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Metformin does not cause high blood pressure. Most studies show it has a neutral effect on blood pressure, and some research even reports small reductions. For example, a meta-analysis found metformin lowered systolic blood pressure by about 2 mmHg on average.

However, some people taking metformin still notice higher blood pressure readings and wonder whether the medication is responsible.

To understand why this can happen, let’s look at how blood pressure works, how metformin affects metabolism and blood vessels, and what other factors may influence blood pressure while taking the drug.

Key Takeaways

  • Metformin does not cause high blood pressure. Research shows it may slightly lower blood pressure, with an average 2 mmHg reduction in systolic pressure, and larger drops in people with impaired glucose tolerance (5 mmHg) or obesity (3 mmHg).
  • Metformin may support blood vessel health. It activates protective pathways such as AMPK, increases nitric oxide, and may improve kidney and gut functions that influence blood pressure.
  • Talk to your doctor if your blood pressure changes. A healthcare provider can check for other causes and adjust treatment if needed.
  • Save on diabetes and blood pressure medications. With a prescription, you can get metformin starting at $13.99 per 100 tabs and lisinopril for $69 per 100 tabs, plus an additional 10% discount may apply.

Understanding blood pressure and hypertension

Blood pressure (BP) is a measure of the force that circulating blood exerts on the walls of arteries. It is recorded as two numbers:

    • Systolic pressure (the top number) reflects pressure when the heart pumps, and
    • Diastolic pressure (the bottom number) reflects pressure when the heart relaxes between beats.

You may see a reading such as 120/80 mmHg (“millimeters of mercury”).

Persistent high blood pressure strains blood vessels and forces the heart to work harder. Over time, uncontrolled hypertension damages the arteries and increases the risk of heart attack, stroke, kidney disease, and other complications. According to the American Heart Association (AHA), controlling high blood pressure can significantly reduce your risk of these major health problems.

The AHA categorizes blood pressure levels as follows:

Category

 Systolic (mmHg)

Diastolic (mmHg)
Normal

Less than 120

 and

Less than 80
Elevated

120-129

 and

Less than 80
Stage 1 hypertension

130-139

 or

80-89
Stage 2 hypertension

140 or higher

 or

90 or higher
Hypertensive crisis (emergency)

Over 180

 and/or

Over 120

If your reading consistently falls in the elevated or hypertensive range, your healthcare provider may recommend lifestyle changes or medication to prevent cardiovascular disease.

What is metformin and who is it for?

Metformin is a first-line medication for type 2 diabetes. It helps lower blood sugar through the following processes:

    • reducing sugar production in the liver
    • improving the body’s response to insulin

Recent studies also suggest that metformin works partly in the gut. It can lower how much sugar the intestines absorb, change the gut microbiome, and increase the release of GLP-1 and certain bile acids. These effects may help improve blood sugar control and provide other health benefits.

Because many people newly diagnosed with type 2 diabetes are overweight, metformin’s neutral or modest weight-reducing effect makes it a preferred initial therapy.

About 20% of people taking metformin experience gastrointestinal symptoms such as:

    • nausea
    • vomiting
    • diarrhea
    • bloating

Metformin can also reduce vitamin B12 absorption, so long-term users may develop a deficiency. Serious side effects such as lactic acidosis are rare.

Does metformin cause high blood pressure?

Metformin does not cause high blood pressure. Studies suggest it may even help lower blood pressure and cardiovascular health, particularly in people with type 2 diabetes or PCOS, partly by improving insulin resistance.

A meta-analysis of 4,113 people found that metformin lowered systolic blood pressure by about 2 mmHg on average, with larger reductions in those with impaired glucose tolerance (5 mmHg) and obesity (3 mmHg).

A genetic study of 175,648 people also found that metformin-related pathways were linked to a 13% lower risk of hypertension. The analysis also showed small reductions in blood pressure, including about 1.05 mmHg lower systolic pressure and 0.51 mmHg lower diastolic pressure.

How does metformin lower blood pressure?

Metformin may help lower blood pressure through several biological effects in the body.

1. Activation of AMPK

Metformin activates AMP-activated protein kinase (AMPK), an enzyme that regulates cellular energy balance. AMPK activation improves insulin sensitivity and reduces glucose production in the liver. It also supports blood vessel health by increasing nitric oxide, a molecule that helps blood vessels relax and widen, while reducing inflammation and oxidative stress.

