Metformin is generally safe, but has many rare and serious side effects.
In this article, we investigate the relationship between metformin and one serious potential side effect known as lactic acidosis.
What is lactic acidosis?
Lactic acidosis is a serious condition in which lactic acid accumulates in the bloodstream, making blood chemistry a dangerous acidity.
Lactic acidosis has many underlying causes, but it is generally the result of either a fundamental condition, addiction, or side effects from a drug.
Symptoms of lactic acidosis vary from person to person, but can include:
- Abdominal pain or discomfort
- Nausea and vomiting
- Reduced appetite
- Persistent diarrhea
- Muscle pain and convulsions
- Increased heart rate
- Dyspnea, rapid breathing, or hyperventilation
- Common pains that may be difficult to explain
- Lethargy, fatigue, or weakness
- Changes in mental states, including sleepiness, confusion, and loss of consciousness
Lactic acidosis can be a life-threatening emergency without treatment.
If you are experiencing these symptoms or believe you have lactic acid disease, seek emergency medical care immediately.
Can methorn cause lactic acid disease?
The US Food and Drug Administration (FDA) metformin approval includes warnings regarding the possible drug therapy that causes lactic acidosis.
However, the rate of lactic acidosis in people taking metformin is so low that it is difficult for researchers to see if the drug is liable or if it is caused by other underlying factors.
A large study reported in 2022 examined 4,241 suspected cases of metformin-related lactic acidosis and found that only sufficient data (9%) to support such a diagnosis highlighted the rarity of this condition.
The estimated incidence of metformin-related lactic acidosis is approximately 6.3 cases per 100,000 people per year.
Statistically, this means that if 100,000 people take metformin for a year, they expect less than about six instances of people experiencing this rare side effect.
Although it is a small number compared to the side effects of other drugs, lactic acidosis is a serious condition. It is important for people taking metformin to recognize it.
Are there any risk factors for lactic acid disease?
There are many risk factors for experiencing lactic acidosis while taking metformin.
These risk factors are:
- There is a kidney problem (renal (kidney) disorder or kidney disease) and the risk increases with the severity of the disease
- dehydration
- You are also taking medications such as topiramate (brand name: Topax, Topiragen) and other carbonate antilase inhibitors, which increases the risk of lactic acid disease
- Over 65 years old
- Have received medical imaging procedures that need to be administered with a specific IV extended contrast agent
- Experience acute congestive heart failure
- Liver problems and chronic or heavy alcohol use
Recent surgeries and various other health conditions, particularly those affecting the liver, heart, or kidneys, can also increase the risk of lactic acid disease.
Check your full health history with your doctor and ask about the steps required before starting a new metformin prescription.
What are the symptoms of lactic acidosis when taking metformin?
The core symptoms of lactic acidosis tend to be similar, whether or not they are side effects against metformin.
These symptoms include:
- Abdominal pain and stomach upset
- Muscle pain and convulsions
- Nausea and vomiting
- Reduced appetite
- Difficulty breathing or quick, shallow breathing
- Increased heart rate
- Lethargy, fatigue, or weakness
- Changes in mental state
- General pain
According to the FDA, the onset of metformin-related lactic acidosis is something like “often subtle, nonspecific symptoms only” (a common sense of discomfort), difficulty breathing, and drowsiness.
This tends to appear suddenly, unlike other causes, as it is lactic acidosis.
It is important to note that metformin-related lactic acidosis is a rare occurrence.
However, if left untreated, the condition can be debilitating or fatal, so suspected lactic acidosis should be treated as a medical emergency and immediately seeking care.
How long does it take for metformin to develop lactic acid disease?
Lactic acidosis can occur quickly in case of metformin overdose.
A clinical case report published in 2020 described people who had a significant overdose of metformin and developed lactic acid disease by the time they arrived in the emergency department four hours later.
Acute overdose can cause lactic acidosis quickly, but it is important to continue to recognize symptoms of the condition long after you start taking metformin.
Metformin-related lactic acidosis is very rare, so there is no established time frame for how long it usually takes to develop a condition.
Therefore, it is important to keep your doctor informed of health conditions and changes that could increase the risk of lactic acid.
How is diabetic ketoacidosis different from lactic acidosis?
Diabetic ketoacidosis (also known as DKA) and lactic acidosis are two different conditions, both of which involve imbalance in the acidity level of the blood.
Each can be life-threatening, but they are attributed to different underlying causes.
DKA is a serious diabetic complication that can occur when blood glucose levels are too high (a condition known as hyperglycemia) is too long.
DKA is characterized by the presence of ketones (chemical by-products of the breakdown of fats to energy) in the blood and urine.
The accumulation of ketones in the blood leads to an increase in acidic substances called ketone bodies, making the blood more acidic and can cause short- and long-term damage.
Lactic acidosis, on the other hand, is a condition in which the accumulation of lactic acid in the bloodstream makes the blood more acidic.
It can be caused either by increased lactic acid production or by impaired body’s ability to clean lactic acid.
Like DKA, lactic acidosis can lead to significant short- and long-term damage and should be considered an emergency.
Both conditions are dangerous and require immediate medical consultation.
