Tuesday, May 11, 2010

Understanding Fasting Blood Sugar

Among the most common questions people have about Type 2 diabetes is this: how can they lower their fasting blood sugar?

To answer this question in a way that will help you lower your blood sugar we are going to have to first explain why doctors measure fasting blood sugar and what it does--and does not--tell us about our blood sugar health.

WHAT IS FASTING BLOOD SUGAR?

Traditionally, fasting blood sugar is the value you get when you test your blood sugar after an 8 hour long fast--which is usually immediately upon waking. In a normal person this fasting blood sugar would also be the "baseline" blood sugar--the level to which blood sugar returns a few hours after every meal all day long.

However, for reasons we will discuss later on, this is often NOT the case for people with Type 2 diabetes, whose morning blood sugars may be much higher than the baseline level they achieve after meals for the rest of the day.

Doctors have for decades relied on the FPG (fasting plasma glucose) test which measures fasting blood sugar to diagnose diabetes. The reason for this is NOT that FPG test results predict diabetic complications. They don't. Post-meal blood sugar tests are a much better indicator of whether a person will get the classic diabetic complications, and the A1c test is a better indicator of potential heart disease.

But the FPG test is cheap and easy to administer, hence its popularity.

The value most of us would find much more helpful in assessing our health is not fasting blood sugar but something else: the number of hours a day our blood sugar spends elevated over the level known to cause complications, which is roughly 140 mg/dl (7.7 mmol/L).

A person can wake up with a FPG of 130 mg/dl (7.2 mmol/L), but if it drops after breakfast and most hours of the day are spent with blood sugars that remain under 120 mg/dl, the person can expect years of complication-free living.

In contrast, a person may wake with a normal FPG of 98 mg/dl (5.4 mmol/L) but end up spending the next 14 hours with blood sugars well over 170 mg/dl (9.4 mmol/L). That person is seriously at risk for heart disease, diabetic nerve damage, kidney damage, and retina damage.

So when you assess your own fasting blood sugar, the question you want to ask is this: How many hours a day am I spending with my blood sugar in the range that causes complications? Not, necessarily, how can I lower my fasting blood sugar?

Obviously, if your fasting blood sugar is over 140 mg/dl (7.7 mmol/L) and goes up after each meal, you are going to be spending many hours a day in the danger zone and lowering your fasting blood sugar does become a huge issue. Fortunately, it is also one that can be solved.

WHAT RAISES FASTING BLOOD SUGAR?

Several independent factors can raise fasting blood sugar, and if you have a problem with it, the reason for your problem may NOT be the same as the reason for another person's even if they get the identical blood test results that you get.

Here are common reasons for high fasting blood sugar.

1. High post meal blood sugars. Your beta cells can only make so much insulin. If you elevate your blood sugars severely by eating more carbohydrate than your body can handle, your body will spend the whole night using what insulin it can manufacture to mop up the glucose that is still circulating thanks to those high carb meals.

Many people with diabetes cannot handle more than 12-20 grams of carbohydrate at a single meal, no matter what you might have been told by doctors or dietitians. Many of us will find that if we drop our carbohydrate intake dramatically, our fasting blood sugar plummets equally dramatically. It may take as little as two weeks of restricted carbohydrate intake to see fasting blood sugars revert to normal.

You can use this technique to lower your fasting blood sugar. It has worked for literally thousands of people:

How to Get Your Blood Sugar Under Control

2. Damaged Basal Insulin Secretion. The body secretes insulin in two different physiological processes which are described on this page: How Blood Sugar Control Works--And How It Stops Working. I urge you to read this page because mastering the concepts it explains will greatly help you understand and manage your diabetes.

Basal insulin secretion takes place throughout the day without reference to what you eat. Tiny amounts of insulin are squirted into the blood stream in small pulses every few minutes. However, sometimes things go wrong with the factors that control basal secretion. If that happens, your body may still be able to secrete insulin in response to meal time rises in glucose, but you lose the ability to secrete those tiny pulsing bursts. This can cause a rise in fasting glucose that can not be corrected with dietary changes. If you have this problem, you might need a basal insulin--a slow acting insulin that mimics the effect of natural basal secretion.

