and can get severe problems without insulin. See below.

People who have type 2 diabetes and still need insulin should read the type 2 page as well as this page: not being overweight and plenty of exercise if at all possible is important. If the pancreas produces no insulin, effectively the diabetes can be treated as type 1.

But if the pancreas still secretes a moderate amount of insulin, certain problems are less common, such as hypos. Normally, the pancreas produces less and less insulin, so after many years of type 2 diabetes, hypos and other problems become a lot more common.


Basic insulin rules

  1. Without insulin you become weak, your sugar levels rise, and the high sugar level damages your body. You are diabetic when your 'natural' insulin runs out. Here we assume you need insulin for your diabetes, so you have type 1, or type 2 diabetes with no remaing insulin production from your pancreas.
  2. You need half your insulin throughout the day, the other half when you eat.
  3. There are  different insulins. Some act very quickly and the effect wears off (rapid-acting) , others more slowly and their effect continues (long-acting. You need the first for meals, and the long acting for your basic requirement. Insulin pupms just use one type of rapid acting insulin. If you have lots of medical problems you may be offered a combined (a mixture) insulin.
  4. Your will always need insulin. Even if you are ill and not eating (a serious situation: you need to call your doctor or go to hospital).
  5. You generally need more insulin if you have an infection, and can reduce the dose as you get better. If you have an infection your sugar levels rise. People with diabetes often need antibiotics for infections, so see your doctor to see if you need some.
    You are in the best place to adjust your insulin as your sugar rises with the infection. Your practice nurse can usually advise you if you do not know what to do.
  6. If your sugar rises for no apparent reason you may have a hidden infection, such as a chest or urinary tract infection. Also, as soon as the infection gets better your sugar levels drop, so you will need less insulin. If you do not reduce your insulin levels in time you may notice hypos.
  7. You need to test your sugar regularly, usually 4-6 times a day for good control, less often if you are elderly and do not need such tight control. Glucose sensors are ideal : Freestyle or Dexcom.
  8. You are at risk of hypos (when the sugar goes low) and will need to treat the hypo, perhaps with orange juice and a banana. You need to read and learn about hypos, as for each hypo you notice you are getting two others. A serious hypo is a coma when you become unconscious.
  9. You need to keep your insulin in a cool safe place, have a spare supply, have some identification to indicate to others that you are diabetic (for instance, if you are in a coma this will help to tell people why and what they should do).
  10. Glucagon  injections may help if you have hypos.
  11. see the hypos page
  12. driving..you should test glucose levels before start driving and every 90 minutes
  13. exercise.. other than moderate activity for a short time, you should similarly test more
  14. It is important to attend  a DAFNE program or equivalent, to learn how to control the diabetes well.
  15. Help must be available from the diabetes care team to enable patients to achieve good diabetic control NICE 15.
  16. The general HbA1c target is 48mmol/mol (6.5%).
  17. your diabetes team should provide a walk in and telephone service during working hours
  18. a 24 hour helpline
  19. HbA1c should be tested every  3-6 months
  20. pancreas transplant may help if you have very severe hypos, or related problems


Controlling your diabetes, day to day

You have to test you blood glucose detail , and aim for

See when to test. Keeping to these glucose levels is a problem for many patients. See shift work; driving. High levels of glucose levels cause the diabetic complications, such as retinopathy. People needing insulin have a choice..taking action to keep low glucose levels, or having more complications.

Blood glucose levels should be tested 4 times a day, or more often if NICE 15,  or use a sensor is much better. You should test or read the sensor frequently if


Controlling your diabetes, long term checks

Detail   The HbA1c test can tell you you your diabetes has been controlled over the previous 10 weeks. See  

Glucose sticks to the red blood cells and tissues of the body. The higher the blood glucose, the greater amount of glucose that attaches to the blood cells and tissues. The more glucose that is attached, the greater the risk of diabetic complications.

HbA1c measures the amount of glucose attached to the red blood cells The HbA1c gives a good guide to the blood glucose level over the previous 8-10 weeks. It is used as a measure of long-term measure of diabetic control. The usual result in someone without diabetes is 27-42 mmol/l ( 4.0-6.0%).

The best result in diabetes is 42-58 mmol/mol (6.0-7.5%). At this level most long term complications can be prevented, whilst at the same time avoiding severe hypos (hypoglycaemia). Below this level there is a higher risk of a bad hypos. Above this level here is an increased risk of complications. Before conception and during pregnancy, slightly lower levels are preferred.

The HbA1c is not the same as the average blood glucose is always slightly lower. For example, someone who has a blood glucose ~17mmol/l with have an HbA1c of ~120mmol/l  (13%) . Convert HbA1c to glucose.


