Understanding Type 1 Diabetes & Screening
T1D develops in stages long before symptoms show. A single blood test for islet autoantibodies can tell a family where they stand — years ahead of a crisis.
The three stages
Stage 1
Two or more islet autoantibodies present, blood glucose still normal. No symptoms — but the immune process has already started, and monitoring begins here.
Stage 2
Two or more autoantibodies plus dysglycaemia (abnormal glucose on OGTT or A1C). Still often symptom-free, and the window where early intervention matters most.
Stage 3
Clinical diagnosis: symptoms appear as insulin production falls. Screening ahead of this stage dramatically lowers the risk of presenting in DKA.
Screening for familial risk
First-degree relatives of someone with T1D carry roughly a 15x higher risk than the general population. Most new diagnoses still have no family history, so general-population screening is expanding too. Testing is a standard blood draw.
| Marker | What it means |
|---|---|
| GADA | Glutamic acid decarboxylase antibodies — the most common first marker in adults. |
| IA-2A | Insulinoma-associated-2 antibodies — often signals faster progression in children. |
| IAA | Insulin autoantibodies — typically the earliest marker in very young children. |
| ZnT8A | Zinc transporter 8 antibodies — adds sensitivity when other markers are borderline. |
Reading your result: one positive antibody usually means repeat testing later. Two or more means monitoring with your care team, since progression to Stage 3 becomes likely over time. A negative result at one point in life doesn't rule out a later change.
Signs and symptoms to know
- Unusual thirst and frequent urination
- Unexplained weight loss
- Persistent fatigue or irritability
- Blurred vision
- Fruity-smelling breath, nausea, or rapid breathing (urgent)
Clinical resources
Bring these to your next appointment:
- • ADA Standards of Care — screening and staging guidance
- • JDRF/Breakthrough T1D autoantibody screening programmes
- • TrialNet Pathway to Prevention relative screening
- • A printable question list for your endocrinology visit
Educational information only — always confirm testing and results with your clinician.