Every 3 months, or whenever we get around to it, those of us with diabetes find ourselves getting that all-important A1C lab test that gauges how were managing our blood sugar levels over time. This can be a lot of pressure, especially when weve put in a whole bunch of work in hopes of seeing some improvement.

The American Diabetes Association generally recommends aiming for an A1C of 7 percent or less for both adults and children with type 1 diabetes (T1D). But recent research shows that only a minority of patients reach those goals.

Because, frankly, diabetes can be maddeningly unpredictable so most of us struggle along in pursuit of lowering our A1C, with constant worry about not hitting the mark.

Have you ever wondered what the highest A1C in history might be? Who would even hold this dubious record, and how high is it possible to go without falling into a coma with any type of diabetes?

DiabetesMine investigated this issue because inquiring minds like to know.

We began by looking in the Guinness Book of World Records, of course. Oddly, the Guinness staff dont seem to have any listings related to A1Cs. They do, however, report that Michael Patrick Buonocore survived a blood glucose (BG) level of 2,656 milligrams per deciliter (mg/dL) upon admittance to the ER in March 2008 in East Stroudsburg, Pennsylvania. Buonocore was just a kid at the time, and that record-high sugar level led his parents to eventually launch a nonprofit called Michaels Miracles that provides financial assistance to families with T1D in need.

So does Buonocore also hold the record for highest A1C?

No, he doesnt. Thats because while hes living proof that its possible to survive stratospheric blood sugar levels, a skyscraping A1C requires both altitude and time. Remember that A1Cs provide a 3-month average of our blood sugars. Individual high BG readings, even crazy-high ones, dont alter the test as much as youd think if they last only a short time. Because T1D presents in children so quickly, Buonocores actual A1C level at diagnosis would probably have been rather middle of the road. It takes a long, slow burn to make an A1C boil.

But just to be sure, I reached out to his parents, who told me that his A1C was 11.9 percent at diagnosis. Higher than we expected but not too high given the four-digit BG reading.

The highest A1C turns out to be a tricky piece of data to ferret out. If you try Google, you find a gazillion people talking about their own personal highest A1Cs and comparing notes with others.

Most A1C point-of-care machines cap out at a certain number, including those at-home testing A1C kits you can buy online.

At the federal clinic where Id worked for over a decade, our A1C results capped out at 14 percent. If the A1C is higher than that particularly at T2D diagnosis time the machine just reads >14%. How much higher is anyoneguess. It could be 14.1 percent, or it could 20 percent.

If you do the math, clocking a 14 percent means youre possibly experiencing a 24-7-90 (24 hours a day, 7 days per week, for 90 days) blood sugar average of 355 mg/dL.

Of course, labs can calculate higher A1Cs. Personally, the highest Ive ever seen is an A1C result in the low 20s. If your A1C was, say 21 percent, it would take a 3-month average blood sugar of 556 mg/dL.

How is that possible? If your blood sugar were in the 500s, wouldnt you go into a coma long before the 3 months were up? Those with T1D would, but those with T2D do not generally go into comas because they have insulin in their bodies all the time, even if they cant process it well enough to keep their BG at safe levels.

Now, coma-free does not mean problem-free. Blood sugar levels this high are toxic. People diagnosed with sky-high A1Cs are generally also diagnosed with complications right out of the gate most commonly retinopathy and sometimes kidney and nerve damage, as well.

But that doesnt answer the question of the unfortunate individual who holds the record for highest A1C ever.

Someone I know mentioned theyd once seen a 27 percent A1C, but thats hard to believe without any documentation to back it up. In asking my own healthcare colleagues, I posed this question online to a group of endocrinologists: Whats the highest A1C youve ever seen, or whats the highest youve ever heard a colleague talk about?

I had my money on 35 percent. That would be a 3-month blood sugar average of 1,000 mg/dL. But the answers I got were surprising, as none of my esteemed colleagues had ever seen or heard of A1Cs as high as I had commonly seen in my clinic in New Mexico.

