Testing background insulin when on multiple daily injections

Who should check their background insulin?

This leaflet is to guide people with insulin treated diabetes who use ‘pen’ devices, on how to check the effectiveness of their background insulin doses. This leaflet is not suitable for those using insulin pump therapy. Examples of twice daily background insulin include: Levemir and Humulin I. Examples of once daily background insulin include: Lantus, Abasaglar, Tresiba and Toujeo.

When is it useful to you check your background insulin?

If you think your insulin doses may not be right; it is always a good idea to check if your background insulin is correct first before changing your quick acting insulin/ratios.

The role of your background insulin is to keep glucose levels within the target range when you are not eating.

When to check your background doses:

• Consider a background insulin check every 12 months
• If there is a change in your routine
• A change in the type of insulin you are taking
• Weight gain/weight loss
• If you are experiencing more frequent hypoglycaemia/hyperglycaemia
• When you suspect your insulin dose is no longer right for you

When and how to check background insulin

When you take your background insulin twice a day (e.g. Levemir or Humulin I), the doses are assessed separately – overnight and during the day.

When you take your background insulin once a day (e.g. Lantus or Tresiba), the assessment is based mainly on your overnight glucose.

How to check your background insulin dose overnight

Do not start or continue a background test if:

• you have had a severe hypo within the last 24 hours
• you have had any hypos in the last 12 hours or have a hypo during the assessment
• your glucose is markedly above the target range (e.g. 17mmol/L or more), you have ketones present and you need to take a correction
• you feel unwell
• you have been more or less active than usual
• if you have had alcohol in the past 24 hours

The above may influence the results, therefore we would advise you delay the test to a more appropriate day.

Steps to check background insulin overnight

1. Have an early evening meal with your usual quick acting insulin, at least 4 hours before bed. Do not eat anything after your evening meal. Do not exercise or drink alcohol.
2. Take your background insulin as normal.
3. Measure glucose pre-bed. If glucose is 5 -11 mmol/l then continue the assessment
4. Wake up at 3 am to measure your glucose level. Only eat if glucose is below 5mmol/L
5. Do not use a quick acting insulin correction
6. Measure glucose on waking up. Compare the three readings.
7. If you are using CGM (e.g. Libre 2 Plus or Dexcom One+) you can use the overnight sensor trace rather than finger prick measurements.

You may need to repeat this a few times for a clear pattern. If you are injecting the right amount of background insulin then blood glucose levels should not rise or fall more than 1.5mmol/L.

Reviewing the results

• If your blood glucose increases more than 1.5mmol/L from bedtime to waking up, consider a 10% increase in your background insulin dose (the evening dose if you take background insulin twice a day).
• Consult your diabetes educator if your 3am blood glucose level is <5mmol/L but your waking glucose is consistently much higher.
• If your blood glucose decreases more than 1.5mmol/L from bedtime to waking up, consider a 10% decrease in your background insulin dose (the evening dose if you take background insulin twice a day).
• If you have made a change to your evening background insulin dose, consider a follow up background insulin check overnight.
• If you increase your evening background insulin dose (or any increase in a once daily background insulin), always do a 3am glucose measurement to make sure you are not experiencing low glucoses overnight. Your glucose level should be greater than 5 mmol/L at 3am.
• If your blood glucose increases more than 1.5mmol/L from bedtime to waking up, consider a 10% increase in your background insulin dose (the evening dose if you take background insulin twice a day).
• Consult your diabetes educator if your 3am blood glucose level is <5mmol/L but your waking glucose is consistently much higher.
• If your blood glucose decreases more than 1.5mmol/L from bedtime to waking up, consider a 10% decrease in your background insulin dose (the evening dose if you take background insulin twice a day).
• If you have made a change to your evening background insulin dose, consider a follow up background insulin check overnight.
• If you increase your evening background insulin dose (or any increase in a once daily background insulin), always do a 3am glucose measurement to make sure you are not experiencing low glucoses overnight. Your glucose level should be greater than 5 mmol/L at 3am.

How to check your background insulin dose during the day

When checking the background insulin dose during the day, it is important that there are no quick acting insulin or carbohydrates taken during the assessment period as this will affect the results. This means that you will need to skip (or delay) the meal that you would usually eat over the time of the assessment. Avoid exercise and alcohol the night before the background assessment.

Do not start a background test if:

• you have had a severe hypo within the last 24 hours
• you have had any hypos in the last 12 hours or have a hypo during the assessment
• your glucose is markedly above the target range (e.g. 17mmol/L or more), you have ketones present and you need to take a correction
• you feel unwell
• you have been more or less active than usual
• if you have had alcohol in the past 24 hours

The above may influence the results, therefore we would advise you delay the test to a more appropriate day.

Steps to check background insulin during the day

1. Take your morning background insulin as normal.
2. Have your usual breakfast with quick acting insulin, and a correction if necessary. Have nothing else to eat after this. Sugar free fluids/water is fine.
3. Measure your glucose before lunch (ensure this is at least 4 hrs after breakfast).
4. Only continue the assessment if glucose is between 4 -11 mmol/L.
5. Omit lunch altogether (this is the most accurate background assessment).
6. Measure your glucose every 2 hours in the afternoon, or use your sensor glucose reading.
7. Only eat if glucose is below 4 mmol/L
8. Do not use a quick acting insulin correction
9. Do not exercise or drink alcohol for the duration of the assessment.
10. Measure glucose before your evening meal and have your usual meal with quick acting insulin.
11. Take your evening dose of background insulin as normal

Reviewing the results

If you would like support to interpret your background insulin test results, please contact your diabetes educator by email or phone.

Contacts/further information

• Diabetes Specialist Nurses: 01223 348790
• Diabetes Specialist Dietitians: 01223 348769
• MyChart message: Diabetes Educators
  Email diabetes educators

References/sources of evidence

DAFNE – Dose Adjustment For Normal Eating

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