Biguanides: Uses, Side Effects, Dosages, Interactions & Precautions

Medically Reviewed By: Dr. Surajeet Kumar Patra, MBBS, MD, FDIAB, MBA & APMP March 10, 2022

Biguanide class of diabetes medicines control high sugar levels in type 2 diabetics. People use them together with proper meals and exercise. Type 2 diabetes is a lifelong medical problem. In this, a person’s body fails to use insulin normally. And, thus fails to regulate the glucose circulating in the blood. Regulating high glucose levels prevents diabetes complications. These can be:

  • kidney damage
  • nerve problems
  • blindness
  • heart attack or stroke
  • sexual function problems
  • loss of limbs

Metformin is generally used as a single treatment (monotherapy). Also, it is available as a combination medicine with other diabetes drugs in a single tablet. For example:

  • metformin + sitagliptin
  • pioglitazone + metformin
  • metformin + vildagliptin

Also, Metformin is present as a blend with insulin. Type 1 diabetics take this type of combination.

How Do Biguanides Exert Their Action?

Biguanides are oral antidiabetic medications. They exert their action by:

  • preventing glucose production in the liver
  • improving the insulin sensitivity of the body, and
  • reducing glucose absorption by the intestines.

Moreover, biguanides activate the enzyme (AMPK). This enzyme increases the sensitivity to insulin. It assists cells to react more efficiently to insulin and utilize more glucose as energy. As a result, lowering the glucose concentration in the bloodstream.

Uses of Biguanides

Metformin is the only available biguanide drug. Its common use is as a first-line treatment for type 2 diabetes mellitus. Biguanides are not useful in treating insulin-dependent or type 1 diabetes. It is a health problem in which the body fails to form insulin. Biguanides are also not useful to treat diabetic ketoacidosis. In this, ketones rise in the blood or urine.

The ADA proposes certain instructions for individuals with certain high-risk factors like:

  • cardiovascular problems
  • kidney issues

These instructions are: they must begin consuming metformin with an extra therapy (with proven cardiovascular disease benefit) to assist in improving their outcomes.

Off-Label Uses

Metformin might rarely be recommended off-label for:

  • type 1 diabetes
  • overweight, and
  • polycystic ovarian syndrome.

Also, the medicine is under investigation for its potential cancer-fighting and cardioprotective benefits.

Dosage of Biguanides

People take Metformin in the doses of 500 mg to 2550 mg a day. A healthcare provider begins person’s prescription at a low dose. Slowly, doctors increase the dose as per the person’s body’s needs. Based upon the form, they take Metformin once to three times daily.

Metformin is an oral medicine for use as a tablet or liquid. Inhaled forms also come in the market. Carefully follow all the guidelines regarding the safe use of every product. Store the medicine at room temperature. Take meals with Metformin in order to prevent side effects. If a person forgets a dose, he or she must take the next dose rather than doubling that up.


Biguanides come in the forms namely, liquid and tablets: extended-release. People take this liquid in combination with meals 1-2 times a day. Take the regular tablet with meals 2 or 3 times a day. Also, take ER tablets once every day with meals. Biguanides might be recommended as a single treatment or with other diabetes medicines like pills and insulin.

Medicines in this class

As stated, Metformin is the only biguanide that comes in the market. Yet, there are 2 different versions of the medicine;

  • Metformin IR (immediate-release): People take this generally three times a day
  • Metformin SR (slow release): Take it one time a day

The brand name of Metformin IR is Glucophage. The trade name for metformin PR is Glucophage SR.


Biguanides act by preventing the liver from changing fats and amino acids to glucose. Also, these medicines activate an enzyme (AMPK). It helps cells to react to insulin and take in glucose from the blood.

Health Benefits of Biguanides

  1. Lowers down the risk of heart problems

Together with a reduction in blood glucose, biguanides help to reduce the risk of heart disease. As, it aids in reducing the levels of bad cholesterol in the blood.

  1. Biguanides are not likely to result in low blood glucose

As a single drug, biguanides are not likely to result in low blood sugars.

  1. Possible weight loss

Biguanides might assist in weight loss. Even if it is not a weight-loss drug and research does not show a huge impact on weight loss.


