Can I Take Metronidazole on My Period?

By Nicholas White

Menstruation is a natural process in a woman’s life and its regularity is usually an indicator of normal body functioning. However, there are various factors, including the use of antibiotics, that can change the menstrual cycle.

Antibiotics, such as Metronidazole (Flagyl), are powerful drugs used to fight bacterial infections. They can affect the body’s normal microflora, which can, in turn, disrupt hormonal background and ovarian function.

Some studies indicate the possibility of menstrual changes as a result of taking Metronidazole. In particular, women sometimes report a delay in menstruation after taking the antibiotic, as well as heavier or shorter periods of bleeding.

What Is Metronidazole?

Metronidazole is a well-known bactericidal antibiotic. It penetrates the cell wall of bacteria, disrupts the DNA structure, and inhibits DNA synthesis in some microorganisms. The medication is active against:

Obligate anaerobes (but it is not active against facultative anaerobic and aerobic bacteria);

Some protozoan parasites (for example, Trichomonas vaginalis, Entamoeba histolytica, Giardia intestinalis).

Metronidazole is used primarily to treat infections caused by obligate anaerobes, often in combination with other antimicrobials. It is the medicine of choice for bacterial vaginosis (BV). However, it also has many other clinical indications. Read more information about this in the Common Uses of Flagyl section below.

What Is a Period?

Menstruation (period) is the monthly discharge of blood from the uterus in women, caused by the rejection of the uterine lining in the absence of fertilization of the egg. The first menstruation begins during puberty (at 12-14 years) and accompanies a woman until menopause (45-55 years).

The process begins when the hypothalamus begins to produce special hormones – neurohormones that stimulate the pituitary gland. Under the influence of pituitary hormones, a follicle containing an egg matures in the ovary. The follicle promotes the production of female sex hormones – estrogens. At this time, the level of the hormone progesterone is quite low.

Having matured, the follicle ruptures, and the egg is released into the abdominal cavity – this is the process of ovulation. At the site of the ruptured follicle, a corpus luteum forms. It begins to secrete the hormone progesterone, which, in turn, marks the luteal phase of the menstrual cycle. As the follicle matures, the amount of mucus in the cervical canal increases and reaches a maximum during ovulation.

Under the influence of estrogen and progesterone, the lining of the uterus thickens in preparation for receiving a fertilized egg. If fertilization does not occur, the egg dies, which is accompanied by the release of blood from the uterus – menstruation. Menstrual bleeding lasts 3-7 days, after which the cycle repeats.

Can Flagyl be Taken During Menstruation?

Metronidazole is put up for sale in different forms: tablets, solutions for infusion, vaginal suppositories, vagina gel, and gel for external use. Regardless of the form used, it is recommended to continue taking the drug even if menstruation begins during treatment since menstruation is not a contraindication to the use of Flagyl. Interrupting the treatment cycle is an irrational approach that not only harms the patient but also contributes to the emergence of antibiotic resistance.

Menstrual Cycle and Metronidazole

Let’s consider how menstruation affects the use of Metronidazole and how Metronidazole in turn affects menstruation.

How does the menstrual cycle affect the use of Metronidazole

The menstrual cycle does not have an effect on Metronidazole and does not reduce the effectiveness of treatment. Therefore, you can safely continue taking the medicine during your period. The only thing is that some inconvenience may arise when using Metronidazole vaginal (suppositories or gel through an applicator tube).

Can Metronidazole affect the menstrual cycle?

Practice shows that Flagyl can lead to menstrual irregularities, affect the duration and intensity of menstruation. But period disruption is not caused by the antibiotic itself, but primarily by the infection for which it is used. Illness is stress for the body, known to be a common cause of menstrual disorders.

There is another explanation for violations in the menstrual cycle while taking Flagil. The health of a woman who has contracted the infection has deteriorated, but she is forced to use bacterial drugs that further weaken the body. As a result, menstrual disorders may occur as a negative response of a weakened body.