AMPK activation can also increase protective proteins that help cells defend against oxidative damage. By lowering oxidative stress, metformin may indirectly help reduce blood pressure.

Metformin also stimulates autophagy, a process that allows cells to recycle damaged components. At the same time, it improves mitochondrial function, helping cells produce energy more efficiently. These effects may protect blood vessels from damage associated with hypertension.

2. Healthier blood vessels

Metformin may improve the health of the inner lining of blood vessels, called the endothelium. It may also reduce cellular stress and inflammation in blood vessels. Researchers tested this by giving mice a hormone called angiotensin II, which raises blood pressure and causes damage to blood vessels.

After two weeks, the mice developed high blood pressure and stress inside their blood vessel cells. However, mice that also received metformin showed less cellular stress and healthier blood vessels.

3. Changes in gut bacteria

Metformin may also influence blood pressure through its effects on the gut microbiome. The drug increases beneficial gut bacteria that produce short-chain fatty acids (SCFAs). These compounds can interact with receptors in the body that help regulate blood pressure.

In studies involving hypertensive rats, metformin increased SCFA production, lowered blood pressure, and reduced inflammation.

4. Helping the kidneys remove excess sodium

Metformin may also help the kidneys remove excess salt from the body, which is important in people with salt-sensitive hypertension. Researchers studied diabetic mice that were fed extra salt, which caused high blood pressure and worsening kidney damage. The mice that received metformin had lower systolic blood pressure compared with those that did not receive the drug.

The researchers found that metformin reduced a protein in the kidneys called cathepsin B. Lower levels of this protein reduced the activity of a sodium channel (ENaC) that normally causes the body to retain salt.

Because less salt was reabsorbed by the kidneys, more sodium was removed in the urine. This helped lower blood pressure.

5. Blocking hormones that raise blood pressure

Angiotensin II is a hormone that makes blood vessels tighten, which raises blood pressure. Metformin may help counter this effect by activating protective cellular pathways and reducing inflammation and oxidative stress.

These benefits may be especially helpful for people with diabetes or metabolic syndrome, where blood pressure-raising systems in the body are often more active.

Why might blood pressure increase while taking metformin?

Why might blood pressure increase while taking metformin?

Metformin itself does not usually raise blood pressure, and many studies suggest it may slightly lower it. However, if you notice higher blood pressure while taking the medication, it might be related to other health factors.

Worsening blood sugar control

When blood glucose stays high for long periods, it can damage the inner lining of blood vessels, making them less flexible. High blood sugar can also increase inflammation and cause your body to retain more sodium and fluid, both of which may raise blood pressure.

If you notice your blood pressure increasing while taking metformin, it may be a sign that your blood sugar is not as well controlled as before. In that case, it’s best to consult your doctor. They may review your blood glucose levels and recommend adjustments, such as changes in diet or physical activity, modifying your metformin dose, or adding another diabetes medication to improve blood sugar control.

Weight changes or fluid balance

While many people lose weight on metformin, shifts in diet, hydration, or salt intake can influence how much fluid your body retains. Holding on to more sodium and water can increase blood volume, which may raise blood pressure.

If you notice changes in your weight, swelling, or rising blood pressure, it may help to review your diet, hydration, and sodium intake. If the increase continues, a healthcare provider can help determine whether adjustments to your diet, medications, or treatment plan are needed.

Other medications

Sometimes blood pressure rises because of other medications taken alongside metformin. Certain drugs are known to increase blood pressure. These include:

    • Steroids
    • Decongestants
    • NSAIDs
    • Hormonal medications

If you started a new medication around the same time your blood pressure increased, it may be worth discussing this with your doctor. They can review your medications and determine whether a drug interaction or side effect may be contributing to the change.

Kidney or hormonal conditions

Your kidneys and hormones help regulate fluid balance and blood pressure. If a kidney condition or hormonal imbalance develops, blood pressure may rise regardless of the medications you take.

If your blood pressure becomes harder to control, your doctor may check kidney function, hormone levels, or other related conditions. Identifying and treating these issues can help bring blood pressure back to a healthier range.

Stress, diet, and lifestyle factors

Daily habits can also influence your blood pressure. High sodium intake, lack of physical activity, poor sleep, and ongoing stress can all cause blood pressure to increase.

