The weird part of keto bloodwork is this: you can be getting metabolically healthier and still watch HbA1c drift higher. That is not a contradiction, it is a measurement trap, and Mark Kaplan’s story makes it easier to see why. His low-carb approach improved insulin, triglycerides, and inflammation after a heart attack, yet his HbA1c rose because his red blood cells were living longer, giving hemoglobin more time to collect glucose.
The lab number that looks simpler than it is
HbA1c is usually treated as the cleanest snapshot of diabetes control because it reflects average blood glucose over the previous 2 to 3 months. That rule of thumb comes from the typical 120-day life span of a red blood cell, which is the window during which glucose can attach to hemoglobin. The American Diabetes Association also describes A1c as a weighted average, with the most recent glucose exposure carrying more influence than older readings.
That sounds straightforward until red blood cell turnover changes. When red blood cells live longer, hemoglobin has more time to glycate, so HbA1c can rise even if glucose-related markers are improving. When red blood cell survival is shortened, the opposite can happen: HbA1c can look artificially low. The National Glycohemoglobin Standardization Program is blunt about this point, warning that any condition that shortens erythrocyte survival or reduces mean erythrocyte age will falsely lower HbA1c regardless of assay method.
Why keto can make the mismatch more obvious
Very-low-carbohydrate eating often changes the rest of the panel in the right direction. A Frontiers consensus article found that a very-low-carbohydrate diet safely improved HbA1c, weight, blood pressure, triglycerides, HDL cholesterol, white blood cells, C-reactive protein, and alanine transaminase compared with baseline. That is exactly the kind of broad metabolic shift keto followers look for, because it reaches beyond glucose alone.
Kaplan’s case sits inside that pattern. After his heart attack, his low-carb eating improved fasting insulin, triglycerides, and inflammatory markers, yet his HbA1c rose. The explanation is not that his metabolic health worsened. It is that his healthier red blood cells were circulating longer, with some profiles describing survival of up to 145 days, which increases glycation exposure and can nudge the A1c upward.
That is the measurement paradox in plain English. HbA1c is still useful, but it can stop being a faithful proxy when red blood cell lifespan changes. NIDDK notes that the A1c test reflects average blood glucose over the past 3 months and is based on the typical 120-day life span of a red blood cell; it also notes that hemoglobinopathies can make the test less accurate. In other words, the number is only as clean as the biology underneath it.
What to watch alongside HbA1c
If you are doing keto, do not let one rising A1c bury the rest of the data. The markers that mattered in Kaplan’s story were the ones that actually moved with the diet: fasting insulin, triglycerides, inflammatory markers, blood pressure, and body weight. The Frontiers consensus also points to HDL cholesterol, white blood cells, C-reactive protein, and alanine transaminase as markers that can improve on a very-low-carbohydrate diet.
A practical keto bloodwork readout usually looks better when you judge it as a panel, not a single number:
- Fasting insulin, for how hard your pancreas is working
- Triglycerides, for carb sensitivity and lipid handling
- HDL cholesterol, which often rises on low-carb eating
- C-reactive protein and white blood cells, for inflammation
- Alanine transaminase, for liver stress
- Blood pressure and weight, for whole-system change
- HbA1c, but only with context
That context matters because A1c can be distorted by hemoglobin variants and by any condition that changes red blood cell lifespan. The NGSP guidance and NIDDK both point to this problem, and it is why a keto athlete, a post-heart-attack patient, or anyone with unusual blood cell turnover should not treat HbA1c as a stand-alone verdict.
Why Kaplan’s story lands with keto readers
Kaplan is not just a patient with an interesting lab puzzle. Recent profiles describe him as a former ATP professional tennis player who had a heart attack at age 52. They also say he founded HealthTruth, created the AI product Neo, and wrote Unplugged, which became a No. 1 Amazon bestseller in heart disease in its launch week. That background gives his experience a certain blunt credibility, especially when he says his doctors focused on LDL cholesterol while missing other markers in his bloodwork.
That complaint is familiar in the keto world. LDL gets all the airtime, while insulin, triglycerides, inflammation, and liver markers get treated like footnotes, even when they are the numbers changing fastest on low-carb eating. Kaplan’s case does not argue that LDL never matters. It argues that a narrow focus can miss the larger metabolic picture, and that includes a potentially misleading HbA1c.
A 2025 Frontiers study on red blood cell lifespan and HbA1c pushed the same idea further, concluding that adjusting for red blood cell lifespan may improve blood glucose management and diabetes-complication prevention. That is the direction the conversation needs to move in: not just what the HbA1c says, but whether the biology behind the reading makes the number trustworthy.
The keto takeaway is simple enough to keep in your head the next time a lab report looks upside down. If fasting insulin, triglycerides, inflammation, and blood pressure are improving while HbA1c rises, do not panic at the number alone. First ask whether red blood cell lifespan, hemoglobin variation, or another blood-cell issue is bending the reading, because sometimes the marker is lying even when the rest of the panel is telling the truth.
Every story on Keto Diet Magazine is assembled by an automated editorial system that works from verified research, official records, and credible reporting, then clears automated accuracy and moderation checks before it goes live. The standards that system follows are set and overseen by the people who run the publication. Read our full editorial policy.
Did this article answer your question?
