Understanding Glucose and A1C Numbers

Almost All Annual Physicals Measure Fasting Glucose. A1c Should Always Be Included But Is Not. More Things Should Be Measured, But Here Are The Health Implications of These Two.glucose-a1c-molecules

Glucose is the most common “simple” sugar. Fructose is the second most common one. Together they account for the bulk of sugar you consume.

All the starch you eat is converted directly to glucose, and gets quickly into your bloodstream. Carbohydrates from vegetables do as well, but more slowly. Table sugar and fruit are about half glucose and half fructose. If these two are combined it is called sucrose. It will be split into the two before it gets very far into your digestive tract. Fructose is stored by the liver and converted to glucose. So for all practical purposes all starch, all sugars, end up as glucose.

Glucose is energy. It is one of the four types of energy the body’s cells can run on, the other three being fat, protein, and ketones. Protein can be used for structural uses and won’t be burned for energy if other sources are available. Fat is the preferred fuel for most cells, but not the brain. The brain cannot run on most types of circulating fat. The brain has an extra layer of protection against various toxins and creatures like bacteria and viruses. It accomplishes this protection by invoking a fine mesh called the Blood Brain Barrier. Glucose can make it through, but most fats cannot . (Small fats like butter fat – butyric acid – can. Cream in your coffee? Yum!) Because of this, the body tries to maintain a circulating level of glucose equal to around 80 mg/ml. (Outside America 4.4 mmol/l). If there is more glucose, then the body will get rid of it by first storing it in the liver, then forcing the muscle to use it, then storing it as fat. If the glucose is low, the liver will dump some into the bloodstream from the supply it stored earlier. The liver can also make some sugar from fat.

The Annual Physical

The annual physical normally measures the fasting glucose; sometimes they add A1c. They then go on to confuse the average glucose measurement by calling it A1C or Hemoglobin A1C. It gets this strange name because it is an indirect measurement. However, a lot of the other blood measurements are indirect as well, such as LDL cholesterol, and they call those ones by the name we wish we could measure. But A1C is given as a percentage. Below 5% is great, and Above 5.7% is pre-diabetic. But what does this mean exactly? Glucose, being a sugar, is sticky. Some of it sticks to hemoglobin, the red stuff in red blood cells. The higher the average glucose, the more that sticks. So they look at the hemoglobin and determine how much glucose is stuck to it. 5% means 5% of the hemoglobin molecules had a glucose molecule stuck to them. This can be directly related to average glucose. Average glucose would be the number you would get if you measured glucose every 5 minutes and averaged. It should be low (80 mg/dl) a few hours after a meal, but usually shoots a lot higher right after a meal. So here’s a little chart to convert the percentage A1C to average glucose.

A1C Avg Glucose in mg/dl Avg Glucose in mmol
4.9 (good) 94 5.2
5.0 97 5.4
5.1 100 5.55
5.2 (good) 103 5.7
5.3 (marginal) 106 5.85
5.4 108 6.0
5.5 111 6.15
5.6 (marginal) 114 6.3
5.7 (serious) 117 6.45
5.8 120 6.7
5.9 123 6.85
6.0 126 7.0
6.1 (serious) 129 7.15

Most doctors will say A1C of 5.5%, meaning 111 mg/dl or lower is OK. We would say “don’t skate on thin ice.” Below 5.2% (103 mg/dl) is safe, and below 5% (96 mg/dl) is desirable. Likewise, many doctors say a fasting glucose below 100 mg/dl is OK. Not so. Try to get it below 80 md/dl.

What’s the point?

It’s not just adult onset diabetes. Glucose seems to be a major player in most degenerative disease. The plaque that gums up arteries, causing atherosclerosis, typically has some glucose components in it. Excess sugar raises triglycerides, a major heart risk factor. Excess glucose leads directly to insulin resistance, weight gain, and if carried far enough, adult onset diabetes. The brain damage seen in Alzheimer’s tends to have glucose products present. Finally, glucose is a cancer promoter. Cancer cells preferentially – strong bias – survive on glucose, and they need a lot of it.

What’s the solution?

Fasting glucose and A1C are mainly diet-driven numbers. Cutting down on starch and sugar will (immediately) lower them. For many, including both of your blog writers, that cut will have to be 100%. We just don’t process starch and sugar well, and the Western diet is loaded with them. Remember the Food Pyramid recommended 11 servings of cereals and bread per day! This is suicide in slow motion. Before the Food Pyramid, there was no adult onset diabetes epidemic.glucose-a1c-blood

So it’s simple. Cut the sugar, cut the starch, measure. You don’t have to wait a year to find out. Get a test after three months. Get your doc to give you a prescription, or get one on line. These tests cost around $25.

Isn’t no sugar/starch dangerous? Couldn’t sugar get too low?

If you are an adult onset diabetic that takes insulin, this is a possibility. However, it means you have so successfully cut sugar that you don’t need insulin anymore. But taper down under your doc’s guidance. If you have lowered you starch/sugar intake enough to have this risk, you have basically won the battle, just get off the insulin.

OTHERWISE, it’s fine. No sugar and no starch will not do any harm at all. If it did, we wouldn’t be here. Inuit still eating the traditional diet get almost none. Many other hunter gatherer tribe get almost none. There are still around 200 tribes, and we are genetically identical, so there is no “they are adapted, we are not” sort of story.

What about the brain needing sugar?

Your body is way ahead of you. Whenever the brain needs something, it gets first dibs. Muscles and other cells aren’t allowed to use glucose unless there is a surplus. Plus the liver has five ways to make glucose. But even if this fails, the liver has another trick up its sleeve. It will convert fat into ketones, and the brain runs fine on these. Perhaps it runs better. People with Alzheimer’s show marked cognitive improvement when placed on a ketogenic diet (practically no carbs at all). Also people who suffer nearly uncontrollable seizures have many fewer seizures on a ketogenic diet.