Adjusting dose of insulin with food

If you are going to control your diabetes well, and keep low blood sugars as above, the dose of insulin has to be adjusted with food.


high gycaemic foods produce glucose spikes, and are harmful

a low fibre meal with cakes etc. will cause a rapid rise in sugar whatever insulin you use, and the high levels damage your body (in practice sugar levels may be higher than shown here)


Adjusting long acting insulin

It is hard to know whether high/low glucose levels are due to the quick acting or long acting insulin. Here are some ideas.


Hypos and tight control

dancing in diabetes

Trying to lower your HbA1C to improve your control may mean more hypos (episodes of low blood sugar, <4mmol/l). Hypos are explained in detail on the hypo page.

You need to be prepared, to know what to do, to avoid hypos. Learn to monitor your blood sugar, and learn to adjust your diet and insulin according to the blood sugar level.


Hypo warning symptoms
  • shaky, tremors
  • sweaty
  • hot
  • cold
  • very hungry
  • drowsy
  • convulsions
  • confusion
  • anger, irritation
  • running away
  • laughing, silliness
  • palpitations
  • high stress/emotions
  • an early morning headache like a hangover


If you are getting hypos it is best to eat regularly and control your diabetes well, and only then gradually learn to change your eating patterns as you wish, yet still control your diabetes.

Try and work out the cause of the hypo, and if you think you can find the cause take corrective action.

It is naturally stressful trying to achieve good control, and can be disappointing when you get a hypo. This is a real challenge, but if you can take it on, with the help of your specialist nurse, friends, and others, then the results can be very worthwhile.
Really you need to find the lowest HbA1c that still allows you not to have any hypos.

Research suggests pumps may be helpful if you have trouble reaching levels less than 8% / 64mmol/l, but they only lower the HbA1c 5mmol/l / 0.5% on average.

If you are still getting lots of hypos and cannot control your diabetes, and Islet cell transplant may help.

Night time hypos

To prevent night time hypos, aim for a sugar above 6 mmol/l at 10pm, before bed detail.



Indeed, if you are pregnant and use insulin you need slightly different advice than is on this page, and must be extra careful. Normally if pregnant you need a complex carbohydrate snack before you go to sleep, and specialist advice. See retinopathy in pregnancy.



Detail.  These are a real problem...all of a sudden, without any warning, sugar levels can drop and you can become unconscious. Hypo-unawareness  suggest you  care getting may hypos and have lost your warnings as above. This page  tells you what you can do to get them back, but it is essential to get advice from your diabetes nurse and doctor. For every hypo you notice, research has shown you are likely to be having 2 others. For professionals.

graph of glucose fluctuations with hypo-unawareness

Fluctuating sugar levels may occur if your diabetes is not well controlled; you only notice one out of 3 hypos


Diabetes education programs

At last the NHS has started running these programs in many parts of the country,



People with diabetes face some tremendous problems. If you are trying to achieve better control, perhaps advised to do so by an ophthalmologist, in theory it may be best to change the type of insulin you use (see some examples above). In practice if there is a lot going on in your life, this may not be a good time. For instance, it is not ideal to change insulin if you are moving house, job, or changing partner.

Generally you need advice from your diabetes nurse before changing. This is particularly so if the type of insulin is new to you, or if the pen device for injection is different from that you have used previously. You will need on-going advice, and need to be able to phone for advice when problems develop.


Autonomic neuropathy

The autonomic nervous system controls automatic bodily functions, such as how the bowels work and how we sweat to cool our bodies. Normally a low blood sugar makes you feel sweaty and trembly, and this feeling can tell you your sugar is too low, and you need some food. If this system becomes damaged you are said to have  autonomic-neuropathy    

High sugar levels from diabetes may cause this condition. It normally develops after many years of diabetes.

Unfortunately if you have 'autonomic neuropathy' and other changes from diabetes you may not notice your sugar is low. So if you have a hypo you would normally feel sweaty and shaky, but if you have this neuropathy you may not feel anything, and so the hypo will go unnoticed. However, the low sugar will affect your brain, and you will not be able to think clearly or drive safely. This is called 'masking' of hypos or 'unawareness'.

Unexplained diarrhoea is commonly caused by autonomic neuropathy.

These changes can make your diabetes difficult to control. This is one of the 'catch 22' situations of diabetes, you need a low sugar to prevent complications, but the complications (which include the neuropathy) prevent you achieving the levels you need. A lot of research is taking place to address these issues, but it does not make life easy if you have them. To prevent more hypos, testing your sugar regularly and using the results to adjust your insulin is the only way to prevent or slow down diabetic complications. If you have hypo unawareness and have low sugars without knowing, this indicates you are probably getting frequent hypos, with the result that your body's reaction to them wears
To correct this you really need expert advice from you diabetes specialist nurse, but this is what one patient was advised