Can STIs affect your period?

There are many factors that can affect and disrupt a woman’s menstrual cycle. One rarely-discussed factor that can affect your period is an STI.

Read on to find out how your period might be affected by an STI you may not know you have.

STIs can affect many aspects of your overall health. Protect yourself with a comprehensive health screen at a clinic near you.

What are STIs?

Sexually transmitted infections (STIs) are infections that you get primarily from sex. This includes vaginal, anal, and oral sex, but it can also include things like foreplay, genital touching, and sharing sex toys.

These bacterial, viral, and parasitic infections easily go undetected since most infections don’t cause symptoms. You can have an infection like Chlamydia or HIV for weeks, months, or even years and not know it.

When they go untreated, STIs can cause serious damage to your health. Depending on the infections, they can cause infertility and ectopic pregnancies, cause damage to major organ systems like the heart, liver, brain, eyes, and bones, and raise your risk of getting certain cancers.

STIs can also affect your health in other ways, causing changes to systems that you may not expect.

One of these ways is how they can affect your menstrual cycle.

How does my period work?

Menstruation, commonly known as a period, is a natural process that occurs in the female reproductive system. It involves the shedding of the uterine lining, which exits the body through the vagina.

This cycle typically lasts between 24 and 38 days, with menstruation lasting from three to seven days. Hormones such as oestrogen and progesterone regulate the menstrual cycle, which prepares the body for potential pregnancy each month.

 If fertilisation does not occur, the thickened uterine lining is no longer needed and is expelled during menstruation.

What STIs can affect my period?

As you can imagine, many STIs can affect your period.

Chlamydia

Chlamydia, a common STI caused by the bacterium Chlamydia trachomatis, is also the most common STI that causes irregularity of a woman’s menstrual cycle.

While Chlamydia itself may not directly cause changes in the timing of periods, it can lead to intermenstrual bleeding, which is bleeding that occurs between regular menstrual periods. One of the primary concerns is the development of PID, which occurs when the infection spreads to the uterus, fallopian tubes, or ovaries. PID can cause irregular periods, heavier menstrual bleeding, and increased menstrual pain. Additionally, the inflammation and damage caused by the infection can disrupt the normal functioning of the reproductive organs, leading to these menstrual irregularities.

Gonorrhoea

Gonorrhoea, caused by the bacterium Neisseria gonorrhoeae, can significantly impact a woman’s menstrual cycle. Gonorrhoea can also result in intermenstrual bleeding, which is bleeding that occurs between regular menstrual periods.

Gonorrhoea can also lead to PID if left untreated, causing irregular periods, heavier menstrual bleeding, and increased menstrual pain.

Trichomonas

Trichomonas, caused by the protozoan parasite Trichomonas vaginalis, can affect a woman’s menstrual cycle in several ways.

This infection often leads to symptoms such as vaginal itching, burning, and a foul-smelling discharge, which can cause discomfort and irritation. These symptoms can be particularly bothersome during menstruation, potentially exacerbating menstrual pain and discomfort. Additionally, Trichomonas can cause inflammation of the genital tract, which may lead to irregular bleeding or spotting between periods.

Mycoplasma

Mycoplasma genitalium (Mgen) is another bacterial STI that can affect a woman’s menstrual cycle.

In some cases of Mgen, there is inflammation and irritation, and this can disrupt the normal menstrual cycle, resulting in irregular periods or spotting between periods. Additionally, the infection can cause PID if it spreads to the uterus, fallopian tubes, or ovaries, further affecting menstrual regularity and causing increased menstrual pain.

HIV

HIV can significantly impact a woman’s menstrual cycle due to its effects on the immune system and overall health. The virus can cause hormonal imbalances that disrupt the regularity of menstrual periods.

Women living with HIV may experience irregular periods, heavier or lighter bleeding, and increased menstrual pain, mostly in those who have not been diagnosed and have high levels of free vrius in their blood, and low defenses. In some cases, HIV can lead to amenorrhea, which is the absence of menstrual periods. These changes are often linked to the body’s response to the infection and the stress it places on the immune system.

Additionally, the medications used to manage HIV can have side effects that affect the menstrual cycle. Some antiretroviral drugs may cause hormonal fluctuations, leading to irregular periods or changes in menstrual flow. However, the modern types of HIV medication will normally restore balance tot he woman’s immunity and menstrual cycle.

