Every 3 months, a number comes back from the lab and suddenly defines how your child’s diabetes management is going. The endocrinologist’s expression changes based on it. Parents feel pride if it’s low or shame if it’s high. Insulin doses get adjusted because of it.
The A1C test is genuinely useful. It is also a significantly imperfect measure that can be misleading — sometimes dangerously so. Understanding what it actually tells you, and what it doesn’t, makes you a better advocate for your child and a more realistic interpreter of what the quarterly visit results mean.
What A1C Actually Measures
Hemoglobin A1C (HbA1c, or just A1C) measures the percentage of hemoglobin — the protein in red blood cells that carries oxygen — that has glucose attached to it (glycated hemoglobin).
When blood sugar is elevated, glucose molecules bind to hemoglobin in a process called glycation. The higher the average blood sugar over time, the more hemoglobin becomes glycated. Since red blood cells live approximately 90–120 days, the A1C reflects average blood sugar over roughly the preceding 3 months — with more recent blood sugar weighted more heavily than older readings.
The conversion: A1C percentage maps approximately to average blood glucose as follows:
| A1C % | Estimated Average Blood Glucose |
|---|---|
| 6.0% | ~126 mg/dL (7.0 mmol/L) |
| 6.5% | ~140 mg/dL (7.8 mmol/L) |
| 7.0% | ~154 mg/dL (8.6 mmol/L) |
| 7.5% | ~169 mg/dL (9.4 mmol/L) |
| 8.0% | ~183 mg/dL (10.2 mmol/L) |
| 8.5% | ~197 mg/dL (10.9 mmol/L) |
| 9.0% | ~212 mg/dL (11.8 mmol/L) |
What the Target Numbers Are — and Why They’re Not the Same for Every Child
The ADA’s 2024 Standards of Care recommend an A1C below 7.0% for most children and adolescents with T1D — but with an explicit acknowledgment that this target must be individualized based on hypoglycemia risk, developmental stage, and family circumstances.
Critically, the ADA moved away from age-stratified targets (which used to recommend higher targets for young children) based on evidence that lower A1C is achievable and beneficial at all ages when CGM and modern insulin therapy are available — but that hypoglycemia risk must be weighed seriously.
Why targets are not the same for every child
A child with frequent severe hypoglycemia or hypoglycemia unawareness should not be targeting a very low A1C — the risk of severe lows outweighs the marginal benefit of a lower average.
A child with newly diagnosed T1D in the honeymoon phase may achieve a very low A1C easily. This doesn’t necessarily mean the management approach is producing that outcome — the residual pancreatic function is doing some of the work.
A child in active puberty will typically have a higher A1C than outside of puberty due to physiological insulin resistance that is partially irreducible. Comparing a 14-year-old’s A1C unfavorably to their 9-year-old result ignores the hormonal reality.
A child managing T1D with limited technology access (no CGM, basic insulin regimen) cannot reasonably be expected to achieve the same A1C as a child on a closed-loop system with 24/7 monitoring.
A result of 8.2% does not mean your child “failed” the past three months. It means their average blood sugar was approximately 188 mg/dL. That’s a starting point for analysis, not a grade. Shame about the number — directed at your child or yourself — is clinically counterproductive and not a useful response to data.
The Critical Limitation: A1C Hides Variability
This is what many parents and even some clinicians underappreciate: two children can have the same A1C and be in completely different metabolic situations.
Consider:
- Child A spends 70% of time in range (70–180 mg/dL), with mild fluctuations
- Child B spends equal time at 50 mg/dL and 300 mg/dL — constant severe lows and highs
Both may have an A1C of approximately 7.4%. Child A has excellent control. Child B has dangerous control. The A1C does not distinguish between them.
This is why Time-in-Range (TIR) has emerged as an equally important — and in many ways more clinically informative — measure of glycemic control.
