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Basal rate testing is designed to help check how well the basal (background) insulin is working. If the basal insulin is working effectively, blood glucose levels should remain stable and in target
(4–7 mmol) during periods of time when you are not eating, such as overnight, or when there are no carbohydrates on board to affect the blood glucose level. Testing basal rates involves having
carbohydrate-free meals and two-hourly testing during the chosen time block. If basal rates are correct blood glucose levels will remain within the target range of 4–7 mmol If levels are not stable
during these times we can help you to make appropriate adjustments. It is quite hard work to do this, however, we believe that it provides real benefits and it is recommended that this is done prior to each clinic visit or as required.
It is useful to check basal rates at all times including overnight. Most people will choose to have one carbohydrate-free meal per day to check if basal rates need adjusting rather than do a carbohydrate free day!
When to do basal rate testing:
It is best to choose days that are “normal days” i.e. not days when there has been more activity or exercise than usual or parties or social events. Ensure blood glucose is in target before the beginning of the testing period – ideally between 5 -7mmol/l and definitely less than 14mmol/l. Do not start if a low blood glucose level has been experienced up to 4 hours previously.
Rules for basal rate testing:
• Ensure the last meal containing carbohydrate was 4 hours prior to the testing time block – 4 hours allows all your active bolus insulin to have finished working and for food to be digested
• Avoid low glycaemic index or high fat meals such as pizza, curries or pastas as your last meal as they can continue to affect your blood glucose levels for several hours
• DO NOT eat any carbohydrate during the testing periods. Carbohydrate-free meals such as plain meat, fish, eggs or cheese with mushrooms and green vegetables i.e. spinach, broccoli (some green vegetables if eaten in larger quantities will contain carbohydrate) is fine. Salads may be eaten i.e. lettuce, cucumber and celery but avoiding tomatoes as these contain carbohydrate.
• Avoid fish or meat with pastry or breadcrumbs/batter
• You can drink as much as you like but ensure drinks do not contain carbohydrate
Basal Rate Testing for Insulin Pump Users
• Test blood glucose levels every two hours during the testing period (until the next meal) and record results.
Rules regarding levels during this period of testing
• Blood glucose levels above target and below 14 mmol/l – do not correct the blood glucose and continue with the basal rate testing – this will allow you to see how the basal insulin changes the blood glucose level.
• Blood glucose is 14 mmol/l or above – check for ketones. If ketones are less than 0.6 mmol/l, take no action and continue with the basal rate testing. If ketones are greater than 0.6 mmol/l,
correct the blood glucose level and treat according to treatment of hyperglycaemia for insulin pump users. Abandon test.
• Blood glucose level is less than 4.0 mmol/l – treat the hypo in the usual way and abandon the test. If at any point during the testing period a hypo occurs, you need to stop and treat the low blood glucose and abandon the test for that day.