If your readings start to rise, it may help to review your diet, exercise habits, sleep, and stress levels. Small lifestyle adjustments can often make a meaningful difference, and your healthcare provider can help guide you toward strategies that support both blood sugar and blood pressure control.

What should you do if your blood pressure increases on metformin?

If you notice higher blood pressure while taking metformin, it is important not to stop the medication without medical advice.

Consider these steps:

    • Monitor your blood pressure regularly to see if the change is consistent.
    • Review other medications or supplements with your doctor.
    • Check your diet, especially sodium intake.
    • Discuss symptoms with a healthcare provider, who may evaluate kidney function, blood sugar control, or other causes.

In many cases, adjusting lifestyle factors or treating underlying conditions can help bring blood pressure back to normal.

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Bottom line

Worries that metformin might cause high blood pressure are not supported by scientific evidence. On the contrary, most clinical studies show a modest reduction in blood pressure, particularly in people with insulin resistance or obesity. Genetic and animal studies also suggest that metformin may help protect blood vessels. These benefits may come from activating AMPK, increasing nitric oxide, and improving gut and kidney function.

Medication decisions should always be discussed with your healthcare provider, who can consider your overall health and treatment goals.

Frequently Asked Questions

Metformin is not known to cause sudden increases in blood pressure. Most studies show it has a neutral effect or may slightly lower blood pressure. If spikes occur, they are usually related to other health factors or medications.

The most common side effects are nausea and diarrhea. Some people also experience stomach discomfort or bloating, especially when starting the medication. These symptoms often improve as the body adjusts.

Most diabetes medications do not raise blood pressure, and some may even help improve cardiovascular health. However, blood pressure can still increase due to diabetes progression, kidney disease, or other medications. A healthcare provider can help identify the cause.

For most adults with diabetes, doctors recommend keeping blood pressure below 130/80 mmHg. Maintaining blood pressure in this range helps reduce the risk of heart disease, stroke, and kidney damage. Targets may vary depending on individual health conditions.

Yes, people with diabetes frequently develop high blood pressure. Both conditions share risk factors such as insulin resistance, obesity, and blood vessel damage. When they occur together, the risk of cardiovascular complications increases.

High blood pressure often has no noticeable symptoms, which is why it is sometimes called a “silent” condition. Many people only discover it during routine blood pressure checks. Severe hypertension may occasionally cause headaches or dizziness.

Yes, diabetes and high blood pressure are closely linked. High blood sugar can damage blood vessels and make them less flexible, which can raise blood pressure. Having both conditions increases the risk of heart and kidney disease.

A reading of 140/90 mmHg is considered high blood pressure. It does not usually require emergency care, but it should be discussed with a healthcare provider. Lifestyle changes or medication may be recommended to lower it.

Common causes include genetics, lifestyle factors, and underlying health conditions. A diet high in sodium, lack of exercise, and obesity can increase risk. Kidney disease and hormonal disorders can also contribute.

If blood pressure rises suddenly, sitting quietly and practicing slow breathing may help bring it down slightly. Avoid caffeine, nicotine, and stressful activity during that time. Long-term control usually requires lifestyle changes or prescribed medication.

Check your blood pressure if possible, and rest in a calm environment. Avoid stimulants like caffeine or nicotine and monitor how you feel. If symptoms such as chest pain, severe headache, or shortness of breath occur, seek medical attention.

Untreated hypertension can damage blood vessels and vital organs over time. It increases the risk of heart disease, stroke, kidney disease, and vision problems. Regular monitoring and treatment help reduce these risks.

A reading of 160/100 mmHg is considered stage 2 hypertension and should be evaluated by a healthcare provider. It is not usually an emergency unless symptoms such as chest pain, severe headache, or neurological problems occur. In those cases, immediate medical care is recommended.

Common warning signs include sudden weakness on one side of the body, difficulty speaking, facial drooping, sudden vision problems, and severe headache. These symptoms often appear suddenly. Immediate emergency care is critical if they occur.

Blood pressure readings of 180/120 mmHg or higher are considered a hypertensive crisis in older adults. This level can lead to serious complications such as a stroke or heart attack. Immediate medical evaluation is necessary.

Related Articles

Sources

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