This article describes possible interactions with metformin oral tablet. Interactions can cause a drug to have a different effect on the body than expected. Interactions can occur due to medications, alcohol, or certain health conditions.
Metformin comes as tablets and extended-release tablets that you swallow. (“Extended release” means the drug slowly releases into your body over time.)
Boxed warning: Risk of lactic acidosis
Metformin has a boxed warning for the risk of lactic acidosis. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
See the end of this article for more information about this warning.
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Other drugs and metformin
The drugs in the list below may interact with metformin oral tablet. This article doesn’t include all drugs that may interact with metformin.
Drug classes or drugs that may interact with metformin oral tablet include:
Metformin oral tablet may also interact with insulin drugs, such as insulin glargine (Basaglar), and sulfonylureas (another class of medications used to treat type 2 diabetes), such as glipizide (Glucotrol XL). When taken with metformin, these drugs can increase the risk of low blood sugar as a side effect of metformin or the sulfonylurea or insulin drug.
But for some people, taking two different classes of medications to help manage their type 2 diabetes may be appropriate. Talk with your doctor if you have questions about your medications and potential interactions.
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When to avoid metformin
Certain health conditions or other factors could increase some risks with metformin oral tablet. Because of this, doctors may not prescribe metformin in these cases. These warnings about health conditions or other factors are called contraindications.
Here’s a list of contraindications for metformin oral tablet:
- Severely decreased kidney function: If you have severely decreased kidney function, you’re at higher risk of lactic acidosis from taking metformin oral tablet. Your doctor may order diagnostic tests to check your kidney function before prescribing metformin.
- Metabolic acidosis: If you have metabolic acidosis, taking metformin oral tablet may worsen your condition. Metformin has a boxed warning regarding the risk of lactic acidosis (a form of metabolic acidosis) as a side effect. See the end of this article for more information about this warning.
- Past allergic reaction to metformin: If you’ve ever had an allergic reaction to metformin oral tablet, taking it again may cause another allergic reaction.
Before you start taking metformin, tell your doctor if anything listed above relates to you. They can recommend whether you should take metformin.
Alcohol and metformin
Metformin oral tablet is known to interact with alcohol. It’s best to minimize or avoid drinking alcohol while taking metformin.
Taking metformin oral tablet and drinking alcohol, especially in large quantities, increases the risk of lactic acidosis. Metformin has a boxed warning regarding this risk. (See the end of this article to learn more about this warning.)
If you drink alcohol and have concerns about avoiding it or minimizing consumption while taking metformin oral tablet, talk with your doctor.
Other interactions and metformin
Interactions can occur with foods, supplements, vaccines, and some lab tests. Below, you can learn whether metformin oral tablet has these interactions.
The following information doesn’t include all other possible interactions with metformin.
Metformin interactions with food
Metformin can interact with green tea, which can lower blood glucose levels. This combination could cause low blood sugar, although the risk doesn’t appear to be high.
Because of possible metformin interactions with food, talk with your doctor or pharmacist about foods you should avoid while taking metformin oral tablet.
Note: While metformin can interact with garlic supplements (see below), it’s not expected to interact with garlic used in cooking and foods.
Metformin and supplements
Before taking metformin oral tablet, tell your doctor and pharmacist about any herbs you take, as well as vitamins and supplements. Doing so may help you avoid interactions.
In addition to the interactions discussed below, metformin may interact with garlic supplements. Garlic supplements may lower blood glucose. Using this combination could raise your risk of low blood sugar as a side effect. Your doctor may prescribe a lower dosage of metformin oral tablet if you take a garlic supplement.
If you have questions about other possible supplement interactions that may affect you, talk with your doctor or pharmacist.
Metformin interactions with herbs
Metformin oral tablet isn’t known to interact with any herbs. But this doesn’t mean interactions with herbs can’t happen or won’t be identified later.
Because of this, ask your doctor or pharmacist before taking any herbs or herbal products while taking metformin oral tablet.
Metformin interactions with vitamins and minerals
Metformin oral tablet may interact with chromium supplements. This mineral is often used for improving how well insulin made by your body works.
Chromium supplements may lower blood glucose. Taking this combination could increase the risk of low blood sugar as a side effect. Your doctor may prescribe a lower dosage of metformin if you take a chromium supplement.
Because of this, talk with your doctor or pharmacist before taking chromium supplements while taking metformin oral tablet. Also, ask what other vitamins should not be taken with metformin.
Metformin and vaccines
Metformin oral tablet isn’t known to interact with any vaccines. But this doesn’t mean interactions with vaccines can’t happen or won’t be identified later.
Because of this, talk with your doctor or pharmacist before receiving any vaccines while taking metformin oral tablet.
