Nerve damage begins before glucose reaches diabetic range. This is the single most consequential thing patients are not told, because it is the window in which the damage is still reversible.
Why “your sugar is fine” is not the same as “your nerves are fine”
The diagnostic thresholds for diabetes were set on the risk of eye and kidney disease. Nerves were not what the cutoffs were drawn around, and small nerve fibers appear to be damaged at glucose levels below those lines.
So a patient with an A1c of 5.9 and burning feet is repeatedly told their sugar is normal. It is normal by a threshold built for a different complication. The nerves are reporting something the number is not designed to capture.
What that means in practice
- Small-fiber symptoms come first — burning, tingling, night pain, hypersensitivity — and they arrive years before numbness.
- Standard nerve conduction testing is often normal, because it measures large fibers. A normal study does not rule this out.
- This is the reversible stage. Small fibers regenerate. Once large-fiber loss is established, the conversation changes.
Both of those points are covered in more detail under small fiber neuropathy and can diabetic neuropathy be reversed.
What we actually look at
A fasting glucose and an A1c are averages and thresholds. Neither shows what happens to you after a meal, which is where the damage is being done.
Post-meal glucose and glucose variability are the informative measurements, and continuous glucose monitoring is how you see them. Two people with an identical A1c can have completely different excursion patterns, and it is the excursions that correlate with nerve injury.
What changes the trajectory
The evidence for intervening at this stage is better than at any later stage, and none of it is exotic. Weight reduction where relevant, changing the shape of the glucose curve rather than only its average, addressing insulin resistance directly, and correcting the other contributors — B12, thyroid, alcohol — that are quietly adding to the injury. See metabolic care.
The addition worth making is measurement. Advice given against a quarterly A1c is advice given blind. Advice given against a two-week continuous glucose trace is specific: this meal, this time of day, this pattern.
Why this matters more than the label
Patients often become preoccupied with whether they meet criteria for diabetes. Clinically it is close to irrelevant here. The nerves do not know where the cutoff is, and waiting to cross it before acting means waiting until part of the damage is no longer recoverable.
If you have burning or tingling feet and have been told your glucose is borderline, that combination is worth investigating properly rather than watching. See also burning feet at night.
To be assessed, call (314) 310-5577 or text (314) 886-5902. We are at 12174 Natural Bridge Rd, Suite 110, St. Louis, MO 63044.
Common questions
My A1c is 5.8. Can that cause neuropathy?
It can be associated with small-fiber damage, yes — particularly where post-meal excursions are large. The threshold for diabetes was not drawn around nerve risk.
The detail is in Diabetic Neuropathy.
My nerve test was normal. Does that settle it?
No. Standard nerve conduction studies measure large fibers. Early diabetic nerve damage is small-fiber and can be present with a normal study.
That is the subject of The Stages of Diabetic Neuropathy.
Is it reversible at this stage?
This is the stage where recovery is genuinely realistic, because small fibers regenerate. That is the argument for acting now rather than waiting.
That is the subject of Peripheral Neuropathy.
Do I need continuous glucose monitoring?
It is the most useful single test at this stage, because it shows variability and post-meal spikes that an A1c averages away.
Can Diabetic Neuropathy Be Reversed? explains what that looks like.
Which supplements are worth taking, and the one to stop.
Sources
- Ziegler D et al. Neuropathy in prediabetes. Diabetes/metabolism research and reviews, 2023. PubMed 37470302
- Stino AM et al. Peripheral neuropathy in prediabetes and the metabolic syndrome. Journal of diabetes investigation, 2017. PubMed 28267267
- Thaisetthawatkul P et al. Prediabetes, diabetes, metabolic syndrome, and small fiber neuropathy. Muscle & nerve, 2020. PubMed 32012301
- Elafros MA et al. Towards prevention of diabetic peripheral neuropathy: clinical presentation, pathogenesis, and new treatments. The Lancet. Neurology, 2022. PubMed 36115364
Hurt in an accident? Start here.
You do not need a lawyer, a police report or a referral to be seen. Bring your symptoms and we will work out the rest.
Monday–Friday, 8:00 a.m. – 4:00 p.m. Same-day appointments are often available for new accident and injury patients.