Basal failure is relatively rare, but when it happens you often find people with high fasting blood sugars whose blood sugar normalizes as soon as they eat and stays normal until they have metabolized their last meal. There are also genetic forms of diabetes (GCK mutations) that will cause elevated fasting glucose, however, this will be a lifelong problem, not one that comes on with age.

3. Dawn Phenomenon. If your blood sugar is highest first thing in the morning, and normalizes after you eat or exercise and stays normal hours after dinner, you may have a disturbance of regulatory hormones that is called "dawn phenomenon."

Our bodies prepare for waking up by secreting stimulating hormones shortly before dawn. These increase our insulin resistance in order to raise blood sugar a small amount. If we were animals who had to go hunt for our first meal, that excess glucose would be useful. Since were are people with refrigerators, it is less so.

Everyone experiences this early morning hormone burst, but in people with diabetes it can become highly exaggerated. In some people it is resistant to any treatment, but once the person goes about their day and eats, the blood sugars become more controllable.

If you have dawn phenomenon that doesn't respond to various lowering techniques, don't panic. As long as you are spending most of the day with your blood sugars at a safe level (Always under 140 mg/dl and under 120 mg/dl as much as possible) you'll be fine.

4. Too Much Injected Insulin or Oral Insulin-Provoking Drug. This is counter-intuitive, but common. If you are using a basal insulin (Lantus or Levemir) there is a temptation to use a lot of it to try to lower post meal blood sugars. Your sugars will be pretty good as long as you keep eating carbs, but once you stop eating at night, the insulin keeps being absorbed into your blood stream and by 3 AM it is quite common to hypo.

However, many of us as soon as we hypo slightly, experience a burst of counterregulatory hormone intended to push the blood sugar back up to normal so by the time you wake your blood sugar is high, not low. You can tell if you have had a counterregulatory burst because it will often wake you up at 3 AM with a jolt. Your pulse will be fast and your blood pressure may be elevated too. If you measure your blood sugar it won't be low, because as soon as you get that jolt, your blood sugar will surge. That's what the jolt is meant to do.

If you are waking at 3 or 4 AM and end up with high fasting blood sugars, cutting back on your Lantus or Levemir may solve the problem. Lantus and Levemir are NOT meant to cover the carbohydrates you eat at meals, only to lower your baseline blood sugars. If you need insulin to control meals, you need to ask your doctor for fast acting insulin and the diabetes education it requires to learn how to use it correctly.

Glipizide and Amaryl (glimepiride) can also cause this problem as they cause long lasting insulin secretion in people who are sensitive to them.

5. Too Much Blood Pressure Medication. Too much blood pressure medication will also cause an early morning counterregulatory attack because if your blood pressure drops too low, you will get a burst of epinephrine and other hormones meant to keep you alive. It will raise both blood pressure and blood sugar.

I experienced this myself and since posting about it on my blog have received emails from others who experienced this same phenomenon. It is most likely if your blood pressure medication is giving you low normal readings during the day--90/60 for example, or if you experience postural hypotension attacks where you black out when you bend over.

USEFUL TECHNIQUES FOR LOWERING FASTING BLOOD SUGAR

Here are some of the things people report helped them. They are worth a try.

1. Cut way back on your meal-time carbohydrate intake.

2. Drink a glass of wine with dinner or before bedtime. One is enough. The alcohol can inhibit the liver from dumping glucose.

3. Eat a protein snack before bedtime.

4. Change the time of day when you take your medications. Metformin ER taken at bedtime will have a stronger impact on fasting blood sugar than the same pill taken in the morning. However, you may see higher post meal values if you change the timing. Remember your goal is maximum hours of lower blood sugar, not one low reading in the morning.

5. Split Lantus or Levemir doses so you take half in the morning and half in the evening. Lantus does not last 24 hours in many people, especially when taken in small doses (12-30 units) so if you take it in the morning it may be gone by 3 AM. Splitting the dose may give you better coverage. Discuss this with your doctor before you make changes, especially if you haven't been taught how to adjust your insulin doses. DO NOT MODIFY YOUR INSULIN DOSES IF YOU DON'T UNDERSTAND HOW THEY WERE SET!

6. Metformin. If you aren't taking metformin, ask your doctor about it. It is the most appropriate drug for controlling fasting blood sugars because it can sometimes block the liver dumping that raises blood sugar in response to dawn phenomenon hormones.

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