What Is the Follicular Phase of the Menstrual Cycle?

The follicular phase is the first half of your menstrual cycle, starting on day 1 of your period and ending at ovulation. During this phase, your ovaries produce follicles containing immature eggs, one egg matures for release, and your uterine lining thickens to prepare for potential pregnancy. The late follicular phase coincides with your fertile window, making it the best time to conceive.

Your menstrual cycle is made up of two phases: the follicular phase and the luteal phase. Throughout each phase, changing hormone levels trigger different functions as your body busily prepares for a potential pregnancy.

Throughout each phase, changing hormone levels trigger different functions as your body busily prepares for a potential pregnancy. Then, it starts the cycle over again if you don’t get pregnant. 

The follicular phase starts on the first day of your period and lasts until you ovulate. During the follicular phase, your body prepares a follicle (an immature egg) to be released during ovulation. 

Here’s a closer look at what’s happening with your body during the follicular phase, how long this phase may last, signs you’re in this phase, and whether you can get pregnant during the follicular phase.

What is the follicular phase?

The follicular phase, sometimes called the “proliferative phase,” is one of the two phases of your menstrual cycle. The follicular phase starts on the first day of your period, also known as day one of your cycle, and lasts until you ovulate. 

During the follicular phase, a few different things are happening in your body, mostly revolving around your ovaries and eggs: 

• You get your period
• Your ovaries produce follicles
• An egg matures and prepares to be released during ovulation
• Your uterine lining (or endometrium) thickens

You get your period

Your period is the sign that your menstrual cycle has restarted, and it’s also the sign that your follicular phase has begun. During your period, you shed the lining of your uterus, which was thickened during your previous menstrual cycle in preparation for a potential pregnancy. Your follicular phase continues past the last day of your period. 

Your ovaries produce follicles

At the same time as your period, the hypothalamus and the pituitary gland—two structures in your brain that are crucial to hormone production—get involved. Your hypothalamus sends a signal to your pituitary gland to begin producing follicle-stimulating hormone (FSH). In response to rising FSH levels, your ovaries start producing follicles—pretty straightforward, given the name “follicle-stimulating hormone.” Each follicle houses an immature egg, which grows as the follicular phase continues.

An egg matures and prepares to be released during ovulation

Soon, one follicle becomes the dominant follicle. The other follicles start to deteriorate and are eventually reabsorbed back into your body. In the dominant follicle, meanwhile, an egg continues maturing until it reaches full maturity.

Your uterine lining (or endometrium) thickens

The maturing egg releases estrogen, making overall estrogen levels rise. Rising estrogen stimulates your uterine lining to grow thick and rich in nutrients. A thickened endometrium is necessary for a fertilized egg to be able to implant in the uterus and for pregnancy to occur.

These rising estrogen levels also send signals to your hypothalamus and your pituitary gland to decrease FSH levels and increase luteinizing hormone (LH) levels, a hormone crucial to ovulation. 

>>RELATED: What Are Normal Estrogen Levels (And How Do I Measure Mine)?

When LH surges (meaning hits its peak level), ovulation is triggered, the mature egg is released from its follicle, and the follicular phase ends. Ovulation marks the start of the luteal phase, the next phase of your cycle.

How long is the follicular phase?

Just like your cycle length, the length of your follicular phase can vary, too—from person to person and from month to month. 

The length of your follicular phase is determined by how long it takes for a given follicle to mature into an egg. 

When the maturing process takes longer, the follicular phase is longer and your cycle is longer. On the flip side, the follicular phase, and your cycle, are shorter when it takes less time for a follicle to mature. The length of your follicular phase also changes with age.

Cycles can be anything from 21 to 35 days long and still fall within a normal range, and the follicular phase varies along with that. The follicular phase can range from 10 to 16 days. 

Keep in mind that follicular phase length changes, meaning it’s entirely possible to have short, long, and mid-range follicular phases from one cycle to the next. 

What does it mean if the follicular phase is long?

If your follicular phase lasts longer than 16 days, it can be considered long. This doesn’t necessarily mean much, aside from the fact that your overall cycle is long, too.

Your follicular phase may be longer if you’ve used birth control pills for a long time, or if you were on the pill recently. 

If your follicular phase is longer, it doesn’t impact your fertility or mean that you’re less likely to become pregnant.

What does it mean if the follicular phase is short?

If your follicular phase lasts less than 10 days, it’s considered short.

When the follicular phase is short, the egg released during ovulation may not have had enough time to fully mature, which also means it may not be able to be fertilized by sperm. This can impact the chances of conceiving in a given cycle, or overall if your follicular phases are consistently short.

In other words, a shorter follicular phase may make it harder for you to get pregnant.

A shorter follicular phase may also be a sign that you’re entering perimenopause, or the transition into menopause, as the follicular phase shortens near menopause.

How do you know if you’re in the follicular phase?

There are a few ways to know that you’re in the follicular phase of your cycle. 

Follicular phase symptoms

The most telltale sign of this phase is your period. During the follicular phase, you may experience symptoms typically associated with your period, like:

• Bloating
• Cramps
• Nausea
• Breast tenderness
• Lower back pain
• Headaches
• Tiredness
• Mood swings

>>RELATED: 8 Symptoms That Could Be Related to Your Period - And How to Get Relief

Basal body temperature

Your basal body temperature (BBT), or your body temperature when you’re fully at rest, can also indicate which phase of your cycle you’re experiencing. BBT is at its lowest during the follicular phase, typically ranging from 97°F to 98°F. BBT increases following ovulation and the start of the luteal phase. 

