How and when to take short-acting insulin - Brand names: Actrapid, Humulin S

Dosage

Short-acting insulin contains 100 units of insulin per 1ml of liquid.

You'll usually take a dose of short-acting insulin around 30 minutes before each meal. Your doctor or diabetes nurse will advise you on when to take it. The timing may depend on which brand you take. See what timing works best for you and try to stick to it as closely as possible.

Taking it before meals means that your levels of insulin are highest as your body absorbs glucose from the meal, which helps to stop your glucose level from going too high.

Your doctor or diabetes nurse will tell you how many units of insulin you'll need to take. You'll usually need to calculate your dose depending on the amount of carbohydrate food (sugar and starches) in each meal. This is known as carb counting. If you have type 1 diabetes you'll be given training in how to do this.

The dose of short-acting insulin you need also depends on:

• your weight
• the type of diabetes you have
• how active you are
• whether you're taking other medicines for diabetes

Changes to your dose

As well as adjusting your dose for what you eat, you may also need to change your dose:

• when you're ill
• if you're stressed
• in hot or cold weather
• if you're doing exercise
• when you start or stop some medicines
• during the menopause
• if you're pregnant
• while you're growing if you're a child or young person
• if you're fasting (for example during Ramadan or for other religious reasons)
• if you change your daily routine, for example if you're doing shift work

It's a good idea to keep a record of the amount of insulin units you inject if possible.

Testing your blood glucose

Testing your blood glucose regularly will help you and your diabetes healthcare team know if you're taking the right dose for you. Your doctor or diabetes nurse will explain how to do this.

How to take it

Most people take short-acting insulin using an insulin pen or a pump. There are different types of pens and pumps so check the instructions for the type you're using.

If you use vials and syringes to inject instead of a pen, your diabetes nurse will show you how to do this.

Using an insulin pen

When you start taking insulin your diabetes nurse will show you how to use your pen to inject. Always follow the instructions for your pen.

Using an insulin pen does not usually hurt. The needles are very small as you only inject a small amount into the layer of fat just under your skin.

1. Wash your hands.
2. Attach a new needle to your pen every time you inject.
3. Remove any air from your pen by turning the dial to 2 units of insulin, pointing the pen up into the air and pressing the plunger until insulin starts to come out of the needle. If no insulin comes out then do this again.
4. Dial your dose of insulin by turning the dial on the pen to the correct number.
5. Choose a place to inject on your tummy, the sides of your thighs or your buttocks – make sure you use a different place each time.
6. Hold the pen at a right angle to your skin and push the needle into your skin.
7. Push the plunger in slowly, then hold the pen in place for 10 seconds to make sure you get the full dose.
8. Take the pen out of your skin, remove the used needle and put it in your sharps bin, then put the cap back on your pen.

It's important to vary the places you inject so that you're less likely to get fatty lumps under your skin (lipohypertrophy). Although these are usually harmless, they can mean that insulin is not always absorbed at the same speed when you inject into them. This can affect your blood glucose levels.

Using an insulin pump

Short-acting insulin can also be taken using an insulin pump, which you attach to your body.

Taking insulin safely

It's important to always take the right amount of insulin. To avoid making any mistakes with your insulin dose:

• make sure you know the name and strength of the insulin you use, and always check you have the right one
• make sure you know your usual dose and how to adjust it when you need to
• if you take 2 types of insulin, double check the type and dose each time you inject – you could keep the pens in separate places so that you do not mix them up
• get advice on your injection technique from your diabetes nurse
• if you're admitted to hospital, make sure the staff know about your insulin treatment

If you have a problem with your insulin pen

Insulin pens are designed to stand up to a lot of wear and tear. But they can sometimes become faulty, and this can affect your blood glucose levels.

If you're concerned that your pen is not reliably giving the right dose of insulin, contact your doctor or diabetes nurse for advice.

How long to take it for

If you have type 1 diabetes you'll need to take insulin for your whole life.

If you have type 2 diabetes you'll need to take insulin if other treatments for diabetes are not reducing your blood glucose enough. Once you start taking insulin it's likely that you'll need to take it for the rest of your life, provided it improves your blood glucose and you cope well with the treatment.

If you're taking insulin to treat gestational diabetes you can usually stop taking it once your baby is born, as the condition usually goes away after you give birth.

It's important to take insulin as recommended by your doctor or nurse. Speak to them if you have any problems with taking it.

When your blood glucose is well managed you're less likely to get the short-term symptoms of high blood glucose (hyperglycaemia) such as blurred vision, needing to pee more, tiredness and feeling very thirsty. You're also less likely to get serious long-term problems that can damage your heart, kidneys, eyes, nerves and feet.

Stopping insulin suddenly can lead to severe hyperglycaemia and a life-threatening condition called diabetic ketoacidosis.

If you have any concerns about your insulin treatment, talk to your diabetes specialist, doctor or diabetes nurse.

If you forget to take it

Taking too little insulin increases the risk of high blood sugar (hyperglycaemia) and long-term complications from diabetes.

If you forget to take your short-acting insulin before a meal, and you've already eaten, consider taking a slightly smaller dose or correction dose, or contact your doctor or diabetes nurse for advice.

Look out for any signs of high or low blood glucose levels, and check your blood glucose levels more often than usual. Contact your doctor or diabetes nurse if you're concerned.

Never take 2 doses to make up for a forgotten dose.

If you take too much

Taking too much insulin can make your blood sugar go too low, causing hypoglycaemia (a hypo). You might also have a hypo if you:

• miss or delay meals or have not had enough carbohydrates
• do lots of exercise without having the right amount of carbohydrates or reducing your insulin dose
• drink alcohol, especially after skipping a meal

Symptoms of a hypo

Symptoms of low blood sugar include:

• sweating
• trembling or shaking
• anxiety, confusion or difficulty concentrating
• fast heartbeat (palpitations)
• tingling lips
• changes to your vision such as blurred vision
• feeling dizzy
• feeling hungry
• paler than usual skin

It's also possible for your blood sugar to go too low while you're asleep. If this happens, you may wake up at night feeling sweaty and confused, or you may feel tired or have a headache in the morning. Speak to your diabetes team if you think you might be having hypos at night.

These symptoms happen when your blood glucose falls below 4mmol/L.

Treating a hypo

If you get hypo symptoms, follow the instructions you've been given to treat a hypo:

1. Have a sugary drink or snack, such as a small glass of fruit juice or sugary fizzy drink, 5 glucose or dextrose tablets, 4 large jelly babies, or 2 tubes of glucose gel.
2. Check your blood glucose after 10 to 15 minutes. If it's improved and you feel better, move on to step 3. If it's still low, have another sugary drink or snack, then check your blood glucose again after 10 minutes.
3. Once you blood glucose is back above 4mmol/L, eat a starchy carbohydrate that lasts longer in your blood, like a sandwich or some biscuits, or your next meal if it's due.
4. Once you feel better and your blood glucose is back under control, you can restart your insulin treatment.

Do not drive, cycle or use machinery if you've taken too much insulin, even if you do not have symptoms. If you have a hypo, do not drive for at least 45 minutes after you've recovered.

Try to make sure someone stays with you if you've taken too much insulin.

Find out more about side effects of short-acting insulin including severe hypos.