Here's a quiet thing that catches a lot of people off guard. If you have sickle cell trait (SCT) and your doctor uses an A1C blood test to screen for or manage diabetes, the result might not be telling the truth.
What the A1C is supposed to do. The A1C measures your average blood sugar over roughly the past three months. It's used to:
- Diagnose type 2 diabetes
- Diagnose prediabetes (where blood sugar is high but not yet in the diabetes range)
- Monitor how well diabetes treatment is working
A normal A1C is below 5.7%. Prediabetes is 5.7% to 6.4%. Diabetes is 6.5% or higher.
Why SCT throws a wrench into it. Most A1C testing methods rely on measuring slightly modified hemoglobin proteins. People with sickle cell trait carry a different kind of hemoglobin (HbS), and depending on which testing method your lab uses, the machine can read your A1C as falsely high or falsely low.
The consequences are real:
- Falsely high → you might be treated for diabetes you don't actually have, with side-effect-prone medications.
- Falsely low → you and your doctor might miss diabetes that is there, until complications show up.
What to do — three short asks at your next appointment:
1. "Doc, I have sickle cell trait. Is my A1C result reliable for that test method?" Your provider can call the lab. Some methods (HPLC, certain ion-exchange assays) are unaffected by HbS. Others give false readings.
2. "Can we use a different test to confirm?" Fasting glucose, oral glucose tolerance, fructosamine, glycated albumin, or continuous glucose monitoring all bypass the hemoglobin issue and can confirm what's really going on.
3. "Is my SCT noted in my chart?" If you can't remember whether your trait status is documented, ask. It should be in there permanently — it affects more than just diabetes testing.
For everyone — not just people with diabetes: This isn't only relevant if you've already been diagnosed. The A1C is also used to screen people for diabetes during routine physicals. If you have SCT, ask your provider whether the screening method is reliable, or use a fasting glucose instead.
The good news: there are accurate tests for everyone. You just have to ask.
— Dr. Rob
📄 Resource: CDC What You Should Know About Diabetes Tests if You Have Sickle Cell Trait.