To track how your BBT changes throughout your cycle, take your temperature in the morning, right when you wake up and before you get out of bed. After a few cycles-worth of daily temperature readings, you may be able to use your BBT to track the phases of your cycle and find when you’re most fertile.

Hormone-based cycle tracking

The final and most accurate way to know you’re in your follicular phase is to track your cycle, specifically through changes in your hormones. Regular cycle tracking works on the assumption that you follow a 28-day menstrual cycle, when the reality is that many people don’t fall into that standard—and that’s completely normal!

Instead, by measuring key hormones of the menstrual cycle, like LH, estrogen, and progesterone, you can get a clear picture of when your unique hormone trends and cycle timing. For example, tracking estrogen can help you understand when your body is ready to release the mature egg, and tracking LH can show you when you’re experiencing the LH surge and are about to ovulate.

Can you get pregnant during the follicular phase?

Yes, you can get pregnant during the follicular phase. 

More specifically, the late follicular phase is the time when you should have sex if you’re trying to conceive, as this part of your cycle corresponds with your fertile window.

Your fertile window is the time during your cycle when you’re most fertile – and most likely to get pregnant. At-home fertility testing kits are one tool to track your cycle phases and find your fertile window. Generally, the fertile window lasts six days: the five days leading up to ovulation, and the day after ovulation. 

This timeline means that most of your fertile window occurs during the late follicular phase, making the follicular phase the time in your cycle when you’re most likely to get pregnant. 

The follicular phase: the bottom line

There’s a lot going on in your body during the follicular phase of your menstrual cycle.

You get your period, your ovaries start producing follicles, a follicle matures into an egg to be released during ovulation, and your endometrium thickens.

The follicular phase can vary in length from cycle to cycle, depending on how long it takes for a follicle to mature. While a longer follicular phase doesn’t impact fertility, a shorter follicular phase may make it harder for you to get pregnant in a given cycle.

If you’re trying to conceive, knowing the signs of the follicular phase and tracking your menstrual cycle can be key for timing when to have sex. When all goes well, the follicular phase may just be the part of your cycle when you’re most likely to get pregnant.

Frequently Asked Questions About the Follicular Phase

What is the follicular phase of the menstrual cycle?

The follicular phase is the first half of your menstrual cycle, starting on day 1 of your period and ending when you ovulate. During this phase, follicle-stimulating hormone (FSH) triggers your ovaries to produce follicles, one egg matures, and your uterine lining thickens in preparation for pregnancy.

How long does the follicular phase last?

The follicular phase typically lasts 10-16 days, though this varies from person to person and cycle to cycle. The length depends on how long it takes for a follicle to mature into a ready-to-release egg. A 28-day cycle usually has a 14-day follicular phase.

What are the signs you're in the follicular phase?

Signs of the follicular phase include your period (early phase), increased energy levels, clearer skin, and rising basal body temperature. As you approach ovulation in the late follicular phase, you may notice clearer, stretchy cervical mucus and increased sex drive.

Can you get pregnant during the follicular phase?

Yes, especially during the late follicular phase. Your fertile window includes the 5 days before ovulation and the day of ovulation itself—all of which fall within the follicular phase. This is the best time to have sex if you're trying to conceive.

What happens if your follicular phase is too short?

A follicular phase shorter than 10 days may mean the egg didn't have enough time to fully mature, potentially making it harder to conceive. Short follicular phases can also be an early sign of perimenopause as egg quality and ovarian reserve decline.

What is the difference between follicular phase and luteal phase?

The follicular phase starts on day 1 of your period and ends at ovulation, focusing on egg maturation and preparing for pregnancy. The luteal phase starts after ovulation and ends when your next period begins, focusing on supporting a potential pregnancy through progesterone production.

Can lifestyle factors affect my follicular phase length?

Yes, several lifestyle factors can influence follicular phase length. Research shows that women with a history of miscarriage tend to have shorter follicular phases, while lifestyle factors such as recent oral contraceptive use can lead to longer follicular phases. Maintaining a balanced diet rich in vegetables, antioxidants, and healthy fats, along with moderate exercise, can support healthy follicular development and overall reproductive health.

Does exercise during the follicular phase impact fertility?

Moderate physical activity can be beneficial for fertility, especially when coupled with healthy weight management. However, excessive exercise can negatively affect your reproductive system by creating an energy imbalance that may disrupt hormone production and lead to menstrual abnormalities. During the follicular phase, as your energy levels increase with rising estrogen, you may find yourself able to handle more intense workouts like cardio and strength training.

What foods should I eat during the follicular phase to support fertility?

During the follicular phase, focus on iron-rich foods to compensate for blood loss during your period, including red meat, seafood, legumes, and green leafy vegetables. Lean proteins and complex carbohydrates like chicken, fish, brown rice, and quinoa can help support rising energy levels, while cruciferous vegetables such as broccoli and cauliflower can help balance increasing estrogen levels.

Can stress affect the follicular phase?

While stress alone does not cause infertility, psychological stress is one of several lifestyle factors that can impact fertility and overall reproductive health. Managing stress through relaxation techniques and moderate exercise may support a healthy follicular phase and improve your chances of conception.