Why we measure it

HbA1c is the clinical standard for diagnosing and monitoring disorders of glucose metabolism — prediabetes, type 1 diabetes, and type 2 diabetes. It captures what a fasting glucose reading cannot: sustained hyperglycaemia across weeks and months, which is the form of glucose exposure that drives tissue damage. Long-term elevation drives the microvascular complications of diabetes — retinopathy, nephropathy, and peripheral neuropathy — through a mechanism of glycation and oxidative stress. The landmark DCCT trial in type 1 diabetes and the UKPDS in type 2 diabetes both demonstrated that reducing HbA1c lowers the incidence and rate of progression of these complications. Beyond diabetes, HbA1c carries clinical significance in people without a diagnosis. A large prospective analysis published in the New England Journal of Medicine (Selvin et al., 2010) demonstrated that HbA1c in the prediabetic range independently predicts cardiovascular disease, coronary heart disease, and stroke in non-diabetic adults — establishing it as a cardiovascular risk marker, not only a glycaemic one.

Why every 3 months

The biology of the test and the quarterly draw cadence are precisely aligned. HbA1c reflects the previous 90 days — the lifespan of a red blood cell. Each quarterly reading therefore captures a full, non-overlapping window of glycaemic exposure since the last draw. Testing more frequently adds noise because consecutive readings overlap. Testing annually leaves nine months of glycaemic drift unobserved. Quarterly is the minimum resolution at which the test is meaningful as a trend tool — which is why Pulse, the quarterly backbone of the protocol, includes it at every draw.

What movement means

The American Diabetes Association classifies HbA1c into three ranges in its Standards of Medical Care in Diabetes, updated annually. These are classifications defined by the ADA — not by Nexuses. Below 5.7% is classified as normal, with no evidence of prediabetes or diabetes. Between 5.7% and 6.4% is classified as prediabetes — impaired glucose regulation that significantly increases the risk of progressing to type 2 diabetes, and that carries independent cardiovascular risk independent of a formal diabetes diagnosis. At 6.5% or above, the ADA classifies the finding as consistent with a diabetes diagnosis, requiring confirmation by repeat testing in the absence of clear hyperglycaemic symptoms. For individuals already diagnosed with diabetes, the ADA recommends an HbA1c target below 7.0% for most adults, with individualisation based on clinical context.

In the protocol