HbA1c: the three month window into your blood sugar, and how much you are actually risking.
A fasting glucose test tells you about this morning. HbA1c tells you about the last three months. The difference is enormous.
A fasting glucose test tells you how your blood sugar is doing this morning. It is useful, but it is like checking the weather by looking out the window for five seconds. HbA1c tells you what the weather has been like for the past three months.
HbA1c (glycated haemoglobin) measures the percentage of red blood cells that have had glucose bonded to them. Because red blood cells live for approximately 90 to 120 days, the reading reflects your average blood sugar over that entire window. It is one of the most reliable predictors of metabolic health we have.
The problem with "prediabetes" as a category.
Italian labs typically flag HbA1c as abnormal above 6.5% (diabetes threshold) or above 5.7 to 6.4% (prediabetes). But the relationship between blood sugar and risk is not a cliff. It is a slope.
A landmark study published in The Lancet established that people with HbA1c between 5.5% and 6.5%, technically prediabetic or even "normal", had significantly elevated cardiovascular risk. An HbA1c of 5.9% was associated with almost double the relative risk of a major cardiovascular event compared to 5.0%.
Prediabetes doesn't feel like anything. It doesn't hurt. It doesn't show up on an annual checkup. And it is reversible, but only if you know it is there.
What drives HbA1c up.
- High glycaemic index carbohydrates: white bread, pasta, rice, sugary drinks.
- Sedentary lifestyle. Muscle is the primary glucose sink; less muscle means less capacity to absorb sugar.
- Chronic sleep deprivation. Even one week of under sleeping raises insulin resistance significantly.
- Chronic stress. Cortisol directly raises blood glucose as part of the stress response.
- Low magnesium. It is a cofactor in insulin receptor function; deficiency impairs glucose uptake.
The most important thing about HbA1c is that elevations between 5.5% and 6.4% are almost entirely reversible with targeted lifestyle intervention. By the time you need medication, a decade of silent risk has already been accumulating.
What optimal looks like.
The lab threshold for normal HbA1c is below 5.7%. The research target for minimal cardiovascular risk is below 5.4%. Most Rosa members who test in the 5.4 to 5.7% range have room to improve, and usually want to know exactly how.
