Prevent Low Blood Sugars

For better blood sugars and fewer lows, test often and review your readings once a week for patterns of lows or highs (or both). Identify problems first, then consider their causes and how to correct them. Make one change at a time and correct lows first. If you need any advice at all about how to correct a problem, be sure to call your physician or nurse educator right away. Do not let control problems linger as they usually turn into larger problems.

When trying to prevent low blood sugars, it helps to understand their most common causes. The table below outlines the most triggers for lows. If your are currently experiencing either frequent or severe reactions, look carefully at this list to see what might be causing them. Once you identify a cause, decide upon a correction. Remember: when low blood sugars are frequent or severe, it is almost always necessary to reduce current insulin doses. If lows blood sugars happen infrequently, try to identify the trigger so you can make adjustments when you encounter that situation again.

Common Triggers and Corrections
Cause Correction
too much insulin less insulin
skipped meals eat regularly or reduce fast-acting insulin for that meal
light meal less insulin or more eating
lost weight less insulin or more eating
more active less insulin or more eating
vacation less insulin or more eating

How to Prevent Lows:

  • Eat the meals and snacks for which you’ve taken insulin.
  • Test your blood sugars often.
  • Count the carbohydrates in each meal. Match your pre-meal Humalog, NovoLog, or Regular to the amount of carbohydrate and to the current blood sugar.
  • Learn to use your test results to adjust your insulin and food. For example, if low blood sugars happen in the afternoon, an afternoon snack or less insulin in the morning or at lunch can help.
  • Test before, during, and after exercise. Long periods of exercise can cause low blood sugars up to 24 to 36 hours later.
  • Be alert for a change in your daily routine, such as travel, vacation, weight loss, etc.
  • Be careful with alcohol. Inebriation and hypoglycemia have a lot in common.
  • Always check blood sugars before driving and during long drives

Using Insulin To Prevent Lows

  • Frequent or severe insulin reactions do not happen when blood sugars are tested often and insulin doses have been correctly matched to meals and lifestyle.
  • A varied lifestyle with set doses of insulin spells disaster. Control is better when you use small doses of insulin frequently and match them to your lifestyle.
  • “Brittle” diabetes is simply insulin given in the wrong amounts or at the wrong time.
  • Humalog or NovoLog controls the blood sugar over the first 4 hours and Regular controls the first 6 hours after injection. Lente or NPH controls the blood sugar largely at 4 to 12 hrs after the injection. Ultralente’s timing gives it the greatest effect at 8 to 18 hours, while the new Lantus has much less peaking action but its activity is evenly spread over 4 to 24 hours.
  • Understand insulin timing to correct patterns of highs and lows.
  • Everyone needs to adjust insulin doses occasionally. Know when to contact your physician for these changes.

How To Prevent Night Lows

The lowest blood sugar of the day usually occurs around 2 a.m. In an early study of people with Type 1 diabetes using Regular and NPH, researchers found they averaged one low blood sugar every four nights. Fortunately, today’s new analog insulins have reduced the frequency of lows, especially at night.

Lows occur in the middle of the night because the body is most sensitive to insulin between midnight and 3 a.m. Around 3 a.m., the liver starts to increase glucose production, causing the blood sugar to rise toward breakfast.
If you suspect you may be having night lows, test at 2 a.m. for a few nights. If your reading is low at that time, lower your evening basal dose and test until you are sure your blood sugar drops no more than 30 mg/dl (1.7 mmol) at any point during the night.

You might also consider another approach if your morning basal dose is much larger than your evening dose. For instance, if you take 40 units of Lente before breakfast, but only 4 units at bedtime, the morning dose is likely the one that needs to come down. Try reducing the morning to 36 units first and later increase the bedtime dose to 6 units if the morning reading becomes high.

If you are still using Regular insulin, switch to Humalog or Novolog to help avoid lows. If you use Lente, NPH, or Ultralente, consider switching to Lantus insulin. Recent unpublished research in a large group of people with Type 1 diabetes by Dr. Satish Garg at the University of Colorado shows Lantus helps to lower the risk of hypoglycemia.

Prolonged exercise or activity can cause the blood sugar to fall for 24 to 36 hours afterward. After a day of increased exercise or activity, it is wise to reduce the carb bolus for dinner and the evening basal dose as well. Extra free carbs at bedtime that you do not balance with a bolus are also wise.

Covering high bedtime blood sugars with too large a correction bolus is another common trigger for night lows. Try bringing down bedtime highs with half your normal correction dose.

Prevent Follow-up Low Blood Sugars

One low blood sugar increases the risk for another. Researchers in Virginia found that the chance of having a second low after one initial reaction increased by 46 percent over the next 24 hours, 24 percent on the second day, and 12 percent on the third day after the original hypoglycemic event.35 Enhanced sensitivity to insulin following the first low blood sugar contributes to this increased risk.

Not only is the risk of a second low greater, but symptoms during the second one are milder and harder to recognize. After stress hormones are released during the first low blood sugar, the body’s stores are reduced for the next two to three days, causing a reduction in warning symptoms.

Do not take chances. Take steps to keep your blood sugar higher for the next 24 hours after a low by eating free (uncovered) carbs or lowering your carb boluses.

Adapted from Using Insulin © 2003. Walsh, Roberts, Varma, Bailey.

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