Should Girls Under 18 Be Starting Their Period???

By Dr Olivia Naturals Support • June 20, 2024

Reaching the age of 18 without having started your period can be concerning and might leave you wondering about the underlying reasons and what steps you should take next. While it's essential to remember that everyone's body is different, and there can be a wide range of normal, it's equally important to address potential health issues that could be causing this delay.

Understanding Menarche and Menstrual Health

Menarche, the first occurrence of menstruation, typically happens between ages 12 and 15. However, it can occur as early as age 8 or as late as 16. When menarche has not occurred by age 18, it is classified as primary amenorrhea, a condition that warrants further investigation to determine the underlying causes and appropriate interventions.

Potential Causes for Delayed Menarche

1. Low Body Weight

One of the most common reasons for a delay in the onset of menstruation is low body weight. Being underweight can disrupt the normal production of hormones necessary for menstruation. This can be due to various reasons including eating disorders such as anorexia nervosa, excessive physical activity, or other health conditions that impact weight.

2. Hormonal Imbalances

Hormonal imbalances can also play a significant role. Hormones such as estrogen and progesterone regulate the menstrual cycle, and imbalances in these hormones can prevent periods from starting. Conditions such as polycystic ovary syndrome (PCOS), thyroid disorders, and other endocrine system disorders can disrupt hormone levels.

3. Genetic Factors

Genetics can influence the age at which menstruation begins. If there is a family history of late menarche, it might simply be a genetic trait. However, it's important to rule out other causes to ensure there are no underlying health concerns.

4. Chronic Illnesses

Chronic illnesses such as diabetes, celiac disease, or inflammatory bowel disease can also affect the onset of menstruation. These conditions can impact overall health and nutrition, which in turn affects hormonal balance and reproductive health.

5. Structural Issues

Occasionally, there may be structural issues within the reproductive system, such as congenital abnormalities of the uterus, cervix, or vagina, that can prevent menstruation. These issues are less common but should be considered if other causes are ruled out.

First Steps to Take

If you are 18 and have not yet started your period, it’s crucial to consult with a healthcare provider. Here are the steps you can expect in the diagnostic process:

1. Medical History and Physical Examination

Your doctor will start by taking a detailed medical history and conducting a physical examination. They will ask about your growth and development, diet, exercise habits, family history, and any symptoms you may be experiencing. The physical exam may include an assessment of your secondary sexual characteristics, such as breast development and pubic hair growth.

2. Hormone Testing

Hormone tests are essential in determining if there are imbalances that might be preventing menstruation. These tests typically include measuring levels of:

  • Estrogen and Progesterone: Key hormones in regulating the menstrual cycle.
  • Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH): These hormones stimulate the ovaries and play a crucial role in reproductive health.
  • Thyroid Hormones: Since thyroid disorders can affect menstrual cycles.
  • Prolactin: High levels can inhibit menstruation.

3. Blood Work

General blood work can provide a broader picture of your overall health and identify any other potential issues, such as nutritional deficiencies, that might be affecting your menstrual health.

4. Cycle Mapping

Cycle mapping is a more in-depth approach to understanding your hormonal fluctuations throughout the menstrual cycle. Done by companies such as Dutch and Precision Analytics, this test involves taking multiple samples over a menstrual cycle (or an expected cycle) to track hormone levels over time. This can offer a comprehensive view of your hormonal patterns and identify any abnormalities that might be causing your amenorrhea.

Treatment and Management

Once the underlying cause of delayed menarche is identified, your healthcare provider will recommend a treatment plan tailored to your specific needs. This might include:

1. Nutritional and Lifestyle Changes

If being underweight is the issue, working with a nutritionist to achieve a healthy weight can help. Incorporating a balanced diet rich in essential nutrients and maintaining a healthy exercise routine can support overall health and potentially trigger the onset of menstruation.

2. Hormone Therapy

In cases of hormonal imbalances, hormone therapy may be prescribed to regulate your menstrual cycle. This could include birth control pills or other hormone replacement therapies to correct the imbalance and induce menstruation.

3. Medications for Underlying Conditions

If a thyroid disorder, PCOS, or another medical condition is identified, specific medications to manage these conditions will be necessary. Proper management of these conditions can help restore normal menstrual function.

4. Addressing Psychological Factors

Stress and psychological factors can also impact hormonal balance and menstruation. Counseling or therapy might be recommended to address any underlying psychological issues contributing to delayed menarche.

Long-Term Considerations

It’s important to monitor your menstrual health over the long term, even after treatment has started. Regular follow-ups with your healthcare provider can ensure that your menstrual cycle remains regular and that any new issues are promptly addressed.

1. Bone Health

Delayed menarche can impact bone health, as estrogen is crucial for bone density. Ensuring adequate calcium and vitamin D intake, along with regular weight-bearing exercise, is important for maintaining bone health.

2. Fertility

While delayed menarche doesn’t necessarily impact future fertility, it’s important to address any underlying conditions that could have long-term reproductive implications. If you plan to have children in the future, discussing this with your healthcare provider can help you understand any potential issues and plan accordingly.


Reaching 18 without starting your period can be concerning, but it’s a situation that many have faced and successfully managed. Understanding the potential causes, seeking appropriate medical advice, and following a tailored treatment plan can help you achieve regular menstrual health. Remember, every individual is unique, and what’s important is finding the right approach for your specific needs. Don’t hesitate to reach out to healthcare professionals who can guide you through this process and support you in achieving optimal health.