Glucometer accuracy, potassium supplementation

[MarcR]

As I mentioned here, of late my fasting blood glucose readings have been in prediabetic (>100 mg/dL, >5.6 mmol/L) territory. I have put it down to the hopefully benign physiological insulin resistance phenomenon noticed by some ketogenic dieters.

Yesterday I had an annual checkup. I brought my Precision Xtra glucometer and used it after the phlebotomist finished with me - 106 mg/dL (5.9 mmol/L). The lab's spot reading was 16% lower at 89 mg/dL (4.9 mmol/L), and the HbA1c was 4.6%, which corresponds to an estimated average of 85 (4.7).

I poked around a bit and found a study comparing lab venous blood glucose assays to glucometer capillary measurements. On average, the lab assays were 8% lower than the glucometer readings.

I no longer think physiological insulin resistance is an issue for me. Going forward I am going to multiply my glucometer readings by 0.84 prior to interpreting them. I'm happy about this as I will feel more comfortable adding carbs to my diet. Anything that keeps me below about 150 on the glucometer (mid-120s in lab assay terms) is fair game going forward!

In other news, after elevated readings in March and July of last year indicating kidney dysfunction, my creatinine was normal (0.9 mg/dL) once again. I'm pretty sure last year's results were caused by what I now believe was potassium supplementation. Those capsules are limited to 99 mg for a reason, and I now think I was crazy to take 10 of them each day. If anyone else learned about ketogenic dieting from a bunch of body builders, watch out for bro science!

On a related note, the chronic nighttime leg cramps that drove my reckless potassium supplementation finally went away about three months ago when I added magnesium l-threonate to my regimen. Previously I had been relying on the Albion chelated magnesium glycinate that turned out to be fake. YMMV - watch out for bros, including me!

And finally, the lipids. 253 mg/dL (6.5 mmol/L) total, 68 mg/dL (1.8 mmol/L) HDL, 75 mg/dL (0.85 mmol/L) trigs. I have a cardiology referral and plan to get NMR, lp(a), homocysteine, and CIMT in that context.

[Stavia]

Your Hba1c is exceptional. I cant remember ever seeing one that low in a healthy person of our age. IMO you have heaps of leeway for raising carbs.

I'll be very interested in your NMR. Please let is know when it's through.

[KatieS]

Mer, my Freestyle Lite glucometer reads low, 72 with the lab's read of 85, but generally only a few points lower. However, my A1c persists at 5.5 despite very low home readings. Once you see your small LDL-P you can verify that the IR is not an issue. At least that measurement did decline by a third for me. I have boxes of test strips and have used this meter for over three years, so I just note the trends. When I looked into other meters, inaccuracy plagues them all. It seems like we all have measurements that stubbornly don't budge. Your A1c is exceptional and motivates me to fast longer!

Also, my leg cramps & visual migraines are in remission while on Mg-l- threonate: ( as suggested by LillyB.

As to potassium, while on a diuretic for hypertension (only noted after intense exercise at altitude and during a maximal stress echo test) my K averaged 3.6, which if low normal. Switching to losartan for hypertension, I no longer have to limit swimming for fear of foot cramps, so I suspect the diuretic lowered my B vitamins, Mg, not just K. However, I do think it's very important for AD prevention to detect exercise-induced hypertension, a prelude to sustained hypertension. Those with a strong FH of hypertension, might want to consider this type of provocative testing.

Please update us on your upcoming labs & CIMT results.

[GenePoole0304]

have a Freestyle and it has always been right on with strips. if recall estimated variance accuracy is 10% but usually much better.
also have a Prescision Xtra when it works on ketones and doubt its accuracy. could be strips on BG get the pharmacy to check them. changed meter 8x as they told me to return it and sent me new one, the helpline just wastes your time and reads from a cheat sheet then puts you on hold while they check with someone else.

another possible cause of leg cramps is lower hydration you lose it in a.m.

[Julie G]

Hey, Merouleau- really interestng to see how potassium supplementation affected you. I got into trouble with that as well. I relied on my cron-o-meter's data (showing a deficiency) when making my decision to supplement. I was super wobbly for a few months before I realized that wasn't a good idea for me- slow learner I almost passed out every time I stood up; my already low BP became ridiculously low.

You recommended the Precision Xtra for me and I've had good luck. It's always pretty closely jived with serum testing. Congrats on dodging an imaginary problem and on your crazy low A1c . I agree with Stavia, that's the BEST I've ever seen- wow!

Please share as you get more info on advanced lipids and more. I've got my fingers crossed all is well.

[MarcR]

Stavia, Kitano, Gene, Julie, thanks for the feedback.

