Blood Sugar Challenges in Insulin Therapy

Insulin therapy is all about balance and fine-tuning. It’s normal to experience a challenge or two, especially when you begin the regimen.

Low Blood Glucose at a Particular Time of Day

To combat this problem, keep track of when the low levels are occurring, and consider which insulin is having its peak action at that time of day. Your doctor may suggest that you reduce that insulin dose by one or two units. For example,

  • If the low blood glucose consistently occurs before dinner, your doctor may reduce the morning or lunchtime dose of NPH insulin by one or two units.
  • If the low blood glucose event is more frequent in the morning before breakfast, your doctor may reduce the evening dose of NPH or Lantus® by one or two units.

    It may take a day or two for your insulin-balancing hormones to adjust to the change in dose. As a result, your blood glucose may be high for a few days after you reduce the insulin dose. Be patient and wait several days for the hormones to adjust.

High Blood Glucose in the Morning

There are several reasons why your blood glucose might be higher in the morning than it was at bedtime.

  • Growth hormone release (Dawn Phenomenon)
    The levels of growth hormone may begin to rise in the early morning hours. Growth hormone stimulates the liver to release glucose into the bloodstream. This is sometimes called the “Dawn Phenomenon”.

  • Bedtime insulin needs adjusting

    If you take NPH at bedtime and the dose is too low, then by 6:00 a.m. the insulin will be past its peak effect and you may experience a rise in blood glucose. Your doctor may tell you to increase the bedtime dose.

    If you take Levemir® at bedtime, but you take it late (for example, at 11:00 p.m.) then it will just be entering its peak effect period eight hours later, at 7:00 a.m. As a result, you may wake up with high blood glucose. Ask your doctor if you can take your Levemir injection earlier, for example at 7:00 pm, so that its peak effect will occur between 3:00 and 11:00 in the morning. Your doctor may also decide to adjust your dose.
  • Rebound Hyperglycemia

    If your blood sugar falls rapidly during the night, your liver may be triggered into releasing glucose into the bloodstream. Sometimes when this happens, too much glucose is released, and the result is called “Rebound Hyperglycemia.”

    You can tell whether you are experiencing the Dawn Phenomenon or Rebound Hyperglycemia by checking your blood glucose around 3:00 a.m. If the glucose level is high, you are probably experiencing the Dawn Phenomenon. If the glucose reading is low, then rebound hyperglycemia may be the cause of your high morning test results. You should discuss this with your doctor.

Download a blood glucose logbook

Know which insulin dose to change

If you often have high blood glucose at a specific time of day, think about which insulin is having its peak effect at that time of day. That insulin may need to be increased by 1 or 2 units. For example,

  • If your blood glucose is high before lunch, then your breakfast rapid or short-acting insulin dose may need to be increased.
  • If the glucose reading is high before the evening meal, then your morning basal insulin dose or your lunchtime bolus dose may need to be increased. 
  • If your glucose level is high at bedtime, your doctor may consider raising your dinnertime rapid or short-acting insulin dose.




The BD Diabetes Learning Center describes the causes of diabetes, its symptoms, and diabetes complications such as retinopathy and neuropathy. This site contains detailed information about blood glucose monitoring, insulin injection and safe sharps disposal. Interactive quizzes, educational literature downloads and animated demonstrations help to teach diabetes care skills.

Important Note: The content of this website is not intended to be a substitute for professional medical advice, diagnosis or treatment. Do not disregard your doctor's advice or delay in seeking it because of something you have read in this website.

Unless otherwise noted, BD, BD logo and all other trademarks are property of Becton Dickinson and Company. © 2017 BD