high fasting blood sugar

Q: I’ve had diabetes for 15 years and struggle with high fasting blood sugar. They are usually between 130 and 180. I’m on oral medications. I’ve tried everything to get it down and have not had any success so far.

Getting fasting blood sugar under control can be especially challenging! High fasting blood glucose (BG) numbers tend to lead to overall higher BG levels throughout the day, so it’s important to try to figure out and address the root cause. 

But first, what goal blood sugar number are we targeting for the morning fasting time? In general, glucose values between 80-120 are desired. A goal of 100 is easy to remember. There could be reasons that a more strict or lenient goal would be set, but most people with diabetes try to target 100. 

Let’s look at some possible contributing factors to high morning fasting numbers.

Dawn phenomenon

This is a natural rise in BG that occurs between 4 – 8 am due to hormonal changes in the body. Cortisol and growth hormone are secreted around this time and raise BG. These hormones are basically signaling your body to give you fuel (blood sugar) to get your day started. For those without diabetes, the body produces enough insulin to overcome these hormonal swings and the BG doesn’t change much. But with diabetes, the natural insulin response is impaired, so the BG rise due to these hormones can be substantial.


Fix it:

  • If you are treated with insulin, your healthcare provider can increase the insulin dose or adjust the timing to bring your glucose down.  If the problem is related to insulin wearing off, the once-daily dose could be split into two, or the once daily dose could be moved closer to bedtime so that it covers the 4-8 am rise.
  • For those on oral meds only, it is more challenging to affect the Dawn phenomenon, but changing up the timing of medications could help.
  • Another option is to experiment with varying the number of carbs eaten at dinner or for a bedtime snack. Sometimes a lower carb snack is needed, but other people may need a few more carbs to prevent their liver from sending out too much glucose. Frequent monitoring would help distinguish whether more or fewer carbs are needed. 


Somogyi effect

The Somogyi effect (named for the researcher who discovered it) is your body’s response to a low BG that happens while sleeping. The low could be due to too much insulin, not enough food, too much alcohol or other reasons. When your body senses the low, it triggers a hormone called glucagon – which then tells your liver to release glucose to treat the low. This can send your glucose into a rebound high, which is what you see when you wake up.


Fix it:

  • To identify whether you are experiencing a Somogyi effect, you will need to check a few BG readings around 3 am to see if you are low (<70 mg/dL) at that time. If so, it is likely the rebound release of glucose that is causing your high numbers.  If this is happening, you may need to add a few carbs to a bedtime snack or decrease the amount of insulin taken late in the day to prevent the overnight low from happening.


Insulin wearing off

If you are taking a long-acting insulin, the general assumption is that it will work for 24 hours, but that is not always true.  Levemir is shorter acting than Lantus. Basaglar may not hold as long as Lantus either. Tresiba is longer acting than the other basal insulins.  We also know that the same dose of insulin can have a longer or shorter duration of action in an individual. There are plenty of scenarios to explain the variation. 


Fix it:

  • The only way to know if insulin is wearing off is by checking glucose more frequently for a short period of time. A continuous glucose monitor (CGM) would also be a great way to detect this.


Insulin resistance


Insulin resistance can contribute to high morning fasting blood sugar in a couple of ways. Insulin is the messenger that tells your cells to open up and let the glucose in to be used as fuel. When your body isn’t sensitive or responsive to the insulin it makes, muscle and fat cells are unable to use glucose effectively and it builds up in the bloodstream causing the symptoms of hyperglycemia.


In addition to that, the liver is your body’s storage place for glucose. Insulin also has the job of telling the liver to stop sending glucose into the bloodstream. But in type 2 diabetes, insulin resistance causes the liver to ignore the signal from insulin and dumps more glucose than is needed. This can occur all day long, but it happens more frequently at night, leading or high morning BG.


Fix it:

  • How do you treat insulin resistance? The full answer is lengthy, but the short answer is decreased carb intake, weight loss, and more physical activity all make a difference.
  • Medications such as metformin and pioglitazone can decrease insulin resistance.


Carb overload


Simply eating too many carbs at dinner or bedtime can contribute to high morning fasting BG numbers. Your tolerance to a carb load is not the same as anyone else, so learning how carbs affect you is valuable information.


Fix it:

  • Depending on your evening blood sugar, skipping the bedtime snack might help. Adding protein or fat to your evening meal or bedtime snack may also reduce the spike.
  • Light evening exercise like an after-dinner walk can bring down post-meal glucose.
  • Learning to eat to your meter can help you identify which foods spike your BG and which ones don’t.


So where’s the encouraging news in all of this? You are the captain of your ship. You can do self-experimentation to figure out what is causing your high morning BG. Approach it as if you’re doing detective work. Investigate one cause, then another until you find out what’s happening in your body. Diabetes doesn’t act the same in everyone, so you’ll need to always take an active role in being the best student of yourself. That can be an overwhelming and exhausting job, but it will pay off! Your health is worth the investment of time and energy!

What has made the difference in controlling your morning fasting blood sugars?  Tell us in the comments.

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