The overall health challenges associated with managing HIV, such as stress, weight loss, and nutritional deficiencies, can further contribute to menstrual irregularities.

Syphilis

Syphilis, caused by the bacterium Treponema pallidum, can have various effects on a woman’s menstrual cycle, particularly if left untreated.

The infection progresses through different stages—primary, secondary, latent, and tertiary—each with distinct symptoms. During the secondary stage, Syphilis can cause symptoms such as skin rashes, swollen lymph glands, and mucous membrane lesions. These symptoms can lead to increased stress and hormonal imbalances, which may disrupt the menstrual cycle, causing irregular periods or changes in menstrual flow.

In the later stages, untreated Syphilis can cause severe health complications that further impact menstrual health. Extremely advanced cases of Syphilis can cause major organ damage, involving any part of the female reproductive system.

Hepatitis B and Hepatitis C

Hepatitis B can affect a woman’s menstrual cycle primarily through its impact on liver function. This tends to occur in the rare situation of having chronic Hepatitis B, when the infection didn’t resolve properly.

The liver plays a crucial role in metabolising hormones, including those that regulate the menstrual cycle. When the liver is inflamed or damaged due to Hepatitis B, it can lead to hormonal imbalances that disrupt the regularity of menstrual periods.

Hepatitis C similarly affects the menstrual cycle by disrupting liver function and hormone regulation. Undetected cases of Hepatitis C with consequent damage are mor common than Hepatitis B.

The liver is essential for processing oestrogen and progesterone, the hormones that control the menstrual cycle. Women with Hepatitis C may experience irregular periods, missed periods, or changes in menstrual flow. The chronic nature of Hepatitis C can lead to significant liver damage over time, exacerbating these menstrual irregularities.

Bacterial vaginosis

While it isn’t technically considered an STI, bacterial vaginosis (BV) is a common vaginal infection caused by an imbalance in the natural bacteria found in the vagina.

While BV does not directly affect the menstrual cycle, it can cause symptoms that may be more noticeable during menstruation. For instance, the hormonal changes and the slightly alkaline nature of menstrual blood can exacerbate BV symptoms, leading to increased vaginal discharge and a stronger odour.

Am I more likely to get an STI during my period?

If you’re having sex without a condom during your period, you may be putting yourself at risk of getting an STI. You may also be at risk of getting or passing on blood-borne STIs, like HIV, Hepatitis B, and Hepatitis C.

People who report having sex during their period were more likely to report having a history of STIs. Also, changes during your menstrual cycle may make it harder for your immune system to fight infections.

What else might cause period changes?

Here are some factors that can affect a woman’s menstrual cycle that aren’t related to STIs:

1. Diseases in the female reproductive tract: Any diseases that can affect the anatomy of organs essential to normal menstruation can cause an irregular cycle or unexpected bleeding (diseases of the ovaries Fallopian tubes, uterus, and vagina).
2. Disease of the hormone producing organs: Diseases of the ovaries, or even diseases of the pituitary gland, the part of the brain that regulates sex hormone, will affect the menstrual cycle.
3. Medication: There are many common medication that can affect the menstrual cycle, like antidepressants or anti-inflammatory tablets.
4. Stress: High levels of stress can disrupt the hormonal balance, leading to irregular periods or missed periods.
5. Diet and nutrition: Poor diet or sudden changes in eating habits can affect menstrual cycles. Nutrient deficiencies, such as low iron or magnesium, can contribute to irregularities.
6. Exercise: Excessive physical activity or sudden changes in exercise routines can impact menstrual regularity.
7. Weight changes: Significant weight loss or gain can affect hormone levels and disrupt the menstrual cycle.
8. Thyroid disorders: Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) can cause menstrual irregularities.
9. Travel: Changes in time zones and routines can temporarily affect the menstrual cycle.
10. Sleep: Poor sleep patterns or changes in sleep routines can impact hormonal balance and menstrual regularity.
11. Addiction to drugs or alcohol: Although occasional use of drugs and alcohol doesn’t tend to alter a woman’s menstrual cycle, overuse has seen to be related to irregular cycles or even amenorrhoea (periods completely stopping)

Final thoughts

If you’re concerned that an STI is disrupting your menstrual cycle, you should get tested. Click the button below to book an STI test at a sexual health clinic near you.  

Don’t leave your sexual health to chance. Get tested with Better2Know today.

This article has been medically reviewed by Dr. Steve Chapman, 16/07/2025.