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New research is shedding light on one of the most distressing problems faced by a group of people who have diabetes (as well as their family, friends and co-workers). The problem, called hypoglycemia unawareness (HU), occurs when a person becomes incapable of dealing with his own low blood sugars. If unnoticed and untreated, HU can create serious problems, including grand mal seizures. If you've ever witnessed seizure activity or bizarre behavior in someone, you have some idea of the impact of HU and its danger.
The person with HU is unable to recognize that she is having a low blood sugar and therefore cannot think clearly enough to correct it. A critical imbalance occurs in HU: thinking ability is lost before warning symptoms are severe enough for the person to recognize them. By the time symptoms reach a level most people would recognize, the mind of the person with HU is unable to recognize serious shaking, nervousness, and sweating. That this could occur during sleep is not surprising, but that it would occur while someone is awake is disturbing.
Risks of both hypoglycemia and HU increase as a person's average blood sugar is brought from high readings closer to normal. In the DCCT study, 55% of HU episodes occurred during sleep and they were three times as common in the intensively controlled group.
The mind usually recognizes reaction symptoms, and this allows a person to deal with the dropping blood sugar. But if the blood sugar drop is rapid, if someone has had diabetes for many years, if stress or depression are present, or if self-care is a low priority for any reason, the mind is less likely to recognize a reaction before it becomes truly severe. Reaction symptoms become less obvious after many years of diabetes because less epinephrine and glucagon are released. These stress hormones create the symptoms which make a reaction obvious to the person having it.
Drinking alcohol is also a risk factor. Alcohol contributes to HU in three ways: the mind is less capable of recognizing what's happening, the liver is blocked from creating the glucose needed, and the release of free fatty acids (the backup to glucose for fuel) is also blocked. (A. Avogaro and others: Diabetes 42: 1626-1634, 1993)
Researchers have discovered several ways to avoid HU. Keeping blood sugars slightly high, with better matching of insulin doses to diet and exercise is one way. Other options are keeping the warning signals active and keeping brain cells operating under the duress of hypoglycemia.
Significant loss of warning signals occurs if someone has had a recent low blood sugar. Dr. Thiemo Veneman and other researchers demonstrated this principle in an article published in the November, 1993, issue of Diabetes. Dr. Veneman and his group got 10 people who did NOT have diabetes to spend a day at the hospital on two occasions.
While they slept, the researchers used insulin to lower their blood sugars to between 40 and 45 mg/dl for 2 hours in the middle of the night (No, they didn't wake up! Most of us don't wake up during nighttime reactions. Memory serves us only for the reactions that wake us up). Five people experienced a nighttime low on the first visit and the other five on the second visit. Then, after waking in the morning, all were given insulin to lower their blood sugars to see when they would recognize they were getting low.
Dr. Veneman found that after sleeping through a reaction at night, people had far more trouble recognizing a low blood sugar the following day. Low blood sugar symptoms come from the release of counter-regulatory hormones. These researchers found that stress hormones like epinephrine and glucagon were released more slowly and in smaller concentrations after a nighttime reaction (actually after any reaction at all). In other words, a recent low makes it likely that you'll fail to recognize the second low.
This is unfortunate because one low blood sugar increases the risk of actually having another low blood sugar. Daniel Cox, PhD, and other researchers reported at the 1993 American Diabetes Association meeting that the chances for having a second insulin reaction following any reaction are greatly increased: 46% in the next 24 hours, 24% on the second day, 12% on the third day and only 2% on the fifth day after the original reaction.
In a major contribution to controlling HU, Dr. Carmine Fanelli and others (Diabetes 42: 1683-1689, 1993) worked with people who had had their diabetes for seven years or less, but who suffered from HU. The researchers and their subjects worked to reduce the frequency of insulin reactions by aiming for moderately higher premeal blood sugars (140 mg/dl). Frequency of hypoglycemia dropped from once every other day to once every 22 days.
By raising premeal blood sugars, the researchers found that people who previously had had trouble recognizing their reactions were now able to do so. The counter-regulatory hormone response in these subjects returned to values that were nearly normal. These researchers demonstrated for the first time that HU is reversible.
Obviously, keeping one's blood sugar target slightly higher, avoiding low blood sugars, and being especially careful following a first reaction are the best ways to prevent HU. The most important tool in treating HU is matching insulin to diet and lifestyle. Someone who does this is less likely to suffer from reactions and HU. For those with a physically active lifestyle, insulin adjustments may need to be made daily. This is the appeal of multiple injections and insulin pumps: being able to adapt to the variability of daily life, while encountering fewer and less severe insulin reactions.
Often other people can help someone who suffers from HU avoid a severe reaction if they recognize what's happening and take appropriate action. If someone with diabetes who takes insulin begins to act funny over a short period of time (usually 10 to 30 minutes), an insulin reaction is very likely and HU must be considered.
A person's actions may be bizarre during HU, with irrationality, irritability, running away, or insistence that he "feels fine" in the midst of behavior that is obviously unusual to others. Thinking is limited, fight or flight hormone levels are high, and an emotional reaction is likely. The person who wants to help in this situation should gently coax and encourage the person with HU to eat or drink fast-acting carbohydrate. Making demands upon or confronting an individual who already has high stress hormone levels isn't wise.
Plans to avoid HU will work only if the person who is having frequent lows or episodes of HU recognizes there is a problem to be dealt with. He or she must agree ahead of time to work with a spouse or co-worker in testing the blood sugar or eating if the support person requests this. And keep George R. from January's column in mind. He seemed able to keep his brain cells more active in the face of severe low blood sugars with antioxidants.
Whenever insulin reactions are occurring frequently or whenever an episode of HU occurs, insulin doses must be lowered immediately. Discuss any situation like this with your physician that day. Avoiding frequent insulin reactions, including nighttime reactions, is also a very good policy in avoiding HU. An occasional 2 a.m. blood test can do wonders in preventing HU due to unrecognized nighttime reactions.
Reading test for brain damage (if this makes sense, you're in trouble...):
"People tell me one thing and out the other. I feel as much like I did yesterday as I did today. I never liked room temperature. My throat is closer than it seems.... I don't like any of my loved ones."
[Editor's Note: Another possible cause of hypoglycemic unawareness is autonomic neuropathy. To find out more about neuropathy, contact your physician.]
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