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diabetes FAQ: bg monitoring (part 2 of 5)

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Archive-name: diabetes/faq/part2
Posting-Frequency: biweekly
Last-modified: 9 December 2007

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Changes: see part 1 of the FAQ for a list of changes to all parts.


Subject: READ THIS FIRST Copyright 1993-2007 by Edward Reid. Re-use beyond the fair use provisions of copyright law and convention requires the author's permission. Advice given in m.h.d is *never* medical advice. That includes this FAQ. Never substitute advice from the net for a physician's care. Diabetes is a critical health topic and you should always consult your physician or personally understand the ramifications before taking any therapeutic action based on advice found here or elsewhere on the net.
Subject: Table of Contents INTRODUCTION (found in all parts) READ THIS FIRST Table of Contents GENERAL (found in part 1) Where's the FAQ? What's this newsgroup like? Abuse of the newsgroup The newsgroup charter Newsgroup posting guidelines What is glucose? What does "bG" mean? What are mmol/L? How do I convert between mmol/L and mg/dl? What is c-peptide? What do c-peptide levels mean? What's type 1 and type 2 diabetes? Is it OK to discuss diabetes insipidus here? What is it? How about discussing hypoglycemia? Helping with the diagnosis (DM or hypoglycemia) and waiting Exercise and insulin BLOOD GLUCOSE MONITORING (found in part 2) How accurate is my meter? Ouch! The cost of blood glucose measurement strips hurts my wallet! What do meters cost? Comparing blood glucose meters How can I download data from my meter? I've heard of a non-invasive bG meter -- the Dream Beam? What's HbA1c and what's it mean? Why is interpreting HbA1c values tricky? Who determined the HbA1c reaction rates and the consequences? HbA1c by mail Why is my morning bg high? What are dawn phenomenon, rebound, and Somogyi effect? TREATMENT (found in part 3) My diabetic father isn't taking care of himself. What can I do? Managing adolescence, including the adult forms So-and-so eats sugar! Isn't that poison for diabetics? Insulin nomenclature What is Humalog / LysPro / lispro / ultrafast insulin? Travelling with insulin Injectors: Syringe and lancet reuse and disposal Injectors: Pens Injectors: Jets Insulin pumps Type 1 cures -- beta cell implants Type 1 cures -- pancreas transplants Type 2 cures -- barely a dream What's a glycemic index? How can I get a GI table for foods? Should I take a chromium supplement? I beat my wife! (and other aspects of hypoglycemia) (not yet written) Does falling blood glucose feel like hypoglycemia? Alcohol and diabetes Necrobiosis lipoidica diabeticorum Has anybody heard of frozen shoulder (adhesive capsulitis)? Gastroparesis Extreme insulin resistance What is pycnogenol? Where and how is it sold? What claims do the sales pitches make for pycnogenol? What's the real published scientific knowledge about pycnogenol? How reliable is the literature cited by the pycnogenol ads? What's the bottom line on pycnogenol? Pycnogenol references SOURCES (found in part 4) Online resources: diabetes-related newsgroups Online resources: diabetes-related mailing lists Online resources: commercial services Online resources: FTP Online resources: World Wide Web Online resources: other Where can I mail order XYZ? How can I contact the American Diabetes Association (ADA) ? How can I contact the Juvenile Diabetes Foundation (JDF) ? How can I contact the British Diabetic Association (BDA) ? How can I contact the Canadian Diabetes Association (CDA) ? What about diabetes organizations outside North America? How can I contact the United Network for Organ Sharing (UNOS)? Could you recommend some good reading? Could you recommend some good magazines? RESEARCH (found in part 5) What is the DCCT? What are the results? More details about the DCCT DCCT philosophy: what did it really show? Is aspartame dangerous? IN CLOSING (found in all parts) Who did this?