Metformin and lab tests
Metformin oral tablet isn’t known to interact with lab tests. But this doesn’t mean interactions with lab tests can’t happen or won’t be identified later.
Because of this, talk with your doctor or pharmacist before having any lab tests performed while taking metformin oral tablet.
Metformin and cannabis or CBD
Metformin oral tablet isn’t known to interact with cannabis (commonly called marijuana) or cannabis products such as cannabidiol (CBD). But this doesn’t mean interactions can’t happen or won’t be identified later.
As with any drug or supplement, talk with your doctor before taking cannabis with metformin.
Note: Cannabis is illegal at a federal level but is legal in many states to varying degrees.
Health factors and metformin
Certain medical conditions or other health factors may increase the risk of interactions with metformin oral tablet. Keep in mind that interactions could lead to side effects or affect how well metformin works. Before taking metformin oral tablet, tell your doctor about your health history. They’ll determine whether metformin is right for you.
These health conditions or other factors might interact with metformin oral tablet:
Questions about metformin and interactions
Here you’ll find answers to some common questions about metformin and possible interactions.
Does metformin have interactions with ibuprofen?
No, metformin isn’t known to interact with ibuprofen. But certain side effects of ibuprofen could cause an interaction with metformin.
Specifically, ibuprofen can cause a decrease in how well your kidneys work. Your body relies on your kidneys to get rid of metformin. Levels of metformin can increase and raise the risk of side effects, including lactic acidosis,* if your kidneys aren’t working at full capacity.
Metformin and ibuprofen don’t usually interact. But if you develop kidney-related side effects from taking ibuprofen, this could raise your risk of side effects from taking metformin. Your doctor can recommend ways to monitor your kidney function, such as having periodic blood tests during treatment.
* Metformin has a boxed warning regarding the risk of lactic acidosis. See the end of this article to learn more about this warning.
What vitamins or supplements should not be taken with metformin?
You can take metformin and vitamins at the same time, but some supplements should be avoided when taking metformin.
For example, metformin may interact with chromium supplements. Chromium is a mineral that may be used to help insulin made by your body work.
Chromium supplements may lower blood glucose. Metformin also lowers blood glucose. Taking this combination could increase your risk of low blood sugar as a side effect.
This doesn’t mean you should not take chromium supplements and metformin together, but you should check with your doctor before doing so. Depending on your health and treatment goals, your doctor may prescribe a lower metformin dose if you take a chromium supplement while taking metformin oral tablet. But they may also recommend not taking chromium supplements together with metformin.
Besides chromium, there aren’t other supplements reported to interact with metformin. But this doesn’t mean metformin interactions with other supplements and vitamins don’t exist. Talk with your doctor for more information.
Preventing metformin interactions
You may be able to help avoid certain interactions with metformin oral tablet. Before taking this drug, discuss possible interactions with your doctor and pharmacist.
Things to consider include:
- Whether you drink alcohol or use cannabis.
- Other medications and herbs you take, as well as vitamins and supplements. Your doctor or pharmacist can help you fill out a medication list.
- What to do if you’re prescribed a new drug while taking metformin oral tablet.
Taking metformin exactly as your doctor prescribes can also help prevent interactions.
What to ask your doctor
If you have questions about metformin and possible interactions, talk with your doctor.
Questions you may want to ask your doctor include:
- Does my risk of interactions depend on my dosage of metformin?
- If I take metformin and have certain health conditions, will you monitor me more closely during treatment?
- If I take insulin and I’m prescribed metformin, should I be prescribed a lower insulin dosage?
- Should I let you know if I make lifestyle changes, such as changes to my diet or exercise routine? Can this affect my risk of lactic acidosis?
Boxed warning for metformin
Metformin has a boxed warning for the risk of lactic acidosis. A boxed warning is the most serious warning from the FDA.
In rare cases, metformin can cause lactic acidosis. This side effect didn’t occur in studies of metformin, but has happened since the drug was approved for use. Lactic acidosis can be life threatening in extreme cases.
With lactic acidosis, too much lactic acid builds up in your system. Symptoms can include:
- a fruity scent on your breath
- excessive thirst
- confusion
- exhaustion
- cramps or pains in your muscles
Certain factors increase the risk of lactic acidosis from taking metformin. These factors include:
- kidney problems, such as chronic kidney disease
- liver problems, such as cirrhosis
- taking certain other medications with metformin, such as acetazolamide and other carbonic anhydrase inhibitors
- being age 65 years or older
- undergoing certain surgeries, procedures, or diagnostic tests
- drinking an excessive amount of alcohol while taking metformin
- experiencing certain health events while taking metformin, such as having a heart attack
To learn more, talk with your doctor.
Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
