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The following information comes from DailyMed, an FDA label information provider.

Adverse Reactions

In a US double-blind clinical study of metformin hydrochloride tablets in patients with type 2 diabetes, a total of 141 patients received metformin hydrochloride tablets therapy (up to 2550 mg per day) and 145 patients received placebo. Adverse reactions reported in greater than 5% of the metformin hydrochloride tablets patients, and that were more common in metformin hydrochloride tablets – than placebo-treated patients, are listed in Table 7.

Adverse ReactionMetformin hydrochloride
tablets
Monotherapy
(n=141)
              Placebo              
              (n=145)              
% of Patients
Diarrhea53.211.7
Nausea/Vomiting25.58.3
Flatulence12.15.5
Asthenia9.25.5
Indigestion7.14.1
Abdominal Discomfort6.44.8
Headache5.74.8

* Reactions that were more common in metformin hydrochloride tablets – than placebo-treated patients.

Diarrhea led to discontinuation of study medication in 6% of patients treated with metformin hydrochloride tablets. Additionally, the following adverse reactions were reported in ≥1.0 to ≤5.0% of metformin hydrochloride tablets patients and were more commonly reported with metformin hydrochloride tablets than placebo: abnormal stools, hypoglycemia, myalgia, lightheaded, dyspnea, nail disorder, rash, sweating increased, taste disorder, chest discomfort, chills, flu syndrome, flushing, palpitation.

Cholestatic, hepatocellular, and mixed hepatocellular liver injury have been reported with postmarketing use of metformin.

Please note: hypoglycemia is not an expected adverse reaction because metformin hydrochloride does not directly stimulate insulin release.

Pediatric Patients

In clinical trials with metformin hydrochloride tablets in pediatric patients with type 2 diabetes, the profile of adverse reactions was similar to that observed in adults.

Side Effects for Women

Mayo Clinic states that in some cases, metformin can cause premenopausal women who do not menstruate to have periods. If this is the case for you, talk to your prescribing physician about potential side effects of metformin, as well as alternative treatments and medications.

Side Effects for Men

According to a 2016 study, metformin can lead to a “significant reduction” in sex drive and testosterone levels, as well as erectile dysfunction due to low testosterone levels in men with type 2 diabetes mellitus. If you are concerned about potential side effects of metformin, talk with your prescribing physician about alternative treatments and medications.

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