Can A Low Carb Diet Cause A False Negative Hba1c Test?

[Fergie01]

Hi everyone,

Sorry this is a bit long but I have a few questions.

I’ve been feeling quite run-down (tired and achy, can’t focus, constantly thirsty, headache, having to get up at night 5-10 times to urinate) for a good year or so now, although my symptoms have worsened in the last couple of months to the point that I’m really worried about how I’ll cope at school (starting year 13 (Upper 6th) in a fortnight, so the important A-level year).

Whenever I eat within half an hour I feel very headachy, tired and dizzy, irritable and I find it really hard to think and concentrate, as if I’ve taken a sleeping pill. This post-prandial fatigue state used to only bother me after something like a panini, a bowl of pasta or fruit juice, so I started a low carbohydrate/possibly ketogenic diet (carbs <50 g/day) a few months ago in the hope that I’d feel better. But in the last month or so it has started happening every time I eat. Plus even though I’ve increased my fat and protein intake I’ve lost a couple of kilograms which has clearly come from muscle, as you can see a difference in my triceps and quads and I feel weaker. I can’t win!

I have a GP appointment tomorrow to speak about this, and hopefully they’ll be willing to test my thyroid hormones, fasting glucose, c-peptide and HbA1C. Have I missed any other important tests that should be run to exclude the various causes of my symptoms? Does anyone know if a urine test for glucose would be positive if someone has LADA, and whether the result of that could be affected by a low carb diet?

Finally, as alluded to in the title, I was wondering if anyone is aware of whether having been on a low carbohydrate (thus high fat) diet for a few months could result in my HbA1C or fasting glucose result being low enough to not indicate diabetes type 1.5/LADA (I think this most closely matches my symptoms, but please let me know if you think otherwise!) even if I actually have the condition? I’m worried that the low carb diet will mask the signs of an underlying problem and mean that I have to spend longer feeling unwell before we work out why.

Additionally, can type 1.5 diabetes occur in adolescence and can it come on over a period of a year or two, as my symptoms have, without any significant event (e.g. ketoacidosis)? Or am I more likely getting myself anxious unnecessarily? Could I be suffering from reactive hypoglycaemia and if so, how is one tested and treated for that?

[PaulL]

The question is whether you are insulin-resistant or whether the β-cells in your Isles of Langerhans are being attacked by your immune system. In the latter case, there may not be much you can do to halt the destruction, but eating a ketogenic diet will help keep your serum glucose stable enough to avoid overdosing insulin once it is prescribed, and risking hypoglycaemic episodes. Most Type I diabetics who eat a ketogenic diet find that they are fine taking only their basic daily dose and dropping the bolus dose before each meal.

There are also indications, but I believe no proof, that a ketogenic diet can help regulate the immune system, but that may simply be a result of lowering insulin levels, and if your insulin level is already low from the destruction of β-cells, there may not be much help to be had from this avenue.

If your problem is insulin resistance, the treatment is not to supply insulin, but to avoid the need for it, and again, a well-formulated ketogenic diet is extremely helpful in this regard. Overdosing on serum glucose by eating carbohydrate in amounts typical of the standard Western diet is contraindicated under all possible circumstances.

HbA_1C is an indication of the degree of glycation of your haemoglobin. Since your red corpuscles last for up to ninety days, this is a relatively stable indicator, and unless your serum glucose has been consistently low for a long enough period, it is unlikely that your HbA_1C result will mislead your doctors. You should probably talk to your physician about what the diagnostic criteria are for distinguishing between Type 1.5 and Type II.

In any case, one of the benefits of keto-adaptation is enhanced brain clarity, resulting from switching the brain over from metabolising glucose to using β-hydroxybutyrate instead.

One last possibility to consider is that of sodium deficiency resulting from low carbohydrate intake. The amount of carbohydrate normally ingested in the standard Western diet inhibits the rate of excretion of sodium by the kidneys; in the absence of carbohydrate typical of a ketogenic diet, the kidneys return to their normal, higher rate of sodium excretion. While it appears that your symptoms are not primarily the result of sodium deficiency, lack of sodium may be exacerbating them. Aim for a total of 2-1/2 teaspoons of salt each day, including salt already present in food; this should eliminate any problem caused by low sodium, at least.

[PaulL]

P.S.—Good luck in school, and let us know periodically how you’re getting on, all right?