Also, my leg cramps & visual migraines are in remission while on Mg-l- threonate

That's helpful information. It's good to know that someone else associates Mg-L-T with leg cramp cessation. I used to get ocular migraines occasionally after playing ice hockey - I didn't even know what they were until the topic arose here. I haven't played since I moved in late October, so I don't know if the Mg-L-T prevents them in me, but I'll mention it here if/when I ever get another one.

I do think it's very important for AD prevention to detect exercise-induced hypertension, a prelude to sustained hypertension. Those with a strong FH of hypertension, might want to consider this type of provocative testing.

Thanks for the heads-up. I think I do have a "strong FH" as both of my mid-70s parents have been taking medication for many years to control hypertension. I did not know that exercise-induced hypertension was even a thing, and your remark prompted me to learn about it. Intuitively, it seems analogous to postprandial blood glucose - a critically important biomarker that tends to be neglected because it's inconvenient to measure.

From Exercise-Induced Hypertension, Cardiovascular Events, and Mortality in Patients Undergoing Exercise Stress Testing: A Systematic Review and Meta-Analysis, I learned that "hypertensive response to exercise (HRE)" is a synonym for the phenomenon and that HRE at moderate exercise intensity is a meaningful indicator:

After adjustment for age, office BP, and CV risk factors, an HRE at moderate exercise intensity carried a 36% greater rate of CV events and mortality (95% CI, 1.02–1.83, P = 0.039) than that of subjects without an HRE. Additionally, each 10mm Hg increase in systolic BP during exercise at moderate intensity was accompanied by a 4% increase in CV events and mortality, independent of office BP, age, or CV risk factors (95% CI, 1.01–1.07, P = 0.02).

Fortunately for my own ease of experimentation, moderate intensity seems to be the sweet spot. HRE at maximal workload was not found to be a meaningful indicator.

I have not yet found a precise definition for "moderate exercise intensity", so I settled on a heart rate metric. I know from experience that the "220 minus age" rule of thumb for maximum heart rate applies to me, so I decided that the 160s are "maximum" and the 140s are "moderate". So basically I just took a bunch of blood pressure readings - systolic/diastolic/heart rate - with an Omron HEM-790IT before and immediately following some calisthenic and resistance exercise:

T+0 (resting): 110/64/47
T+10 (after reaching heart rate of 144 bpm): 171/71/113
T+11: 156/65/94
T+12: 151/61/85
T+13: 138/62/78
T+14: 131/58/73
T+15: 131/57/71
T+17: 122/61/70
T+20: 121/57/66
T+21: 108/55/63

The "Reference group" details from the paper's Table 1, which lists the 12 studies that were analyzed, leads me to believe that I'm on the high side of normal but still short of HRE.

This may be a lot more detail than is interesting to most of us, but I'm hoping others have been down this road already or are now inspired to travel it to offer additional perspective. Kitano, was your HRE diagnosed at maximum or moderate exercise intensity? What was the systolic level that caused your doctor to diagnose it? What's normal/healthy for blood pressure during exercise?

[KatieS]

Mer, I saw my B/P go up to 191/100 while the tech was very nervous since I had a benign abnormal EKG change. After the test, I took my mother's hypertension Rx and immediately emailed my doctor for Rx. Note my diastolic B/P shot up, not just the systolic from maximal cardiac output testing on a cycle, no artifact. Your numbers look great to me, but go ahead and share with your cardiologist. My B/P was creeping up before this test, but the 24-hour monitoring test was "normal", but did not read out while I was exercising or playing the sax, so that should have raised suspicions to pursue exercise testing. The review article links IR, endothelial dysfunction and underlying arterial stiffness, probably all conditions that I have.

[MarcR]

Thanks for the additional detail on your situation, Kit. It's helpful to have a concrete example of what can go wrong with BP during exercise.

[MarcR]

You recommended the Precision Xtra for me and I've had good luck. It's always pretty closely jived with serum testing.

After reflecting further on this, I think my high FBG readings may have started when I gave my original Precision Xtra to my parents and bought another one for myself. I think I'll test them both head to head at some point to see if they read differently.

[Stavia]

Merouleau, we dont do the 220 minus age anymore. We aim for systolic less than 140 or 150 depending on which guidelines you follow, but thats validated against bp in a resting state. I see your readings as completely appropriate physiologically. It only took three to four mins to get down to good readings and a few more mins to get to your stellar (I love your american word for excellent, its too cute) baseline.
IMO nothing to worry about, indeed your readings are so good you can feel entitled to boast about them! Though methinks not your style to boast

Ps. no apoe4 bp level recommendations out there, I'm working on 120 systolic as the highest we should be because that's the level we use for another high risk situation, renal impairment.