Will having Hashimoto's thyroiditis or celiac disease make my T1D harder to manage?

Based on this study, having an extra autoimmune condition did not significantly worsen blood sugar control. However, undiagnosed or untreated conditions could affect your health, so early detection and treatment remain important.

Why are women more likely to have multiple autoimmune conditions?

Women are generally more prone to autoimmune diseases than men, likely due to hormonal and immune system differences. This pattern was clearly seen in the study, with women having significantly higher rates of additional autoimmune diagnoses.

1 in 3 T1D Adults Have Another Autoimmune Disease

Key takeaways

✓Blood sugar control was similar whether or not patients had an extra autoimmune condition
✓CGM data confirmed HbA1c findings, adding reliability to the results
✓Large sample of 439 adults provides meaningful real-world insight

Quick specs

Journal	Endocrine
Year	2025
PMID	40663292

What This Study Found

Researchers in Portugal studied 439 adults living with type 1 diabetes (T1D) to find out how many also had other autoimmune conditions — and whether having those extra conditions made managing blood sugar harder.

Key Findings

About 1 in 3 people (33.8%) with T1D in this study had at least one other autoimmune disease. The most common were:

Hashimoto's thyroiditis (an underactive thyroid condition) — found in 28.8% of participants
Celiac disease — found in 3.9% of participants

Women were significantly more likely to have an additional autoimmune condition than men.

Did Extra Autoimmune Conditions Affect Blood Sugar Control?

Importantly, the answer appears to be no. The study compared blood sugar control between those with and without extra autoimmune diseases using two key measures:

HbA1c (a 3-month blood sugar average): nearly identical in both groups (7.7% vs. 7.8%)
Time in Range (hours spent with healthy glucose levels, measured by CGM): similar in both groups (58.7% vs. 56.6%)

This suggests that having an additional autoimmune condition does not necessarily make it harder to reach your blood sugar goals.

Why This Matters for You

If you have T1D, your immune system is already overactive — which means you are at higher risk for other autoimmune conditions. Many of these, like thyroid disease and celiac disease, can be managed effectively once diagnosed. The researchers recommend routine screening for autoimmune diseases in all adults with T1D, along with personalised care plans.

What Researchers Still Need to Learn

This was a snapshot study, meaning it looked at one point in time. Longer studies are needed to understand whether multiple autoimmune conditions might affect heart health or blood sugar management over many years.

References & Sources

Frequently asked questions

Yes. This study supports routine screening, especially for thyroid disease and celiac disease, which are the most common autoimmune conditions found alongside T1D. Ask your doctor about testing.

Editorial note

This article is for educational purposes only and does not constitute medical advice. Always consult your healthcare provider before making changes to your diabetes management. Last reviewed: July 16, 2026 by the MDS Diabetes editorial team.

What to do next

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1 in 3 Adults with T1D Also Have Another Autoimmune Condition