Subject: How accurate is my meter? bG (blood glucose) meters are not as accurate as the readings you get from them imply. For example, you might think that 108 means 108 mg/dl, not 107 or 109. But in fact all meters made for home use have at least a 10-15% error under ideal conditions. Thus you should interpret "108" as "probably between 100 and 120". (Similar considerations apply if you measure in units of mmol/L.) This is a random error and will not be consistent from one determination to the next. You cannot expect to get exactly the same reading from two checks done one after the other, nor from two meters using the same blood sample. This is generally considered acceptable because variations in this range will not make a major difference in treatment decisions. For example, the difference between 100 and 120 may make no difference in how you treat yourself, or at most might make a difference of one unit of insulin. With present technology, more accurate meters would be much more expensive. This expense is only justified in research work, where such accuracy might detect small trends which could go undetected with less accurate measurements. This discussion applies to ideal conditions. The error may be increased by poor or missing calibration, temperatures outside the intended range, outdated strips, improper technique, poor timing, insufficient sample size, contamination, and probably other factors. Contamination is especially serious since it can happen so easily and is likely to result in an overdose of insulin. Glucose is found in fruits, juices, sodas, and many other foods. Even a smidgen can seriously alter a reading. When comparing meter readings with lab results, also note that plasma readings are 15% higher than whole blood, and that capillary blood gives different readings from venous blood. Visually read strips are slightly less accurate than meters, with an error rate around 20-25%. For some meters, strips are available from manufacturers other than the meter manufacturer. Some m.h.d. readers have compared the strips side- by-side and found those from one manufacturer to read consistently lower than the strips from another. The differences are not likely to make a significant difference in your treatment, but are large enough to be noticeable and possibly confusing. For this reason it is not a good idea to change strip manufacturers without comparing the readings from one with the readings from the other. I've seen no such direct comparison of meters, but the possibility exists that some meters might read consistently lower than others. Be careful when changing meters. By "error rate" I mean twice the standard deviation from the mean. An error rate of 15% says that about 95% of the readings will be within 15% of the actual value.
Subject: Ouch! The cost of blood glucose measurement strips hurts my wallet! The cost of blood glucose measurement strips is a complex interaction of R&D costs, manufacturing costs, marketing strategy, insurance practices, and undoubtedly other factors. You can ask on the net if you want; you'll get lots of comments but no answers. There are a few of ways of reducing the cost of blood glucose monitoring. One is to seek out the best price for the strips; large stores such as Costco often have good prices, as do some online order suppliers. A second way is to choose a meter with lower cost strips. Your health care team may be familiar with and prefer a particular meter, but it's not likely that they considered cost in making their choice. If you insist that you need a lower cost system, they should be willing to work with you. All meters now on the market are adequately accurate for home use, so if you are getting strips under insurance, you are generally safe in using the preferred brand under your plan. At one time, you could use visually read strips (such as Chemstrip bG) and cut them in half. This type of strip has mostly disappeared from the market as of 2007 and the prices on any remaining is high, so this is no longer a viable option. Most discussion on m.h.d of the cost of blood glucose measurement strips has centered on the US. I'm not sure why, though a good guess is that differences in health care systems and national policies make this issue more critical to the individual patient in the US. There is no dearth of non-US participants on m.h.d.
Subject: What do meters cost? The flip side of expensive blood glucose measurement strips is that the manufacturers virtually (and sometimes literally) give away the meters to hook you on their strips. Don't pay full price for a meter; look for discounts, rebates, and giveaways. There is even a brand of strips which includes a basic meter in the top of each vial; the price is OK and as far as I know the accuracy is as good as any. Make sure you consider the cost of strips as well as the cost of meters, and find out which your insurance will pay for. The most fully featured meters don't have such widely advertised deals, though you can probably find ways of getting them at discount. Decide whether you need a meter with a lot of extra features or just a basic one. As of 2007, even most basic meters allow you to download results into a computer. If you have insurance that pays for strips but not for the meter, you should not have to pay anything for the meter. Most like it will be provided to you so that you can use the preferred strips. If not, and if it's worth the time to you, call the meter manufacturers' customer service departments or the online suppliers. They will very likely find a way to get you the meter for free. The manufacturers make most of their profit on the strips, not on the meters. As with strips, this discussion of costs applies to the US, and there has been little discussion of meter costs outside the US on m.h.d., probably because fewer tradeoffs are available in most countries. In Britain, strips are covered by the National Health Service, but meters may be expensive. However I've also heard of a limited-time One Touch program providing a full refund for the meter if you submit the strip wrappers. Likely other companies will compete. (This information is from the 1990s, and I do not know if it is current.) Elsewhere? Please post. It's likely that the situation is continuing to change rapidly, so if the cost of the meter is painful for you, investigate other options before paying full price -- wherever you live.
Subject: Comparing blood glucose meters The ADA has a wealth of information on diabetes-related products, including meters, at http://www.diabetes.org/diabetes-forecast/resource-guide.jsp This URL has changed in the past and might change again.
