HbA1c Test

What this test actually measures

Glucose is sticky. That is the whole mechanism, and it is worth understanding because it explains both what this test is good at and where it goes wrong.

When glucose circulates in your blood, some of it attaches to the hemoglobin inside your red blood cells. That attachment is essentially permanent for the life of the cell, and red cells live around 120 days.

So if you measure what proportion of your hemoglobin carries attached glucose, you get a record of how much glucose those cells have been swimming in over their lifetime. Higher average blood sugar means more attachment.

That is why no fasting is required. You are not measuring what your blood sugar is right now, you are reading an accumulated record. Breakfast cannot change it.

It also explains the weighting. Because red cells are constantly being replaced, the most recent weeks contribute more than the oldest ones, so an HbA1c leans toward the last month or so rather than weighting all three equally.

What the number means, and when it lies

The thresholds are diagnostic rather than statistical, set deliberately by guideline committees. Below 5.7 percent is normal, 5.7 to 6.4 is prediabetes, and 6.5 or above meets the threshold for diabetes.

Most root-cause practitioners aim lower than 5.7, generally around 5.0 to 5.4, on the reasoning that risk relates to blood sugar continuously rather than switching on at a cutoff. Someone at 5.6 and someone at 5.0 have been on different trajectories, and both reports say normal.

Now the part that matters more than the thresholds, because it is where this test genuinely misleads.

HbA1c depends on red blood cells living a normal lifespan. Anything that changes that changes the result without changing your blood sugar at all.

A 2020 review in Canadian Family Physician worked through these limitations directly. Conditions that shorten red cell survival, including haemolytic anaemia and some haemoglobin variants, cause HbA1c to read falsely low, because cells are being replaced before they accumulate their share of glucose. Iron deficiency anaemia tends to push it the other way, falsely high, since cells persist longer.

Kidney disease, recent blood transfusion, pregnancy and certain ethnic differences in haemoglobin all affect it too.

So the practical rule is that HbA1c is an excellent test in someone with normal red cells and a genuinely unreliable one in someone without. If your complete blood count or your ferritin is abnormal, interpret your HbA1c with that in mind rather than at face value.

The other limit is timing rather than accuracy. HbA1c reflects glucose, and glucose is the late signal. Insulin rises for years beforehand to hold glucose normal, which is why fasting insulin answers an earlier question from the same draw.

Test details

What is measured: glycated hemoglobin, reported as a percentage.

Sample: blood draw.

Provider: Quest Diagnostics, ordered through Jess's practitioner dispensary.

Fasting: not required, which is one of its practical advantages. It measures an average rather than a moment.

Turnaround: results typically within a few business days of the sample reaching the lab.

Order this test.

How the pricing works

I want to be straightforward about this, because lab pricing in the wellness industry frequently is not.

Jess takes no markup on the test itself. The lab cost is passed through exactly as it comes. What you pay is the test cost, the dispensary's service fee, the authorization fee, the collection fee where one applies, a flat handling fee for placing and managing the order, and the card processing cost. The handling fee is the part that is Jess's, and it is flat regardless of how expensive the test is.

That structure is deliberate. A percentage markup on labs creates an incentive to recommend expensive tests, and this way there is not one.

Because every blood test in one order shares a single draw fee, adding a second or third test to the same order costs considerably less than ordering them separately. The full lab menu shows what shares a draw with this one, and the order page itemises every fee before you pay.

Who this test is worth running for

Anyone who has never had it measured, and anyone with a family history of type 2 diabetes, excess weight around the middle, high blood pressure, polycystic ovary syndrome, or a history of gestational diabetes.

It is also worth running for anyone whose symptoms have a metabolic shape: an afternoon crash that arrives ninety minutes after eating, persistent sugar cravings, weight that will not move despite genuine effort, or unusual thirst and urination.

Most usefully, run it alongside fasting insulin rather than instead of it. A 2026 systematic review of 40 studies found that combinations of tests predicted progression to diabetes considerably better than any single one, with the combination of impaired fasting glucose, impaired glucose tolerance and an HbA1c of 6.0 to 6.4 carrying the highest annual incidence at 15.2 percent. More doors open means more risk, and one test only checks one door.

Ordering restrictions

The lab network cannot issue orders to residents of New York, New Jersey, Rhode Island, or Hawaii. New York, New Jersey, and Rhode Island prohibit direct-to-consumer lab testing outright, requiring a treating provider's signature on every requisition. Hawaii is excluded by the network. This is tied to where you live, not where the sample is collected, so it applies to kits as well as draws.

If you live in one of those four states, your doctor can order the same test.

What to do with the result

If it comes back at or above 6.5, that is a diagnostic threshold and it belongs with a doctor promptly rather than with a diet plan. It generally needs confirming on a second test.

If it lands in the 5.7 to 6.4 band, that is where the most useful work happens, and the progression research says what you do next genuinely matters. Resistance training, walking after meals, and reducing refined carbohydrate are the levers with the most consistent effect.

If it is normal but you have symptoms, add fasting insulin. A normal HbA1c means your blood sugar is currently being held steady, and it says nothing about the effort being spent to hold it.

If your blood count or iron studies are abnormal, read this result with caution and mention it to your provider, since red cell lifespan changes the number independently of your glucose.

Retest at about three months after any change, which matches the biology rather than testing sooner and reading noise.