Ramadan Fasting Linked to Gestational Diabetes Overdiagnosis: What the Research Shows

Ramadan Fasting Linked to Gestational Diabetes Overdiagnosis: What the Research Shows

A large health-records study in Spain checked 35,054 pregnancies for gestational diabetes. Women from Muslim-majority countries were diagnosed almost twice as often during Ramadan as at other times — about 13 in 100, versus about 9 in 100. Women from other backgrounds showed no change. Researchers think fasting, or how tests are timed around it, may explain the pattern.

Medical disclaimer: This article summarises published research for informational purposes only. It is not medical advice and is not a substitute for guidance from a qualified health professional. Always consult your doctor before starting any fasting protocol, especially if you have an existing health condition or take medication.

The Short Version

• What they tested: Whether Ramadan fasting changes how often pregnant women get diagnosed with gestational diabetes.
• Who did it: M. Carrasco and team at University Hospital Arnau de Vilanova, published in BMC Medicine in 2026.
• How many people: 35,054 pregnancies, all women, aged 18 to 50.
• How long: Health records from 2010 to 2019, ten years of data.
• What happened: Diagnosis rates almost doubled for these women during Ramadan — about 13 in 100, versus 9 in 100 otherwise.
• Read the study yourself: BMC Medicine 2026 →

What They Wanted to Find Out

Many Muslim women fast from sunrise to sunset every day during Ramadan. Some do this even while pregnant. Doctors did not know if this yearly fasting month changes how often gestational diabetes gets diagnosed. Gestational diabetes is high blood sugar that starts during pregnancy.

Researchers in Spain wanted to see if diagnosis rates shift during Ramadan. This matters because over-diagnosis can mean extra tests and worry a woman may not need. You can also read about fasting and women's hormones or fasting and ovarian reserve.

Who Was in the Study

Who they were: All participants were pregnant women aged 18 to 50. None had diabetes before pregnancy. One group came from countries where Islam is the main religion. Together, there were 35,054 pregnancies screened over ten years.

What the fasting actually looked like: Ramadan fasting means no food or drink from sunrise to sunset, for about a month each year. The researchers did not track who actually fasted. They used country of origin as a stand-in for Ramadan practice. This is one of the study's biggest limits.

What Happened

Women from Muslim-majority countries were diagnosed with gestational diabetes far more often during Ramadan.

• In the comparison group, diagnosis rates barely moved between Ramadan and other times.
• In women from Muslim-majority countries, the rate rose by close to half during Ramadan.
• The result held up even after researchers accounted for age, weight, number of pregnancies, and income.
• Researchers compared actual glucose test results, not just diagnosis labels, between the two time periods.

What Did Not Change

• Diagnosis rates in the comparison group stayed about the same, with or without Ramadan.
• The study did not measure weight, body fat, or muscle — it only looked at diabetes test results.

What the Researchers Said

The researchers said higher diagnosis rates during Ramadan may come from fasting itself, or from how and when tests get scheduled. They suggested doctors think carefully about testing timing during Ramadan.

What This Means for You

• If you are pregnant and fast: Talk to your doctor before Ramadan about when to schedule your diabetes test.
• Timing may matter: This study suggests when you get tested — not just fasting — can affect your result.
• For women specifically: Women from Muslim-majority countries in this study were almost twice as likely to get a diagnosis during Ramadan.
• It is not proof fasting causes diabetes: The study could not show that fasting itself raised blood sugar.
• Check your own numbers: Ask your doctor to explain your actual glucose readings, not just the label.
• Read more on fasting and women's hormones: see what fasting does to ovarian reserve and fasting and PCOS.

What This Study Could Not Tell Us

• It could not confirm which women actually fasted — it only used their home country as a guess.
• It only covered women in one region of Spain, called Catalonia.
• It ran on health records from 2010 to 2019, so it cannot say what happens today.
• It could not explain why diagnosis rates changed — only that they did.
• The abstract does not report who funded the study.

The Study Details

Carrasco, M., Vlacho, B., Franch-Nadal, J., Real, J., Monroy, G., Soldevila, B., et al. (2026). Overdiagnosis of gestational diabetes mellitus during Ramadan: a retrospective population-based study in Catalonia, Spain. BMC Medicine. PMID: 41559733

Common Questions

Does fasting during Ramadan cause gestational diabetes?

This study cannot answer that. It only found more diagnoses during Ramadan, not proof fasting raises blood sugar. Test timing could explain part of the pattern.

Is intermittent fasting safe during pregnancy?

This study did not test that question directly. It only looked at diabetes test results, not safety overall. Always ask your own doctor before fasting while pregnant.

Why were gestational diabetes rates higher during Ramadan in this study?

The researchers are not sure. They think it may be fasting itself, or simply how and when tests get scheduled around Ramadan.

Did fasting affect all pregnant women in the study the same way?

No. Only women from Muslim-majority countries showed higher diagnosis rates during Ramadan. The comparison group showed almost no change.

How many women were in this study?

The study used health records from 35,054 pregnancies in Catalonia, Spain. It covered ten years, from 2010 to 2019.

More Research Like This

• Does time-restricted eating change women's hormones?
• Intermittent fasting and ovarian reserve in women
• Intermittent fasting improved menstrual regularity in PCOS
• Two-day fasting cycles and iron levels in women
• Ramadan fasting and gut bacteria
• Ramadan fasting and blood pressure, cholesterol, blood sugar
• Ramadan fasting and insulin response in healthy men

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