As for preventive medications, which are often prescribed after surgery, a menstrual condition may be associated with hormonal imbalance.

Common Uses of Flagyl

The medical indications for taking Flagyl are quite wide. Check out the list:

  • Infectious and inflammatory diseases caused by microorganisms sensitive to Metronidazole, or protozoan infections: extraintestinal amebiasis (including amoebic liver abscess disease), intestinal amebiasis (amoebic dysentery), trichomoniasis;
  • Infections caused by Bacteroides spp. (including B. fragilis, B. ovatus, B. thetaiotaomicron, B. distasonis, B. vulgates), bone and joint infections, central nervous system infections (including meningitis, brain abscess), bacterial endocarditis, pneumonia, empyema and lung abscess, sepsis;
  • Infections caused by Clostridium spp., Peptococcus niger, Peptostreptococcus spp.: abdominal infections (peritonitis, liver abscess), infections of the pelvic organs (endometritis, abscess of the fallopian tubes and ovaries, infections of the vaginal vault);
  • Antibiotic-associated pseudomembranous colitis;
  • Gastritis or duodenal ulcer associated with Helicobacter pylori (as part of complex therapy);
  • Crohn’s disease;
  • Prevention of postoperative complications.

Can Metronidazole be used to treat menstrual-related conditions?

Considering that Metronidazole is effective against many anaerobic bacteria/protozoa and copes well with infections of the pelvic organs, including endometritis, abscess of the fallopian tubes and ovaries, infections of the vaginal vault, etc., it can be used to treat menstrual-related conditions associated with these diseases.

Dosage and Administration

The dose of Metronidazole varies depending on the age, condition of the patient, individual characteristics of the body, and the form of the drug. So, feel free to talk to your doctor and pharmacist about what dose is right for you.

If you take Metronidazole tablets by mouth, the recommended dose is 500 mg (2 tablets) 3 times a day. If an infusion solution is used to treat infections caused by anaerobic microorganisms, 500 mg (100 ml of 0.5% solution) is usually prescribed intravenously every 8 hours.

Vaginal suppositories are used 2 times a day. The recommended dose of Metronidazole gel for intravaginal use is 5 g (1 full applicator) 2 times a day (morning and evening). The gel for external use is applied in a thin layer to previously cleansed affected areas of the skin 2 times a day, morning and evening, avoiding contact with the eyes, lips, and nasal mucous membranes.

The treatment cycle duration should not exceed 7-10 days.

How long should Metronidazole be taken for menstrual-related conditions?

Metronidazole for menstrual-related conditions should be taken as long as prescribed by your doctor. Treatment usually lasts about 10 days.

Possible Side Effects of Metronidazole

Metronidazole, like any other medicine, can cause side effects. Therefore, during treatment, try to take care of yourself especially carefully. If you experience an allergic reaction, burning mouth, nausea, vomiting, abdominal pain, headache, etc. stop using the antibiotic and contact your doctor.

The medicine can interact with alcohol, so drinking alcoholic beverages during the treatment cycle is prohibited.


Individual reactions to taking the antibiotic Flagyl may vary. Some women experience changes in their menstrual cycle. Most often, this is not due to the antibiotic itself, but to the infection for which it is used, or an imbalance in the body’s hormonal levels.


Can you use BV medicine while on your period?

You can use medication for bacterial vaginosis during your period.

Does Metronidazole affect bleeding?

Some women report heavier or shorter menstrual bleeding while taking Metronidazole. This is usually caused by hormonal imbalance and infection in the body, rather than by taking the antibiotic.

Should I wear a pad with Metronidazole?

You should wear a pad if Metronidazole treatment coincides with your menstrual period.

What not to use when taking Metronidazole?

Drinking alcoholic beverages during treatment with Metronidazole is strictly prohibited, as this can cause severe side effects in the body.