Metformin is a popular prescription drug that is used as a first-line treatment for prediabetes and type 2 diabetes. It is usually taken orally, in pill form, once or twice a day.
Metformin helps people control blood sugar levels. It reduces insulin resistance and has been shown to help people lose weight.
In this article, we will explore the safety profile of metformin and its links to diabetes.
How does metformin work?
Metformin is one of the most commonly prescribed prescription drugs in the United States, with millions of prescriptions issued to people each year.
Metformin, taken once or twice a day by mouth, belongs to a class of drugs called biguanides. These drugs are used to combat high blood sugar and are most commonly used in people with prediabetes, gestational diabetes, and type 2 diabetes.
Metformin works through multiple channels simultaneously.
The drug lowers the amount of sugar produced by the liver, reduces the absorption of sugar in the intestines, and allows individual cells in the body to consume more sugar and use it more efficiently.
Together, these three physiological changes reduce 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, a common measure of blood sugar levels, drop by about a percentage point over time, which translates to significantly lower blood sugar levels.
Who shouldn’t take metformin?
It’s important to know that not everyone should take metformin.
People with kidney problems should use metformin with caution, and people with kidney problems over the age of 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 lactating women or children, although there is reason to expect it to be effective. Nevertheless, use in these populations is generally approached with caution.
Metformin is also not recommended for people with 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 significantly improve other health outcomes.
Finally, some people may have an allergic reaction to metformin and therefore should not take the drug. Similarly, people who have experienced a condition called metabolic acidosis while taking the drug are generally advised not to take metformin again.
Because metformin can also interact with many other prescription medications, it’s important to discuss any other prescriptions with your doctor or healthcare provider before getting a prescription.
What are the dangers of taking metformin?
It’s important to know that Metformin is generally considered a safe drug, 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 the rapid buildup of lactic acid in the blood.
Clinical trials have shown metformin lactic acidosis to be rare, occurring in only about 6 people a year out of every 100,000 people taking the drug, but the condition can be fatal if not treated quickly.
Symptoms of lactic acidosis include abdominal pain, muscle spasms, difficulty breathing, and fatigue.
Another potential risk of taking metformin is that it can cause a decrease in vitamin B12 levels.
Long-term B-12 deficiency, which can also occur with anemia, can cause neurological problems, weakness, and fatigue.
A study of 1,111 patients with type 2 diabetes found that the risk was greatest in those who had been taking metformin for more than 6 months and who were taking more than 1,500 mg of the drug a day.
Vitamin B-12 supplementation and a healthy diet protect against this potential side effect.
There are also other less dangerous side effects of metformin.
The most common side effects include:
- Bloating or excessive gas
- Stomach cramps
- Upset stomach
- Nausea and vomiting
- Diarrhea
- Hypoglycemia (low blood sugar)
Most GI side effects will subside over time and can be alleviated or avoided altogether if a person starts with a low dose and increases it over time
If side effects persist or you experience any serious side effects, it is important to discuss them with your doctor or other healthcare provider.
You can read ours comprehensive guide to metformin side effects for more information.
How long can you be on metformin?
There is no fixed amount of time a person can take metformin. Metformin is considered a long-term treatment for pre-diabetes and type 2 diabetes.
However, the effectiveness of metformin in regulating blood sugar levels may decrease slightly over time. For this reason, your health care team may recommend that people who have been taking the drug for many years increase their dose from time to time.
Metformin therapy is tailored to each individual, and the long-term treatment plan depends on the person’s response and treatment goals, as well as whether or not they are experiencing any side effects of the medicine.
Metformin is also useful because it can be used alone or in combination with other drugs.
It is important to note that metformin does not cure diabetes, but is intended to help control blood sugar levels, which may prevent complications and reduce the burden of diabetes.
It is important to monitor your blood sugar levels as directed by your doctor or healthcare professional while taking metformin. This may include fingerstick glucose testing, wearing a continuous blood glucose meter, and having regular HbA1c blood tests.
This will ensure that metformin continues to work as directed and can help inform you if the dosage needs to be changed over time.
Read more: Signs Metformin Is Working (or Not Working).
Does metformin tax the kidneys or the heart?
Metformin is excreted from the body by the kidneys and flushed out in the urine. If your kidneys are not working properly, metformin can build up in your bloodstream, increasing your risk of lactic acidosis.
For this reason, people with impaired kidney function or kidney disease will generally be directed to avoid taking metformin.
What’s more, taking metformin may further worsen the kidney health of people with pre-existing kidney disease.
However, people who have healthy kidneys need not worry. There is no evidence that metformin harms healthy kidneys.
It is not known whether metformin has any negative effects on the heart. While it’s important to talk to your doctor if you have a history of heart disease before taking metformin, metformin is generally considered safe for the cardiovascular system.
Research is inconclusive as to whether metformin protects against heart failure, but it has been established that it is generally safe for people with a variety of heart conditions.
However, as always, it is a good idea to discuss any other medical conditions with your doctor or care team before starting treatment with metformin.
Safety of metformin for people with diabetes
Overall, metformin is considered a very safe drug for people with prediabetes and type 2 diabetes.
The benefits of metformin in controlling blood sugar levels and reducing the risk of diabetes complications outweigh the relatively small risk of serious side effects.
Common side effects, such as gastrointestinal discomfort, are generally temporary and can be managed or eliminated by starting with low doses and gradually increasing over time.
It’s important for people with diabetes to work closely with their doctor or other healthcare professionals to continuously monitor their blood sugar levels, report and discuss side effects, and adjust their treatment plan as needed.
Sharing any concerns with your doctor helps the care team ensure you are getting the most appropriate care.
By asking questions about side effects and discussing other conditions and medications before starting metformin therapy, people with diabetes can feel confident about the safety of their treatment plan, including their daily metformin prescription.
Frequently asked questions
Yes. The maximum recommended dose of immediate-release metformin oral tablets is 2550 mg per day.
If you are taking more than 2,000 mg of metformin per day, you may benefit from dividing it into 2-3 smaller doses throughout the day to minimize the risk of gastrointestinal side effects.
The recommended HbA1c value for metformin varies based on many factors. In general, however, metformin may be recommended when someone’s fasting glucose is above 100 mg/dL and their 2-hour postprandial blood sugar is 140-199 mg/dL.
If HbA1C is consistently above 5.7%, metformin may also be recommended.
Some brands of metformin include Fortamet, Glucophage, Glucophage XR, Glumetza, Riomet, and Riomet ER.
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