Metformin lowers the liver’s blood sugar raising effect. The medicine also helps to reduce sugar levels all over the day. Metformin also increases the body’s sensitivity to insulin. And, thus, it has benefits for weight loss.

Possible Side Effects of Biguanides

  1. Lack of vitamins

Chronic usage of this medicine relates to vitamin B12 deficiency in the body.

  1. Gastrointestinal intolerance

Common ill effects, particularly while starting its use, can be:

  • vomiting
  • nausea
  • bloating
  • loose stools
  • abdominal uneasiness.
  1. Lactic acid accumulation

This category of drugs gets eliminated from the body via kidneys. Also, in the absence of kidney function, high amounts start moving in the body. When the level of biguanides become high in the body, it might cause lactic acidosis. Also, the incidence of this complication is very rare. Discuss with a healthcare provider about this risk. If healthcare provider has recommended a biguanide, speak to them. A health care provider may answer all these questions and work with them. This helps in managing any side effects.


As a single medicine, metformin consumers are not likely to experience hypoglycemia or weight gain. Yet, the risk of such side effects enhances if Metformin is taken with insulin or a sulphonylurea.

Interactions with Biguanides

When 2 or more medicines are taken in combination, their work might get changed. And, the risk of ill effects also increases. This is termed as Drug Interaction.

Other medications

Medications that interact with biguanides may include:

  • corticosteroids
  • oral contraceptives
  • estrogens
  • phenothiazines
  • thyroid medications
  • anticonvulsants such as phenytoin
  • drugs for rectifying vitamin B deficiency.

While interacting with these medicines, biguanides fail to control blood sugar levels. Proper monitoring of glucose levels is necessary in such patients.

Safety Precautions While Taking Biguanides

Serious Conditions of Vomiting, Diarrhea, or Fever

Individuals with severe conditions of vomiting, diarrhea, or fever may suffer from dehydration. They may suffer from a severe water loss in the body. Stop the use of biguanides for a shorter time duration. Also, consult with a doctor about this.

Alcohol Consumption

Too much alcohol may result in the accumulation of lactic acid in the body. The condition is lactic acidosis. Hence, individuals should not have alcohol while taking biguanides.

Iodinated Contrast Agents

The use of iv iodinated contrast agents may enhance the building up of lactate in the body. This lessens the working of the kidneys. Stop using biguanides prior to or at the time of treatment with these agents for 48 hours. Recommence the usage of biguanides if kidney functioning becomes stable.

Elderly Patients

Proper kidney monitoring is important in elderly patients. Avoid giving biguanides to elderly patients.


Patients under anaesthesia at the time of surgical procedures are at high risk on biguanides. They must stop its use while going through surgery for at least 48 hours. Recommence its use after the restitution of oral nutrition. Also, when the kidney working becomes stable, a person can take it.

Heart Failure

Patients experiencing heart failure are at high risk while on biguanides. These patients are at an increased risk of low oxygen levels in the blood. And, also an irregular kidney working. A low oxygen level in the blood is hypoxemia. In people having chronic heart failure, good monitoring of the heart and kidney is vital. The use of biguanides is not safe in people with unstable heart failure.


What are the benefits of biguanides?

Biguanides are anti-diabetes medicines useful for type 2 diabetics. This medicine prevents glucose production in the liver. It improves the body’s sensitivity towards insulin. Also, biguanides lowers down the amount of sugar absorbed by the intestines.

Which of the following disinfectant falls under the category of biguanides?

The disinfectants chlorhexidine, polihexanide, polyaminopropyl biguanide (PAPB), and alexidine belong to biguanide groups.

Is biguanides a disinfectant?

Polyhexamethylene biguanide (PHMB) is an extensively used biocide for several applications. It is useful as a disinfectant in:

  1. swimming pools
  2. food industry
  3. hospitals as an antiseptic agent for curing wound infections

Can biguanides result in hypoglycemia?

Biguanides do not enhance plasma insulin concentrations. Also, these medicines do not cause serious hypoglycemia. As a result, they are known as antihyperglycemic (instead of hypoglycemic) drugs.



 Last Updated on by Dr. Damanjit Duggal 


The information included at this site is for educational purposes only and is not intended to be a substitute for medical treatment by a healthcare professional. Because of unique individual needs, the reader should consult their physician to determine the appropriateness of the information for the reader’s situation.

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