Time-in-Range explained
TIR measures the percentage of time blood sugar stays within the target range (70–180 mg/dL). It requires CGM data to calculate. The ADA’s 2024 standards identify the following TIR targets for children:
| Metric | Target for Most Children |
|---|---|
| Time in range (70–180 mg/dL) | Above 70% |
| Time below range (<70 mg/dL) | Less than 4% |
| Time severely low (<54 mg/dL) | Less than 1% |
| Time above range (>180 mg/dL) | Less than 25% |
| Time severely high (>250 mg/dL) | Less than 5% |
A child with an A1C of 7.0% and a TIR of 60% with 8% time below range has a concerning control profile — the low average is being purchased with dangerous hypoglycemia. A child with an A1C of 7.3% and TIR of 74% with less than 2% below range has an excellent profile.
Ask your endocrinologist to review both metrics at every appointment. If your child uses a CGM, this data is available from Dexcom Clarity or LibreView and should be part of every quarterly review.
What Can Make A1C Artificially High or Low
Several conditions affect A1C independent of actual blood glucose control:
Conditions that artificially lower A1C (falsely reassuring):
- Iron deficiency anemia — reduced red blood cells means less hemoglobin to glycate, producing falsely low A1C
- Hemolytic anemia — red blood cells die faster, newer cells have less time to accumulate glycation
- Recent blood transfusion
- Certain hemoglobin variants (hemoglobin S, C, E — relevant in populations with higher rates of hemoglobinopathies)
Conditions that artificially raise A1C (falsely alarming):
- Iron, B12, or folate supplementation
- Dehydration
- Certain hemoglobin variants in opposite direction
If your child’s A1C doesn’t match their CGM data or logbook average, discuss the possibility of a condition affecting the test’s accuracy with your endocrinologist. A fructosamine test or Glycomark test can provide an alternative measure of glycemic control that isn’t affected by hemoglobin variation.
If your child uses a CGM, the ambulatory glucose profile (AGP) report from Dexcom Clarity or LibreView gives your endocrinologist far more actionable information than A1C alone — it shows patterns by time of day, variability metrics, and time in range. Generate a 90-day report before each appointment and email it ahead or bring a printout.
How to Have a Productive Conversation About A1C at the Appointment
Parents often feel either defensive or devastated about A1C results, which makes the appointment less clinically useful. Some reframes:
Instead of “What does this mean about how we’ve been managing?”
Ask: “What patterns in our data explain this result, and what’s the highest-yield adjustment to make?”
Instead of accepting “the A1C is too high, we need to tighten control”
Ask: “What specifically should we adjust, what’s the expected effect size, and what’s the timeline before we expect to see a change?”
Instead of silent nodding to a target you’re not sure is realistic
Ask: “Is this target appropriate given [current puberty stage / hypoglycemia history / available technology]? What target are we aiming for in the next 3 months specifically?”
If the A1C improved significantly:
Ask: “Is this improvement reflected in our TIR data? I want to make sure we’re not achieving a lower average through more lows.”
What the DCCT Tells Us About Long-Term A1C and Complications
The Diabetes Control and Complications Trial (DCCT) — the landmark study that established the relationship between glycemic control and diabetic complications — showed that every 1% reduction in A1C is associated with a 25–40% reduction in risk of microvascular complications (retinopathy, nephropathy, neuropathy).
This is the clinical foundation for treating A1C seriously. It matters.
But the DCCT also documented a significant increase in severe hypoglycemia in the intensive control group — which is why the goal is not the lowest possible A1C, but the lowest achievable A1C without unacceptable hypoglycemia risk.
The post-DCCT EDIC study followed participants for decades and showed that the benefits of earlier good control persisted even after some deterioration in management — the concept of metabolic memory. This means the management work done in childhood has long-term protective effects that persist even into adulthood. The work is worth doing. But it should be done in a way that is sustainable and safe.
When to Be Concerned About A1C Direction, Not Just Level
A single A1C result is less informative than the trend. Consider:
- An A1C of 8.0% that is down from 9.2% three months ago represents meaningful progress
- An A1C of 7.8% that is up from 6.9% three months ago represents a deteriorating trend worth investigating
- An A1C that is consistently between 7.5–8.0% despite seemingly appropriate management warrants a systematic review of possible barriers — equipment, adherence, undiagnosed celiac, insulin resistance, or psychosocial factors
Track your child’s A1C over time in a simple table or chart. The direction of travel often tells you more than any single value.