Consider Cutting Down or Cutting Outglucose-a1c-carbs-sugar

We get far more sugar and starch than we are “designed” to handle. Even amounts that seem small may overload us and send the glucose numbers dangerously up. We simply aren’t evolved to deal with excess starch and sugar. If you cut down, your A1C and fasting glucose numbers will drop. This is highly desirable. In fact, it is hard to avoid degenerative disease if these two numbers are not under control.

Note that if you cut, you will crave carbs for perhaps 4-6 weeks, maybe as long as 12. This is because your cells need time to adjust to switch from carb burning to fat burning. But they inevitably will, after which, carbs and sugar will seem rather funny tasting. You will also weigh less and have more energy.



  8 comments for “Understanding Glucose and A1C Numbers

  1. Jim
    July 19, 2015 at 5:20 am

    Dr. Mike,
    Is there a measure of uncertainty with blood tests like A1c? Coming from a statistical background, I wonder about the variability in a measure (as well as other sources of variation involved – measurement technique, random error, etc…). So an A1c of 5% might be 5% +/- ??%.

    • September 30, 2015 at 10:11 am

      Hi Jim,
      There are a whole host of issues that can effect the A1c number from whether you are a menstruating woman – alters the age distribution of hemoglobin molecules – to whether you took a long bike ride in the days before the test – a transient exercise induced anemia for example – besides the issue you raise of precision vs. accuracy. However, Jim, from having done this thousands upon thousands of time I continue to be impressed with how stable this value really seem to be. Dr. Mike

  2. BOB
    September 29, 2015 at 9:10 pm


    • September 30, 2015 at 10:03 am

      Some lab values reflect entire population statistical norms and some are ‘politically’ determined. “High cholesterol” is an example as is “High A1c.” The numbers set as targets are not those of large population norms but rather what some group thinks reflect disease or near disease states. An A1c of 6.0 was once considered the mark of diabetes; this has now been changed to 6.5. “Pre-diabetes” or “Borderline diabetes” was once thought to occur at 5.5 but is now generally thought to start at 5.7. The cut off points of such numbers are in flux. There are both financial considerations – how do we get insurance companies to pay for this test? – and ‘turf war’ issues between competing medical interests – do the numbers associated with cardiovascular or endocrine disease set the norms? – that drive the numerical cut off points for these and other values. The ‘high cholesterol’ number does not reflect meaningful disease risk – but very clearly the interests of pharmaceutical companies – whereas the ‘high A1c’ actually underestimates the statistical point of increased risk. Alternatively your potassium normal range is just that derived from a large statistical pool; so far no politics in that one. So, Bob, if I have not further confused you, be clear that you would likely be healthier if your A1c were lower, no matter what some organization agrees to call ‘normal.’ Dr. Mike

  3. Ann Yakimovicz
    April 30, 2017 at 7:00 pm

    Having read your book and followed its recommendations and the cookbook for about 6 months (3 blood test periods), I’m doing great with the lipid management and stress management groups. I am finding that the fasting glucose is the toughest to change. With cutting out all sugar and grains except 1 weekly English muffin for Sunday breakfast, and northern fruit (frozen, unsweetened) in a breakfast smoothie, A1C has dropped from 5.5 to 5.3. But, fasting glucose has been the same every time for over a year – 88. I think the fruit may be the cause, but it’s not easy to find solutions for breakfast that my spouse will eat, too.

    • May 2, 2017 at 4:01 pm

      Hi Ann,
      This is a tough one; if your candy-maker – one of my euphemisms for the liver – decides that 88 is your setpoint then it will maintain that number with eerie precision by synthesizing and releasing glucose out of any food source to maintain that number. You will need to convince your liver that you are serious and will be consistent about your carb limitation. Something as simple as your weekly English muffin may be enough to ‘convince’ your liver that it need not reset/change the setpoint. I’ve seen remarkably small deviations from ‘perfection’ be enough to prevent the reset. However I must admit too, that your having brought A1c down from 5.5 to 5.3 is proof a job well done. Try to go the extra mile to see if your liver will reset. Dr. Mike

  4. Barbara
    November 11, 2017 at 8:53 am

    Dear Dr. Mike,
    what about people cutting carbs who are borderline underweight and have difficulty gaining weight? I.e. – me. The A1C has been for many years at 5.2 and now moved to 5.6. But I keep being urged to eat carbohydrates, because of my weight. Cutting them and eating protein, fat and vegetables only (have been on a paleo diet for about 1 yr) has not helped in any way, rather made me thinner than heavier and made my blood tests worse – not better. I am not very good at digesting proteins and animal fats. Any ideas on how to change the diet? Many thanks!

    • November 15, 2017 at 8:54 am

      Hi Barbara,
      Forgive the brief response but I want to endorse your sense that a paleo diet may not be right for you. I have a number of patients for whom starches must be a significant part of their dietary base. I can’t strongly say this is true of you as you don’t have some of the markers, including fasting and postprandial insulin and triglycerides, that would make your issues clearer. Another issue not addressed in your remarks is your muscle mass. If you are thinner but more muscular that is one thing but if you are losing, or at least not maintaining, muscle mass then that too can be an issue. So…you need more data, but do not be intimidated that your sense of what works for you is necessarily wrong. More data needed and trust your sense that something needs to change. Forgive the vague guidance – just the nature of blogs – but find someone who will measure more data points and will work with you to establish a sound baseline and then will work with you to track and change your trendlines of markers you want to make better, Dr. Mike

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