Supplement: metformin kills cancer stem cells

Metformin plant Galega Officinalis

Galega officinalis – source of Metformin
photo credit: wikipedia

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Updated 19 Jan 2014 with additional links to metformin and chemotherapy and radiotherapy, and dosage recommendations

Metformin is a drug that is usually used to control sugar level in people with Type 2 diabetes.

Tests have also shown that it may also be effective in reducing cancer risk, improving the survival of people with cancer, and inducing cancer cell death.

Metformin has been shown to selectively target and kill some lines of breast cancer stem cells.  As stem cells are usually resistant to chemotherapy, metformin is another tool you want to have in your kit.

It is speculated that metformin works by blocking a metabolic stress response that stimulates the inflammatory pathway associated with a wide variety of cancers. The source of metformin is the herb Galega officinalis (French lilac, also known as Goat’s Rue or Italian Fitch) and has been used as a traditional botanical.

Please note, even though it controls sugar levels, metformin is not an excuse for pigging out on carbohydrates or sugar-rich foods!


I was started out at 250mg once a day at Hallwang, with a meal containing carbohydrates.  Metformin should always be taken with meals.

I’ve looked for recommendations, and found this on Life Extension Magazine – Metformin:  Dosing:

“For people who want to derive the many proven health benefits of metformin, it might be prudent to follow the dosage schedule used by Type II diabetics. According to the Physician’s Desk Reference, the starting dose should be 500 mg of metformin twice a day. (An alternative option is 850 mg of metformin once a day).

After one week, increase the dose of metformin to 1000 mg as the first dose of the day and 500 mg as the second dose. After another week, increase to 1000 mg of metformin two times a day. The maximum safe dose described in the Physician’s Desk Reference is 2550 mg a day (which should be taken as 850 mg three times a day).

According to the Physician’s Desk Reference, clinically significant responses in Type II diabetics are not seen at doses below 1500 mg a day of metformin. Anti-aging doctors, on the other hand, have recommended doses as low as 500 mg twice a day to healthy non-diabetics who are seeking to obtain metformin’s other proven benefits such as enhancing insulin sensitivity and reducing excess levels of insulin, glucose, cholesterol and triglycerides in the blood.

It could be the dosage range is highly individualistic in healthy people, meaning some may benefit from 500 mg twice a day, while others may need 1000 mg twice a day for optimal effects.”

[the article further recommends blood tests to ensure that the level of glucose, insulin and red blood cells is improved by taking metformin]

Here are more guidelines from the Mayo Clinic:

Drug interactions

If you are on Cimetidine (Tagamet) for cancer, Cimetidine decreases the elimination of metformin from the body, and can increase the amount of metformin in the blood by 40%. This may increase the frequency of side effects from metformin.

Where can you get it from?

Therein lies the dilemma.  The use of metformin as a treatment for cancer is currently off-label.  In the UK, if you’re not a diabetic, you won’t be able to get it on prescription from your GP, but your GP might be one of the more enlightened ones, so try.  Alternatively, speak to your oncologist, print off the articles below and get your oncologist to write the prescription.

Articles on metformin

Here is an excellent article from Life Extension Magazine explaining the mechanism of metformin:

Can a Diabetes Drug Prevent Cancer Death?

Metformin inhibits the inflammatory response associated with cellular transformation and cancer stem cell growth (research conducted by Kevin Struhl, Struhl Lab, Harvard University)

Metformin Decreases the Dose of Chemotherapy for Prolonging Tumor Remission in Mouse Xenografts Involving Multiple Cancer Cell Types (research conducted by Kevin Struhl),%202011%20Cancer%20Res%20metformin.pdf

Metformin kills and radiosensitizes cancer cells and preferentially kills cancer stem cells

Metformin is synthetically lethal with glucose withdrawal in cancer cells

Diabetes, Metformin, and Breast Cancer in Postmenopausal Women

7 August 2013 – just read an article about how the herb Berberine can have as many effects as metformin in controlling diabetes – so here’s a way of controlling glucose levels.  It also has anti-cancer properties.


Please note, metformin is not a substitute for a low-carb/sugar diet !!!

Poor glucose control could reduce metformin’s anti-cancer benefits

A diet high in processed carbs and sugar can cause a recurrence in colon-cancer survivors, all the more reason to add metformin to your daily supplements:

“Dietary energy availability affects primary and metastatic breast cancer and metformin efficacy” – it make a strong case for calorie restriction.