Subject: How can I download data from my meter? When I originally wrote this section, download capabilities were rare. Now, almost every meter maker provides this capability, with the possible exception of some house-brand meters and very small meters. As a result, I have removed much of the original information. A great deal of information on diabetes-related software of all kinds can be found on David Mendosa's web site, http://mendosa.com. Most meter makers charge extra for the cable and software for downloading. The cables usually include electronics, and so are not easily duplicated. Much of the software on David Mendosa's web site is third party software which can download from a variety of meters. LifeScan publishes the download protocol, or at least did at one time. You can download a copy of those specs from One Touch II: ftp://vic.cc.purdue.edu/pub/ One Touch Profile: ftp://vic.cc.purdue.edu/pub/ Vic Abell <abe(AT)purdue.edu> has long provided a simple free DOS program, TOUCH2, to download and analyze One Touch II and Profile data. This was probably the first widely available third-party program to analyze meter data. TOUCH2 interfaces to the data port of the One Touch, downloads the data on command, and provides a variety of analytical displays. I do not know whether it works with all the latest LifeScan models. It's available in a couple of forms via anonymous ftp from vic.cc.purdue.edu in the /pub directory, or using a web browser, ftp://vic.cc.purdue.edu/pub/
Subject: I've heard of a non-invasive bG meter -- the Dream Beam? *** The following information is incomplete, as another company has introduced a non-invasive meter for about $8000. It has been discussed in the newsgroup. Rumors of other non-invasive (and "non-evasive") meters abound. I won't be trying to keep this section up to date until the situation stabilizes. *** *** Note that as of 2007, we are no closer to having a non-invasive meter than when I wrote the following over ten years ago. A minimally invasive meter and two or three continuous meters using embedded probes exist, but their accuracy leaves a lot to be desired. There is at least one development project in hot pursuit of a bG monitor which operates by shining light through flesh (through the thumbnail in one case) and analyzing the light that passes through. Glucose doesn't affect light much differently from many other substances in the body, so this is not an easy task. Some field trials have been done, but the developers have a way to go to reach acceptable accuracy. A successful product is far from guaranteed, and may be several years away if it arrives at all. One estimate is that such a meter might cost about US$1000. Assuming the per-check cost is zero, this would pay for itself in 1-2 years for many patients. Look for the insurance companies to throw up some roadblock to achieving these savings, at least in the US.
Subject: What's HbA1c and what's it mean? Hb = hemoglobin, the compound in the red blood cells that transports oxygen. Hemoglobin occurs in several variants; the one which composes about 90% of the total is known as hemoglobin A. A1c is a specific subtype of hemoglobin A. The 1 is actually a subscript to the A, and the c is a subscript to the 1. "Hemoglobin" is also spelled "haemoglobin", depending on your geographic allegiance. Glucose binds slowly to hemoglobin A, forming the A1c subtype. The reverse reaction, or decomposition, proceeds relatively slowly, so any buildup persists for roughly 4 weeks. Because of the reverse reaction, the actual HbA1c level is strongly weighted toward the present. Some of the HbA1c is also removed when erythrocytes (red blood cells) are recycled after their normal lifetime of about 90-120 days. These factors combine so that the HbA1c level represents the average bG level of approximately the past 4 weeks, strongly weighted toward the most recent 2 weeks. It is almost entirely insensitive to bG levels more than 4 weeks previous. In non-diabetic persons, the formation, decomposition and destruction of HbA1c reach a steady state with about 3.0% to 6.5% of the hemoglobin being the A1c subtype. Most diabetic individuals have a higher average bG level than non-diabetics, resulting in a higher HbA1c level. The actual HbA1c level can be used as an indicator of the average recent bG level. This in turn indicates the possible level of glycation damage to tissues, and thus of diabetic complications, if continued for years. Interpreting HbA1c values can be tricky for several reasons. See the following section for more details.
Subject: Why is interpreting HbA1c values tricky? Interpreting HbA1c values is tricky for several reasons: differing lab measurements, variation among individuals, and misapprehension of the relevant timeframe. First trick: several different lab measurements have been introduced since 1980, measuring slightly different subtypes with different limits for normal values and thus different interpretive scales. A National Glycohemoglobin Standardization Program began in 1996, sponsored by the American Diabetes Association and others. See reference 1. This program certifies HbA1c assays which conform to the method used in the DCCT. However, as of 1998 other versions are still in use in many places, both in the US and elsewhere. When you get a lab result, be sure to look at what the lab considers to be the normal range. Most discussion of HbA1c values in m.h.d appears to be based on the DCCT, where the normal range is approximately 3.0-6.1%. Caveat lector. (See part 5, Research, of this FAQ for more information on the DCCT, the Diabetes Control and Complications Trial.) Second trick: HbA1c levels appear to vary by up to 1.0% among individuals with the same average bG. See reference 2. This is very recent research and its implications are not yet clear. The actual reaction rates governing the formation of HbA1c may vary among individuals. Some of the variation may be due to differences in erythrocyte (red blood cell) survival times -- the rough 90-120 day range noted earlier -- although other work limits this to a small part of the total variation (see reference 5). Variations in the HbA1c formation rate may or may not correlate with the rate of damage to other tissues. While we await further research, we can only say that differences of 1.0% from one individual to another may not be meaningful. Although HbA1c varies among individuals with the same average bG, it is very stable for any given individual. Thus a change of 1.0% in your own HbA1c is definitely meaningful. Third and final trick: most medical professionals have been given incorrect information about the timeframe which HbA1c represents. Even textbooks normally state the 90-120 day average, as does the American Diabetes Association in its Position Statement on Tests of Glycemia in Diabetes (see reference 1). The longer estimate is based on the assumption that the conversion of hemoglobin A to HbA1c is essentially irreversible. This was a reasonable assumption before the reaction rates were actually measured. See the following section for information about the research which measured the reaction rates and simulated the consequences. See the following section for the references mentioned above.
