For most people, taking a new medication may mean switching up your lifestyle a bit and that includes the foods you eat. A food-drug interaction means that a specific nutrient or compound within the food changes the way your body metabolizes the medication, and this can either enhance or reduce the dose your body gets, according to Johns Hopkins Medicine. The potential results: an increased risk of side effects, many of which can be dangerous, or the drug not working as it was intended.
Before introducing a medication, ask your pharmacist about any food interactions, including with alcohol, and any adjustments you may have to make to your diet. In this article, we will discuss metformin and the foods to avoid while taking it.
What is metformin?
Metformin, sold under the brand name Glucophage, among others, is the first-line medication for the treatment of type 2 diabetes, particularly in people who are overweight. It is also used in the treatment of polycystic ovary syndrome. It is not associated with weight gain and is taken by mouth.
Metformin is in a class of drugs called biguanides. Metformin helps to control the amount of glucose (sugar) in your blood. It decreases the amount of glucose you absorb from your food and the amount of glucose made by your liver. Metformin also increases your body’s response to insulin, a natural substance that controls the amount of glucose in the blood. Metformin is not used to treat type 1 diabetes (condition in which the body does not produce insulin and therefore cannot control the amount of sugar in the blood).
Metformin does not instantly reduce blood sugar levels. The effects are usually noticeable within 48 hours of taking the medication, and the most significant effects take 4–5 days to occur.
How should metformin be taken?
Metformin comes as a liquid, a tablet, and an extended-release (long-acting) tablet to take by mouth. The liquid is usually taken with meals one or two times a day. The regular tablet is usually taken with meals two or three times a day. The extended-release tablet is usually taken once daily with the evening meal. To help you remember to take metformin, take it around the same time(s) every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take metformin exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Swallow metformin extended-release tablets whole; do not split, chew, or crush them.
Your doctor may start you on a low dose of metformin and gradually increase your dose not more often than once every 1–2 weeks. You will need to monitor your blood sugar carefully so your doctor will be able to tell how well metformin is working.
Metformin controls diabetes but does not cure it. Continue to take metformin even if you feel well. Do not stop taking metformin without talking to your doctor.
Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.
Foods to avoid while taking metformin
Grapefruit and grapefruit juice: A 2009 paper found that there was an increase in the amount of lactic acid production in the rats that were exposed to grapefruit juice and metformin. Drinking grapefruit juice while taking metformin may lead to an increased risk of lactic acidosis in people taking metformin.
Alcohol: Avoid excessive alcohol intake (either short-term binge drinking or frequent consumption). Taking metformin with alcohol may increase the risk of a rare but serious and potentially life-threatening condition known as lactic acidosis, which is a buildup of lactic acid in the blood that can occasionally occur during treatment with metformin-containing products.
High fiber foods: High fiber foods can absorb metformin and lower their concentration in your bloodstream. If you eat large amounts of fiber, your metformin levels may decrease. Keep your fiber intake under 30 grams per day.
High-fat foods: Avoid foods high in trans and saturated fats when taking metformin. Fats can contribute to obesity, which increases the risk of developing type 2 diabetes. The researchers learned a key protein called Bcl10 is needed for the free fatty acids — which are found in high-fat food and stored in body fat — to impair insulin action and lead to abnormally high blood sugar.
High sodium foods: You should avoid food with too much sodium while you’re on metformin. Keep your sodium intake under 2300 milligrams per day. Although salt does not affect blood glucose levels, it’s important to limit the amount you eat as part of your diabetes management because too much salt can raise your blood pressure.
Processed carbs and sugar: while taking metformin, you still have to watch carbs and sugar—not just calories. Carbs and sugar provoke an insulin response that (among other things) tells your body to “Store fat now!” Insulin is a famine-protection hormone, designed to help you fatten up during the good times so you have a fat reserve when food is scarce. In our culture, for many of us, food is never scarce.
What drugs should I avoid while on metformin?
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
• Acetrizoic Acid
• Ethiodized Oil
• Iobenzamic Acid
• Iocarmic Acid
• Iocetamic Acid
• Iodohippuric Acid
• Iodoxamic Acid
• Ioglicic Acid
• Ioglycamic Acid
• Iopanoic Acid
• Iopronic Acid
• Ioseric Acid
• Iotroxic Acid
• Ioxitalamic Acid
• Metrizoic Acid
• Tyropanoate Sodium
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
• Thioctic Acid
Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
• Bitter Melon
• Guar Gum
• Methylene Blue
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Other Medical Problems
The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:
• Alcohol, excessive use or
• Underactive adrenal glands or
• Underactive pituitary gland or
• Undernourished condition or
• Weakened physical condition or
• Any other condition that causes low blood sugar—Patients with these conditions may be more likely to develop low blood sugar while taking metformin.
• Anemia (low levels of red blood cells) or
• Vitamin B12 deficiency—Use with caution. May make these conditions worse.
• Congestive heart failure, acute or unstable or
• Dehydration or
• Heart attack, acute or
• Hypoxemia (decreased oxygen in the blood) or
• Kidney disease or
• Liver disease or
• Sepsis (blood poisoning) or
• Shock (low blood pressure, blood circulation is poor)—A rare condition called lactic acidosis can occur. Talk with your doctor if you have concerns about this.
• Diabetic ketoacidosis (ketones in the blood) or
• Kidney disease, severe or
• Metabolic acidosis (extra acids in the blood) or
• Type 1 diabetes—Should not be used in patients with these conditions.
• Fever or
• Infection or
• Surgery or
• Trauma—These conditions may cause temporary problems with blood sugar control and your doctor may want to treat you with insulin.