Dr. Silvio Inzucchi at the Yale School of Medicine is a diabetes guru who wrote a go-to e-book for clinical facts, Diabetes Facts and Guidelines. He told DiabetesMine, The highest we usually see is in the 12-14 percent range, though I think Ive seen an 18 percent a long time ago.

In the same ballpark is Donna Tomky, a New Mexico nurse practitioner and diabetes educator who has been past president of the American Association of Diabetes Educators (now the Association of Diabetes Care and Education Specialists).

Over the years, Ive seen an A1C as high as 19 percent in a type 1 individual who purposely omitted insulin and was admitted for DKA, she said.

In terms of youth and children, Dr. Shara Bialo, a pediatric endocrinologist and fellow T1D in New Jersey, told DiabetesMine that her clinic uses the same point-of-care A1C test that only goes as high as 14 percent. But when one of her patients lands in the hospital, a serum draw is done to determine that persons A1C.

The highest I have seen personally is a 17 percent, but my colleague had a patient with a 19 percent, she said, noting both were teenagers with established T1D and one of whom just found out she was pregnant.

Dr. David Hite, a diabetes education consultant based in California, reports: I had a patient in the clinic with a 17 percent. Thats rare. I usually see new diabetics in the clinic under 14 percent. They come in because they feel like crap and cant tolerate conditions needed to get it lower.

Well-known USC Keck School of Medicine endocrinologist Dr. Francine Kaufman (who now serves as chief medical officer of Senseonics, Inc.) took the top prize in my straw poll with her one-word answer: 22 percent. Repeat after me: Wow!

If youre wondering why the results arent generally higher, that may be because endos and diabetes specialty clinics usually see those with T1D, people who cant survive long in the high-octane environment needed to clock those dangerously high A1C scores. That honor has to go to our T2D cousins, who are typically seen by general practitioners and primary care doctors.

Often, surveys of those physicians show initial high A1C results at the time of T2D diagnosis, with those results lowering dramatically after the T2D patient begins to be treated.

The American Association of Clinical Chemistry is the leading authority on these diagnostic lab tests, and Dr. Darci Block is one of the big wigs whos been a part of the Mayo Clinics Clinical Core Laboratory Services Division. While some lab tests can show higher results than a clinics point-of-care method, she wonders why it would matter just how high a particular result is above 14 percent. To her, anything over 14 is so poor that it becomes not clinically important given the already-urgent need to address the diabetes management, Block says.

Then again, other experts do believe that lowering an A1C of 22 percent at diagnosis to 17 percent could be clinically important. Its certainly an indication that the patient is on the right path.

But Block also points out that crazy-high A1C test results likely have a significant error range. For what its worth, she says shes personally never seen readings higher than 17 percent in her career.

Dr. David Goldstein, the University of Missouri Health Sciences Center Diabetes Diagnostic Laboratory, said he didnt know of any group or company that keeps track of high A1Cs. But he personally has seen an 18 percent result, reflecting a plasma glucose of roughly 400 mg/dL. In newly diagnosed T1D children, the average A1C is about 10 to 12 percent, he said similar to what was recorded in Buonocore, the boy who marked the highest single BG reading in history in the Guinness Book of World Records.

But Goldstein went on to point out an interesting fact that no one else did.

There is a practical limit to how high the A1C can get because the kidneys filter out and excrete glucose from the blood when the plasma glucose level gets over 180 to 200 mg/dL, he said. This is called the renal threshold for glucose, and it differs among people. Only in people with kidney failure or with a high renal threshold can the plasma glucose level be sustained at a high enough level to result in a very high A1C.

That means while we may not be able to conclusively figure out the highest A1C ever, the experts make it clear that whoever holds that dubious honor also has ruined kidneys. This brings us back to Blocks assertion that too high is just too high, and the specific digits dont really matter.

Maybe shes right there. Renowned diabetes educator and author Gary Scheiner of Integrated Diabetes Services in Pennsylvania put it more colorfully. About any A1C above 12 percent, he said: At that high, theres no way the patient could possibly be thinking clearly. A little bird should pop up and just start humming Purple Haze.'

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In Search of the Highest Diabetes A1C Result in History - Healthline