Blood sugar levels rise 14 times faster after starting antipsychotics, raising concerns over diabetes risk

Blood sugar levels rise 14 times faster after starting antipsychotics, raising concerns over diabetes risk

Regular monitoring can help patients receive the mental health benefits of antipsychotic medicines while reducing the risk of preventable physical health complications.

People starting antipsychotic medication may face rapid changes in blood sugar and weight during the first three months of treatment, raising concerns about their risk of developing type 2 diabetes.

Antipsychotic medicines treat mental health conditions such as schizophrenia and bipolar disorder by helping control symptoms, including hallucinations, delusions and severe mood changes. However, some can cause weight gain and raise blood sugar levels, increasing the risk of type 2 diabetes.

A study published in The Lancet Psychiatry found that the first 90 days after starting treatment were a critical period for metabolic changes. The study analysed health records of nearly 97,000 adults aged 18 to 59 in England who had severe mental illnesses and began taking antipsychotic medicines between 2000 and 2023.

The researchers examined patients' health records for two years before and two years after they started treatment, focusing on changes in weight and blood sugar levels.

They found that during the first 90 days of treatment, levels of HbA1c, a blood test that measures average blood sugar over about two to three months, rose around 14 times faster than before treatment began. Weight also increased around nine times faster.

The findings highlight the importance of monitoring patients early, as changes linked to diabetes risk may begin soon after treatment starts.

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The researchers found that changes in blood sugar and weight did not always occur together. This means a patient may experience rising blood sugar without significant weight gain, making it important for healthcare providers to monitor both measures rather than relying on weight alone.

The study examined four second-generation antipsychotic medicines: olanzapine, quetiapine, risperidone and aripiprazole. Of these, olanzapine was associated with the largest early increases in blood sugar and weight.

Among patients taking olanzapine, HbA1c levels rose around 50 times faster during the first 90 days than before treatment. Weight increased around 10 times faster over the same period.

These findings suggest that the type of medication may influence how a patient's body responds during the early stages of treatment. However, patients should not stop or change prescribed medication without consulting their healthcare provider.

The researchers said healthcare professionals should check patients' blood sugar and weight before treatment begins and continue monitoring them during the first few months.

Early checks can help identify concerning changes before they develop into more serious health problems. Where necessary, healthcare providers can offer advice on diet and physical activity, review treatment options or arrange further tests.

The study also found that patients who already had prediabetes when they started antipsychotic treatment were more likely to develop type 2 diabetes.

"Within two years, 19 per cent of patients who had prediabetes at the start of treatment developed type 2 diabetes. This compared with three per cent of those whose blood sugar levels were normal when they began taking the medicines."

According to the research, prediabetes occurs when blood sugar levels are higher than normal but not yet high enough to meet the criteria for diabetes. It indicates an increased risk of developing the condition, although progression is not inevitable.

The findings suggest that identifying patients with elevated blood sugar before they start treatment could help healthcare providers determine who needs closer monitoring.

Women also experienced greater increases in blood sugar and weight than men during the first 90 days of treatment.

Among women, HbA1c levels rose around 24 times faster, and weight increased around 12 times faster than before treatment. Among men, blood sugar levels rose around 10 times faster, while weight also increased around 10 times faster.

The reasons for these differences were not established by the study, but the findings underscore the importance of monitoring individual patients rather than assuming everyone will respond to medication in the same way.

People living with severe mental illnesses also face a higher burden of physical health problems, including cardiovascular and metabolic diseases. These conditions contribute to the gap in life expectancy between people with severe mental illnesses and the general population.

Some antipsychotic medicines may add to this burden through their effects on weight and blood sugar. This makes physical health monitoring an important part of mental healthcare.

The researchers said checking blood sugar and weight early could help doctors identify potential problems and provide support before more serious complications arise. Such monitoring may also help healthcare providers identify patients who need additional attention because of existing risk factors.

However, the study had limitations. It relied on information already recorded in general practitioner health records and could not account for every factor that might affect blood sugar and weight, including diet, exercise and other medications.

The findings do not mean that everyone taking antipsychotic medicines will develop diabetes. Instead, they show that the early months of treatment are an important period for monitoring metabolic health.

Regular monitoring can help patients receive the mental health benefits of antipsychotic medicines while reducing the risk of preventable physical health complications.

The World Health Organisation estimates that 23 million people worldwide live with schizophrenia, while about 36 million people were living with bipolar disorder in 2023. Globally, nearly 1.2 billion people were living with a mental disorder in 2023.