If you have type 2 diabetes you’ve likely heard of or are taking metformin to help manage your blood sugar.
All prescription medications come with potential side effects and might interact with other drugs or certain foods.
Certain medications interact with grapefruit and grapefruit juice, but is metformin one of them? Keep reading to find out.
What is metformin?
Metformin is one of the most commonly prescribed types of medication for type 2 diabetes. Metformin is the generic name of the medication and the brand name is Glucophage.
One of the benefits of metformin is that it doesn’t cause low blood sugar (hypoglycemia). Because it doesn’t cause low blood sugar, people with type 2 diabetes can take metformin along with other types of diabetes medication like sulfonylureas and injectable insulin.
Metformin is in a drug class called biguanides. Biguanides help reduce the amount of sugar your liver makes while improving insulin sensitivity, which helps reduce high blood sugar. There are two types of metformin – regular and extended-release (XR).
The common dosage for metformin ranges from 500 milligrams to a maximum of 2,550 milligrams per day. It’s usually recommended to split the dose among meals, typically three times per day.
Like with all prescription medications, metformin can lead to some side effects. The most common metformin side effects you may experience are heartburn, stomach pain, nausea or vomiting, bloating, gas, diarrhea, constipation, weight loss, headache, metallic taste in your mouth.
However, if levels of metformin increase in your blood it can cause a very rare but serious condition called lactic acidosis.
Metformin overdose is the main risk factor for developing lactic acidosis. According to a position statement in the American Diabetes Association’s Diabetes Care, “When metformin is used as labeled, the increased risk of lactic acidosis is either zero or so close to zero that it cannot be factored into ordinary clinical decision making.”
If you have severe renal impairment or kidney disease you might also be at greater risk of developing lactic acidosis because your kidneys can’t clear the lactic acid from your system.
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How grapefruit can affect some medications
Grapefruit and grapefruit juice contain chemicals called furanocoumarins. Furanocoumarins disrupt an enzyme called CYP (cytochrome P450) in the small intestine which helps metabolize and clear the medication from your bloodstream.
When the action of this type of enzyme is impacted the drug is broken down more slowly, increasing the levels of the medication in your bloodstream. This means that the side effects of certain prescription medications can be enhanced if you consume grapefruit or grapefruit juice.
More than 85 drugs are known to interact with grapefruit. Grapefruit and grapefruit juice most commonly interact with medications for high cholesterol, blood pressure medications, and certain medications that treat mood disorders.
Find Out More About What Medications Grapefruit Can Interact With.
Is it safe to consume grapefruit while taking metformin?
Metformin has few potential food and drug interactions. Metformin isn’t on the common list of medications that clearly interact with grapefruit and grapefruit juice.
However, there are some studies that show a potential interaction between metformin and grapefruit.
In a small animal study, rats who were given grapefruit juice and metformin had higher levels of lactic acid compared to rats not given grapefruit juice. Levels of metformin were also higher in the livers of rats given grapefruit juice.
Researchers then concluded that drinking grapefruit juice might lead to a higher risk of lactic acidosis in patients taking metformin.
This study was on non-diabetic rats and not in humans, so more research would need to be done to determine if there is a potential risk for humans taking metformin and grapefruit.
Due to a lack of evidence that metformin and grapefruit negatively interact in humans with type 2 diabetes, it’s considered safe to take both metformin and grapefruit. However, if you have any concerns you should consult your healthcare provider and/or pharmacist.
The effects of grapefruit on diabetes mellitus
Grapefruit contains carbohydrates in the form of natural sugars like most other fruits. One-half of a grapefruit contains around 13 grams of carbohydrates, two of those being from dietary fiber.
Fiber doesn’t raise your blood sugar levels because your body can’t absorb it. Many people who monitor their carbohydrate intake to help manage their blood sugar levels choose to subtract the grams of fiber from the total carbohydrates since that’s the actual amount that will likely impact their blood sugar.
Grapefruit is rich in vitamin C, with one-half of a grapefruit providing over 60% of the daily recommended amount. According to a study, vitamin C may help promote improved blood sugar control.
Study participants receiving 1000 milligrams of supplemental vitamin C daily experienced significant reductions in fasting blood sugar, hemoglobin A1c, triglycerides, LDL cholesterol, and insulin levels compared to those taking lower doses of vitamin C (500 milligrams daily).
Another study found that grapefruit product consumption (fresh grapefruit or grapefruit capsules) resulted in more weight loss and less insulin resistance compared to participants who didn’t receive any grapefruit.
This could be relevant to people with type 2 diabetes who usually suffer from insulin resistance and are at higher body weights.
Grapefruit juice is higher in carbohydrates and sugars like all fruit juice. One cup of grapefruit juice contains 23 grams of carbohydrates which are primarily from natural sugars which is similar to the sugar content of orange juice.
If you have diabetes, it’s fine to include grapefruit and grapefruit juice in your diet in moderation. Grapefruit juice is higher in sugars so will raise your blood sugar more significantly than the whole grapefruit.
Alternatives to grapefruit and grapefruit juice
If you’d rather avoid the combination of metformin and grapefruit, other foods and juices rich in vitamin C include:
- Oranges and orange juice
- Strawberries
- Bell peppers
- Acerola cherries
- Kale
- Kiwis’
- Broccoli
- Brussels sprouts
Conclusion
Grapefruit and grapefruit juice interact with certain medications, causing levels of the medication to build up in your system.
If levels of metformin build up in your system, a rare but serious complication called lactic acidosis can occur.
Based on the current scientific evidence available, metformin and grapefruit aren’t thought to cause a drug interaction so it is considered safe to consume them together. Always consult your healthcare professional or pharmacist if you have questions about metformin and grapefruit, though.
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