Unraveling the Mystery: How Long Does it Take for Metformin to Work?
Metformin is a medication used for decades to treat type 2 diabetes. Due to its low-cost and safety profile, it is the first choice for treating diabetes (along with diet and exercise), and the American Diabetes Association (ADA) also recommends using metformin for treating prediabetes.1
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How does metformin work?
In people with type 2 diabetes, insulin is either not produced in high enough quantities, or body tissues are resistant to its effects. This is called insulin resistance. The pancreas continues to pump out more and more insulin, but the body tissues cannot use it effectively. This results in high insulin and high blood sugar levels.
Metformin has the following effects:2
- Lowering glucose production in the liver
- Decreasing glucose absorption from the intestines
- Increasing insulin sensitivity
Metformin does not directly decrease blood sugar like insulin, so it is not used to treat type 1 diabetes. However, it does lower blood sugar, which can have implications for your health. High blood sugar levels damage blood vessels, increasing your risk for cardiovascular disease, kidney disease, and accelerated cognitive decline.
Type 2 diabetes, obesity, and metabolic syndrome are closely related chronic diseases that involve the endocrine system and metabolism. Improving your blood sugar and managing your weight can improve many aspects of your health.
Because of its effects on blood sugar and weight, and its ability to reduce cardiovascular risks and moderate cell growth, metformin has been investigated as an anti-aging, thyroid, and cancer treatment. It is also used off-label to treat polycystic ovary syndrome.3
Proposed mechanisms of action for metformin’s weight loss and metabolic effects include:4
- Decreasing liver glucose production
- Altering gut microbiome
- Suppressing appetite-stimulating brain cells in the hypothalamus
- Increasing leptin sensitivity
- Suppressing appetite by increasing lactate production
- Reversing age-related metabolic changes
- Altering bile absorption
- Changing signaling in the gut
Does metformin lower blood sugar immediately?
Metformin does not work like insulin and therefore does not immediately affect your blood sugar.
How long does it take for metformin to work for weight loss?
Metformin starts to work within the first few days after starting treatment, but it may take two to three months to get your blood sugars under control.
Metformin is typically prescribed to control your blood sugar. Weight loss is a beneficial side effect. In one study, people who took metformin for up to six months lost an average of 10 to 14 pounds, which was 5.6% to 6.5% of their body weight.5 In another study, participants lost between 4.5% and 6.5% of their body weight after taking metformin as part of a weight loss program.6 A weight loss of 5% of your body weight has been shown to have important health benefits.
What are the signs that metformin is working?
The best way to determine whether metformin is working is to check your blood sugars using blood sugar testing supplies or a continuous glucose monitor. Your doctor may also order a HbA1c. This test measures glycated hemoglobin, an average of your blood sugar over two to three months.
If you are taking metformin for weight loss, check your weight daily, then average your daily weights and record a weekly average. Daily weights fluctuate in response to what you eat, stress, and how much fluid and stool you have in your intestines. A weekly average is more accurate.
What is the best time to take metformin?
Metformin is generally taken with meals, either once or twice a day, to mitigate its gastrointestinal side effects. Diarrhea is the most common side effect; slowly increasing the dose can often reduce or prevent metformin-associated diarrhea.
What are potential metformin side effects?
Metformin does not have significant adverse effects, except it can rarely cause lactic acidosis. Symptoms of lactic acidosis include:3,7,8
- Severe drowsiness
- Muscle pain
- Bluish tinge to skin color
- Fast breathing
- Changes in heartbeat
- Stomach pain
Serious allergic reactions may occur, but they are unusual. Other potential side effects include:
- Gastrointestinal symptoms
- A metallic taste
Metformin can cause vitamin B12 deficiency. Watch for symptoms associated with vitamin B12 deficiency, such as:
- Muscle weakness
- Sore, red tongue
- Mouth ulcers
- Visual symptoms
- Pale or yellowing tinge to skin color
What foods should I avoid when taking metformin?
Glycemic index and glycemic load are two measures that indicate how foods affect blood sugar levels. The glycemic index ranks foods from 0 to 100, with foods assigned a score of 100 having the biggest impact on blood sugar. Pure sugar, for example, is scored as 100. Avoid foods with a high glycemic index. These foods can cause rapid increases in blood sugar. Foods that have a lower glycemic index cause less abrupt increases.
Glycemic load is calculated as the glycemic index multiplied by the amount of carbohydrates in a serving, divided by 100. Foods with a higher glycemic load cause higher peaks in blood sugar than those with a lower glycemic load. Consult International Tables of Glycemic Index and Glycemic Load Values: 2008 for a helpful database of foods with their glycemic index and glycemic load.
Metformin synergy combines medications that aid in weight loss and blood sugar control. It can also bring down triglyceride levels, thus lowering the probability of cardiovascular disease. Managing your weight can ultimately decrease your risk of three chronic diseases associated with premature aging: obesity, type 2 diabetes, and cardiovascular disease. Have questions about metformin and how it can improve your health? Contact one of the Invigor Medical treatment specialists today to get all your questions answered.
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- American Diabetes Association. 9. Pharmacologic Approaches to Glycemic Treatment: Standards of Medical Care in Diabetes—2022. Diabetes Care. 2022;45(Supplement 1): S125–S143. doi:10.2337/dc22-S009
- Nasri H, Rafieian-Kopaei M. Metformin: Current knowledge. J Res Med Sci. 2014 Jul;19(7):658-64. PMID: 25364368; PMCID: PMC4214027.
- Yerevanian A, Soukas AA. Metformin: Mechanisms in Human Obesity and Weight Loss. Curr Obes Rep. Jun 2019;8(2):156-164. doi:10.1007/s13679-019-00335-3
- Yanovski JA, Krakoff J, Salaita CG, McDuffie JR, Kozlosky M, Sebring NG, Reynolds JC, Brady SM, Calis KA. Effects of metformin on body weight and body composition in obese insulin-resistant children: a randomized clinical trial. Diabetes. 2011 Feb;60(2):477-85. doi: 10.2337/db10-1185. Epub 2011 Jan 12. PMID: 21228310; PMCID: PMC3028347.
- Scheen AJ, Paquot N. Metformin revisited: A critical review of the benefit-risk balance in at-risk patients with type 2 diabetes. Diabetes Metab. 2013;39:179–90.
- Nasri H, Behradmanesh S, Maghsoudi AR, Ahmadi A, Nasri P, Rafieian-Kopaei M. Efficacy of supplementary vitamin D on improvement of glycemic parameters in patients with type 2 diabetes mellitus: A randomized double blind clinical trial. J Ren Inj Prev. 2014;3:31–4.