Subject: Who determined the HbA1c reaction rates and the consequences? In the early 1980s, Henrik Mortensen and colleagues at Glostrup University Hospital, in Denmark, measured the reaction rates in vitro. Their results showed the assumption of irreversibility to be untrue. In fact the reverse reaction (HbA1c to HbA and glucose) proceeds at about 1/8 the rate of the forward reaction, which is very far from irreversible. Mortensen et alia also built a biokinetic model based on the measurements, and validated the model by comparing its predictions to actual patients. See references 3-5. Among other things, Mortensen's work shows that after a change in average bG level, the HbA1c level restabilizes after about 4 weeks. This has several consequences. Clinically, the most important are these: First, the HbA1c is an exponentially weighted average of blood glucose levels from the preceding 4 weeks, with the most recent 2 weeks being by far the most important. Second, measuring HbA1c less often than monthly results in unmonitored gaps between measurements. To use HbA1c as a continuous monitoring tool, you need to check it at least once a month. Third, it is worthwhile checking the HbA1c of newly diagnosed patients as often as once a week to determine the effectiveness of the newly imposed treatment. Reference 1: American Diabetes Association, Tests of Glycemia in Diabetes, Diabetes Care 23:S80-S82, January 2000 Supplement 1. This specific issue is no longer available online, but the most recent version is available at http://diabetes.org/cpr/. Reference 2: Kilpatrick ES, Maylor PW, Keevil BG: Biological Variation of Glycated Hemoglobin. Diabetes Care 21:261-264, February 1998. Abstract available on the web at http://care.diabetesjournals.org/cgi/content/abstract/21/2/261. Reference 3: Mortensen HB, Christophersen C: Glucosylation of human haemoglobin a in red blood cells studied in vitro. Kinetics of the formation and dissociation of haemoglobin A1c. Clinica Chimica Acta 134:317-326, 15 November 1983. Reference 4: Mortensen HB, Volund A, Christophersen C: Glucosylation of human haemoglobin A. Dynamic variation in HbA1c described by a biokinetic model. Clinica Chimica Acta 136:75-81, 16 January 1984. Reference 5: Mortensen HB, Volund A: Application of a biokinetic model for prediction and assessment of glycated haemoglobins in diabetic patients. Scandinavian Journal of Clinical and Laboratory Investigation 48:595-602, October 1988.
