What Are Commonly Used Fertility Medications and How Do They Change My Cycles?

What Are Commonly Used Fertility Medications and How Do They Change My Cycles?

When you are in the fertility world, you may often hear about different fertility drugs in chat rooms, in emails or even your google searches! We are breaking down some of the most common first-line interventions including Letrozole/Femara, Clomiphene/Clomid and Medroxyprogesterone/Provera and discussing how their use can affect your cycles.

Types of Fertility Medications


Letrozole, (brand name Femara), is a drug called an aromatase inhibitor. This means that it blocks the conversion of various hormones into estrogen. The reason it works for fertility is that letrozole essentially makes your brain think that there isn’t enough estrogen present, so it triggers your brain (pituitary) to make more FSH (follicle stimulating hormones) which in turn, talks to your ovaries and stimulates your ovaries to produce an egg!

It typically is only used for around 5 days at the beginning of your cycle and then discontinued, as it simply acts as a trigger for follicle formation. The hope is that the drug will help trigger follicle creation. Then, the egg will continue to grow, mature and be released at ovulation! Pretty clever, right?


Clomid, or clomiphene citrate, is an estrogen modulator that is similar to Letrozole, in that it is an ovulation inducer. Clomid helps stimulate the ovaries to produce eggs by blocking estrogen receptors in the brain and makes the brain think there is no estrogen around. The brain then secretes follicle stimulating hormone (FSH) and luteinizing hormones (LH), which promotes follicle development. A potential disadvantage of clomid is the thinning of the endometrial lining, due to the blockage of estrogen receptors in the endometrium, preventing endometrial thickening. Another is a change in cervical mucus consistency. These are not as commonly seen with letrozole.


Now, if you’ve heard of letrozole, you’ve probably heard of Provera! Many times this drug is used to induce a period before beginning Letrozole or Clomid if someone hasn’t had a cycle in some time.

Provera is the brand name for medroxyprogesterone, a synthetic version of progesterone that triggers a period after it has stopped. It mimics what naturally happens in the luteal phase of the menstrual cycle: a buildup and then swift drop off of progesterone that triggers the start of menstruation.  However, since in this case, it’s not actually progesterone, but rather a synthetic form of progesterone that binds very tightly to receptors, its absence is very much noticed! This is how some physicians will also test for something called Hypothalamic amenorrhea, a condition in which the pituitary is not responding to feedback.  You may have also heard  menstrual periods after Provera referred to as a “withdrawal bleed”.

A snap shot of your hormone

Fertility Medication and Tracking Your Fertility

Enough pharmacology, let’s take a look how these drugs can change your menstrual cycle observations!

Now, this may leave your wondering, how do these medications change my cycle and test results?

Ovulation Testing

Because letrozole and clomid are going to increase your FSH and LH, if your body is properly responding to the medication, you should see your LH levels begin to spike and then peak, just as they would with a normal ovulation!

These medications are essentially just encouraging your body to ovulate as it should normally. Typically the drug will be used days 3-7 of the menstrual cycle, and LH testing should begin as early as day 8 to ensure the LH spike isn’t missed. The only difference you may see is, depending on what day of your cycle you begin your Letrozole or Clomid, your ovulation may be sooner or later than you are used to.

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Cervical Mucus Tracking

With Clomid, you may notice some changes in your cervical mucus. As discussed above, Clomid blocks estrogen, and estrogen is the hormone that helps create the lovely egg-white consistency fertile mucus! When estrogen levels are disrupted, this changes the consistency of your cervical mucus.

Progesterone and BBT Tracking

When using Provera, it’s important to understand that it mimics natural progesterone. So, if you take a progesterone test while taking Provera, it can cause a false positive. Additionally, research has shown that synthetic progesterone still has a thermal effect in the body. So, you can expect your BBT to increase while taking the prescription and swiftly drop off when you stop taking the medication, just as in a typical menstrual period.

Medications can get confusing quickly; don’t be afraid to ask your practitioner any questions you may have before beginning any fertility treatments. There are often many options available, and voicing your concerns and desires can help your fertility specialist find the ideal treatment plan, just for you!

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