Hyperglycemia (High Blood Sugar)

Hyperglycemia (also known as high blood sugar or high blood glucose) happens when there is too much sugar, or glucose, in your blood. This condition is common in people with diabetes, but there can be other causes, including medicines used to treat breast cancer. Hyperglycemia is a known side effect of:

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  inavolisib (brand name: Itovebi)

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  Piqray (chemical name: alpelisib)

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  Truqap (chemical name: capivasertib)

Blood glucose is your body’s main source of energy. The glucose comes from the foods you eat. Your body breaks down food into glucose and releases it into the bloodstream. When blood glucose goes up, it tells your pancreas to release the hormone insulin. Insulin helps glucose get into your cells so they can use it for energy.

But if your pancreas doesn’t make enough insulin or if your body can’t use insulin properly, your blood glucose levels stay high because the glucose isn’t moving into your cells.

If left untreated, high blood glucose can damage your nerves, eyes, kidneys, and heart. It can also lead to a sudden life-threatening condition known as a diabetic coma or  ketoacidosis. 

Symptoms of hyperglycemia include:

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  being thirsty all the time 

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  feeling unusually tired or weak

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  headache

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  needing to urinate often

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  blurred vision

Though not a common side effect of breast cancer treatment, hyperglycemia can be a side effect of Piqray and Truqap. Both medicines block how insulin works in the body, which leads to higher blood glucose levels.

Truqap, a targeted therapy used in combination with Faslodex (chemical name: fulvestrant), is used to treat locally advanced or metastatic, hormone receptor-positive, HER2-negative breast cancer with a PIK3CA, AKT1, or PTEN genetic mutation.

Truqap has not been tested in people with diabetes who need to take insulin. If you take insulin for diabetes and have been diagnosed with metastatic breast cancer that may respond to Truqap, you and your doctor will have to carefully weigh the risks and benefits of the medicine.

Piqray, another targeted therapy used in combination with Faslodex to treat advanced-stage or metastatic, hormone receptor-positive, HER2-negative breast cancer with a PIK3CA mutation that has grown after hormonal therapy treatment.

Piqray also has not been tested in people with diabetes who need to take insulin.

If you’re prescribed Truqap or Piqray, your doctor should test your fasting blood sugar level before you start taking either medicine and monitor your blood sugar levels while you’re taking Truqap or Piqray. If you have any symptoms of hyperglycemia, call your healthcare team immediately.

If you have hyperglycemia, your doctor may recommend you pause Truqap or Piqray treatment, reduce the dose, or stop treatment altogether. Your doctor may prescribe another medication called metformin to help you control your blood sugar if you decide to resume Truqap or Piqray at a lower dose. 

If you have diabetes, haven’t been diagnosed with breast cancer, and often have hyperglycemia, your medical team may make changes to your eating plan, your exercise plan, or your diabetes medicines.