Is Metformin Safe?

Metformin is a popular prescription drug that is used as a first-line treatment for prediabetes and type 2 diabetes. It is typically taken orally, in the form of a pill, once or twice each day. 

Metformin helps people manage their blood sugar levels. It reduces insulin resistance and has also been shown to help people lose weight. 

This article will investigate the safety profile of Metformin and its connections to diabetes. 

How does Metformin work?

Taken as a once or twice-daily oral pill, metformin is in a class of drugs called biguanides. These drugs are used to fight high blood sugar and are used most frequently for people with prediabetes, gestational diabetes, and type 2 diabetes. 

The drug lowers the amount of sugar produced by the liver, decreases sugar absorption in the intestines, and allows individual cells in the body to consume more sugar and use that sugar more efficiently.

Together, these three physiological changes decrease the amount of sugar (in the form of glucose) circulating in the blood.

As a result, the average person taking Metformin will see their HbA1c, the common measurement of blood sugar levels over time, decrease by about a percentage point, which translates into significantly lower blood sugar.

Who should not take Metformin?

It is important to know that not everyone should take Metformin. 

People with kidney problems should be careful in taking Metformin, and people with kidney problems who are over age 80 are generally advised not to take the drug.

People with liver disease and congestive heart failure may also be advised not to take Metformin.

Metformin has also not undergone rigorous clinical trials in pregnant and breastfeeding women or in children, although there is an evidence base to expect it would be effective. Nonetheless, use for these populations is generally approached with caution. 

The use of Metformin is not FDA-approved for people who have type 1 diabetes. While research indicates that Metformin may help increase insulin sensitivity in people with type 1 diabetes, it has not been established to help improve control or meaningfully improve other health outcomes.

Some people still take metformin for type 1 diabetes, primarily to help with weight loss.

Finally, some people can have an allergic reaction to Metformin, and so should not take the medication.

Similarly, people who have experienced a condition called metabolic acidosis while taking the drug will generally be advised not to take Metformin again. 

Because Metformin can also interact with numerous other prescription drugs, it is important to discuss any other prescriptions with your doctor or medical provider before getting a prescription.

What are the dangers of taking Metformin?

It is important to know that Metformin is generally considered a safe medication, but as with all drugs, it can have side effects and risks. 

Although rare, one of the most serious risks of taking Metformin is a condition called lactic acidosis, which involves a rapid buildup of lactic acid in the blood. 

Clinical research has established that lactic acidosis from Metformin is rare, occurring in only about 6 people per year out of every 100,000 people taking the drug, but the condition can be fatal if not treated promptly. 

Symptoms of lactic acidosis include abdominal pain, muscle cramps, difficulty breathing, and fatigue.

Another potential risk of taking metformin is that it can cause a decrease in vitamin B-12 levels.

Prolonged B-12 deficiency, which may also occur with anemia, can result in neurological problems, weakness, and fatigue. 

A study of 1,111 patients with type 2 diabetes found the risk is greatest in those who have been taking Metformin for more than 6 months and who were taking over 1,500 mg of the drug each day. 

B-12 supplementation and eating a healthy diet are both protective against this potential side effect. 

There are other, less dangerous side effects of Metformin, too. 

Among the most common side effects are:

• Bloating or excessive gas
• Stomach cramps
• Upset stomach
• Nausea and vomiting
• Diarrhea
• Hypoglycemia (low blood sugar levels)

Most of the gastrointestinal side effects will go away over time and can be eased or avoided completely if a person starts with a low dose and increases it over time

If side effects persist, or if any serious side effects occur, it’s important to discuss them with a doctor or other medical provider.

You can read our comprehensive guide to Metformin side effects for more information.

How long can you be on Metformin?

There is no established amount of time for how long a person can take metformin. Metformin is considered a long-term medication for the management of prediabetes and type 2 diabetes. 

However, Metformin’s effectiveness in regulating blood sugar levels may slightly decrease over time. Because of this, a medical care team may recommend that people who are on the drug for many years increase their dosage occasionally.

Metformin therapy is individualized to each person and the long-term treatment plan depends on the person’s response and the goals of treatment, as well as whether or not they experience any adverse effects from the drug.

Metformin is also useful because it can be used either by itself or in combination with other medications. 

It is important to note that Metformin does not cure diabetes, but rather is intended to help manage blood sugar levels, which can prevent complications and help reduce the burden of diabetes. 

When taking Metformin, it’s important to monitor blood sugar levels as directed by a doctor or medical professional. This may involve finger-stick glucose tests, wearing a continuous glucose monitor, and getting regular HbA1c blood tests done.

This will ensure that Metformin is continuing to work as prescribed and can help to inform if dosages need to change over time.

If you decide to stop taking metformin, the drug will stay in your system for about 4 days.

Is Metformin hard on your kidneys or heart?

Metformin is eliminated from the body through the kidneys and is flushed out through the urine. If the kidneys are not functioning properly, metformin can build up in the bloodstream, increasing the risk of lactic acidosis. 

Because of this, people with kidney impairment or kidney disease will generally be directed to avoid taking Metformin.

Further, people with pre-existing renal disease may have their kidney health further harmed by taking Metformin.

However, people who have healthy kidney function do not need to worry. There is no evidence that Metformin is hard on healthy kidneys.

Metformin is not known to have any negative effects on the heart. While it is important to talk with your doctor if you have a history of heart disease before taking Metformin, Metformin is generally considered safe for the cardiovascular system.

Research is indeterminate if Metformin is protective against heart failure, but it has been established as generally safe for people with a range of cardiac conditions.

However, as always, it is a good idea to discuss all other conditions with your doctor or care team before beginning treatment with Metformin.

Safety of Metformin for people with diabetes

Overall, Metformin is considered to be a very safe medication for people with prediabetes and type 2 diabetes. 

The benefits of Metformin in helping to control blood sugar levels and in reducing the risk of complications from diabetes outweigh the relatively small risks of serious side effects. 

Common side effects, such as gastrointestinal discomfort, are generally temporary and can be managed or eliminated by starting with small doses and gradually increasing them over time.

It is important for people with diabetes to work closely with their doctor or other medical providers to consistently monitor blood sugar levels, report and discuss side effects, and make adjustments to the treatment plan as necessary. 

Sharing any concerns you have with your medical provider helps the care team to ensure you are receiving the most appropriate care.

By asking questions about side effects and discussing other conditions and medications before beginning Metformin therapy, people with diabetes can feel confident in the safety of their treatment plan, including their prescription for daily metformin.

Frequently asked questions