Can STIs delay your period?

Your period is late – even though you’re sure you’re not pregnant? Maybe you recently had unprotected sex or are noticing other changes in your body. The question quickly arises: Could a sexually transmitted infection (STI) be the reason for your delayed period? While we usually think of hormones or stress when it comes to menstrual irregularities, infections can also play a role.

In this article, you’ll learn whether and how certain STIs can affect your period, which infections may be relevant, and what you should do if you suspect an STI?

Table of contents

• How long does a normal menstrual cycle last?
• What is an STI?
• Can STIs delay your period – and how?
• What are other causes of a delayed period?
• When is an STI test advisable?

How long does a normal menstrual cycle last?

An average menstrual cycle lasts about 28 days, but it can vary individually between 21 and 35 days. The duration is counted from the first day of your period to the day before your next bleeding starts. Mild fluctuations are normal, especially in young people or during hormonal changes. However, if your period regularly skips or shifts significantly, this may indicate an underlying health issue – such as a hormonal disorder or an infection (MayoClinic, 2023).

What is an STI?

STI stands for “sexually transmitted infection.” These are infections primarily transmitted through unprotected sexual intercourse – vaginal, anal, or oral. In some cases, transmission can also occur through blood or from mother to child during birth.

STIs are caused by bacteria, viruses, or parasites and can affect both men and women. Many infections initially cause no symptoms, which means they can easily be passed on to others unnoticed. If left untreated, however, they can lead to serious health consequences – for example, affecting fertility or the immune system.

If symptoms do occur, they may include:

• Unusual vaginal or penile discharge
• Pain or burning during urination
• Lower abdominal pain
• Spotting between periods
• Pain during intercourse

Source: NHS, 2024

Can STIs delay your period – and how?

Sexually transmitted infections (STIs) can indirectly affect your menstrual cycle – especially if left untreated and they spread into the pelvic area. The resulting inflammation, for example in the uterus or fallopian tubes, can disrupt hormonal processes and lead to a delayed or missed period. Psychological stress related to an infection – such as worry about possible transmission – can also delay your cycle. Two infections are particularly often associated with menstrual disruptions:

Chlamydia

Chlamydia is usually asymptomatic but can spread upwards if left untreated and cause what’s known as Pelvic Inflammatory Disease (PID). This can disrupt the hormonal regulation of your cycle. Consequences may include:

• A delayed or missed period
• An irregular menstrual cycle
• Additional symptoms like abdominal pain or spotting between periods

Gonorrhea

Gonorrhea can also cause inflammatory processes in the pelvic area, interfering with egg maturation and ovulation. In such cases, those affected may report:

• A significantly delayed period
• Missed periods over multiple cycles
• Lower abdominal pain during the expected cycle phase

Although sexually transmitted infections are not among the most common causes of delayed periods, they should not be ruled out if there are risk factors such as unprotected sex or noticeable symptoms.

Sources: Cleveland Clinic, 2024; Cleveland Clinic, 2023

What are other causes of a delayed period?

Not every delayed period is caused by an infection. There are many other, often more harmless reasons, including:

• Hormonal changes (e.g., after stopping the pill)
• Severe weight loss or underweight
• Intense physical exercise or strain
• Psychological stress
• Thyroid disorders
• Polycystic ovary syndrome (PCOS)
• Menopause (in older women)

A one-time missed period is usually harmless. However, if irregularities occur repeatedly, a medical evaluation is recommended (Cleveland Clinic, 2023).

When is an STI test advisable?

Testing for sexually transmitted infections is recommended in many situations – not only if you have acute symptoms. It’s especially advisable if:

• You’ve had unprotected sex
• You have changing or new sexual partners
• Your period is late and other causes (e.g., pregnancy or hormonal shifts) have been ruled out
• You experience symptoms like discharge, burning while urinating, abdominal pain, or spotting
• Your menstrual cycle suddenly becomes irregular or unusually heavy/painful
• Your partner has tested positive for an STI
• You’ve had an STI in the past
• You want to make sure no infection has gone unnoticed
• You want to monitor your sexual health regularly and preventively

Source: CDC, 2025

A home STI test from Homed-IQ allows you to get tested discreetly and conveniently from the comfort of your home. The samples are professionally analyzed in a laboratory, and you receive your results online – safely, confidentially, and without a doctor’s visit.

References

Getting Tested for STIs | STI. (2025, January 31). CDC. Retrieved July 21, 2025, from https://www.cdc.gov/sti/testing/index.html

Irregular Periods (Abnormal Menstruation): Causes & Treatment. (n.d.). Cleveland Clinic. Retrieved July 21, 2025, from https://my.clevelandclinic.org/health/diseases/14633-abnormal-menstruation-periods

Menstrual cycle: What’s normal, what’s not. (2023, April 22). Mayo Clinic. Retrieved July 21, 2025, from https://www.mayoclinic.org/healthy-lifestyle/womens-health/in-depth/menstrual-cycle/art-20047186

Sexually transmitted infections (STIs). (2024, May 13). NHS. Retrieved July 21, 2025, from https://www.nhs.uk/conditions/sexually-transmitted-infections-stis/

What To Know About Bleeding Between Periods. (2024, March 12). Cleveland Clinic Health Essentials. Retrieved July 21, 2025, from https://health.clevelandclinic.org/when-should-you-worry-about-spotting-between-periods