Subject: HbA1c by mail You may find it cheaper and/or more convenient to have your HbA1c measurements done by mail -- and you collect the sample by fingerstick. As far as I know, the tests mentioned here are as accurate as those done by major labs. Diabetes Technologies (http://diabetestechnologies.com) provides a "Accu-Base A1c Test Kit". The cost is $26 per kit plus $6 S/H, with discounts for multiples, which includes the laboratory analysis. All needed supplies are provided, including a lancet and postage to the lab. The procedure is simple: they provide a capillary tube already attached to a clip. Stick your finger (using a one-use lancet they provide, if you wish) and touch the end of the tube to the drop until the tube is full -- a fraction of a second to a few seconds. Drop the tube into a small vial with fluid in it (pre-filled) and shake for a few seconds. Fill out a little paperwork. Pack the vial in a Biopack, padding and package, all provided and even prestamped. Drop it in the mail. You provide: writing pen, blood, tissue paper for the excess blood. The lab analyzes the sample using HPLC (high performance liquid chromatography). This is the same as the major labs use. In other words, Quest or LabCorp take an entire vial of blood and use one drop. Diabetes Technologies is in Thomasville, GA. Their phone number is 888-872-2443, and their web site is http://diabetestehnologies.com. Flexsite Diagnostics (http://flexsite.com) offers a single-test kit for $20, four for $60, and they accept Medicare reimbursement. The test requires two drops of blood, which must dry overnight on a paper collector before mailing. They offer priority or express mailing (both ways) for $10 and $30 additional, although I gather they do not promise that the test itself will be processed any faster. Darrell Hervey <bpd318(AT)aol.com> reports that his experience with Flexsite was excellent. Biosafe (http://ebiosafe.com) sells a mail-in "Biosafe Diabetes (A1C) Test", which uses a collection card similar to the Flexsite procedure. It is available directly from Biosafe and from various online merchants for around $25. I have serious problems with Biosafe due to their use of the term "diabetes test", which implies that A1c is to be used for diagnosing diabetes, which is totally contrary to ADA recommendations. They even have another "Diabetes Risk Assessment" kit, which explicitly uses A1c as one part of the assessment. Because of their recommendations which are contrary to ADA positions, I cannot recommend the Biosafe kits. Express-Med used to make a kit which I used once, but they no longer sell it. It was similar to the kit now sold by Flexsite. Becton-Dickinson (BD) was advertising a HbA1c kit in 1998. However, the last time I spoke with someone there, they were only distributing it through health care organizations (such as HMOs) and plans for individual sales were indefinite. A personal note: I used the Diabetes Technologies kit, and a predecessor supplied by Diabetes Support Systems, for several years starting in 1996. Without this service, I probably would have had at most one HbA1c measurement per year due to the cost and the inconvenience of visiting the lab or doctor's office -- and I really needed the tests at times. I am not currently using the service as of 2007, only because my insurance provides the test free at Quest. (Some updates applied December 2007. Other options may be available.)
Subject: Why is my morning bg high? What are dawn phenomenon, rebound, and Somogyi effect? This section is written by Charles Coughran <ccoughran(AT)ucsd.edu>. There are three main causes of high morning fasting bg. In decreasing order of probability they are insufficient insulin, dawn phenomenon, and Somogyi effect (aka rebound). Insufficient or waning insulin is simple. If the effective duration of intermediate or long acting insulin ends sometime during the night, the relative level of circulating insulin will be too low, and your blood sugars will rise. Dawn phenomenon refers to increased glucose production and insulin resistance brought on by the release of counterregulatory hormones in the early morning hours near waking. It happens in normal people as well as in diabetics; in nondiabetics it shows up as measurably increased insulin secretion around dawn. Dawn phenomenon is variable in strength both within the population and over time in individuals. It can show up as either high fasting glucose levels or an increased insulin requirement to cover breakfast compared to equivalent meals at other times of day. Somogyi effect refers to a rebound in bg after nocturnal hypoglycemia which occurs during sleep with the patient not experiencing any symptoms. The hypoglycemia triggers the release of counterregulatory hormones. Somogyi effect appears to be less prevalent than previously thought. While it does occur, some episodes of hyperglycemia following hypoglycemia are actually waning insulin levels following an insulin peak with medium acting insulin. This can be difficult to sort out. The best way to sort it out is to test every couple of hours from bedtime to morning. If your bg rises all, or much of the night, it is a lack of circulating insulin. If it is stable all night, but rises sharply sometime before you wake in the morning, it is dawn phenomenon. If your bg declines to the point of a hypoglycemic reaction, it is *possibly* Somogyi effect. You may have to test on several nights to nail the problem. Once you have figured out the problem you and your doctor can discuss changes in your insulin regimen to correct it. The answer depends critically on your particular circumstances. Mayer Davidson, in _Diabetes Mellitus: Diagnosis and Treatment_ (p 252 in the 3rd edition) says that Somogyi effect rarely causes fasting hyperglycemia, and cites studies.
Subject: Who did this? -- Edward Reid <edward@paleo.org.SPAMNOT> Tallahassee FL -- Art works by Melynda Reid: http://paleo.org y Melynda Reid: http://paleo.org

User Contributions:

Raqiba Shihab
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May 10, 2012 @ 2:14 pm
Many thanks. My husband has Type 2 diabetes and we were a bit concerned about his blood sugar/glucose levels because he was experiencing symptoms of hyperglyceamia. We used a glucometer which displays the reading mg/dl so in my need to know what the difference
between and mg/dl and mmol/l is, i came across your article and was so pleased to aquire a lot more info regarding blood glucose, how to read and convert it.
Bhavani
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Aug 11, 2012 @ 9:09 am
It was really informative and useful for people who don't know conversion. Thanks to you

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