What Phentermine Does to Your Period

Phentermine may cause irregularities in your period, resulting in a worsening of your monthly symptoms, due to its action on your hormonal levels. In this article we will describe what phentermine does to your period and how to deal with the symptoms.


It may not be registered as a phentermine adverse effect, but plenty of hearsay exists about women experiencing menstrual cycle changes while on this drug. Below is a list of symptoms reported by female Phentermine users:

  • Late periods (delayed for more than five days)
  • Missed periods (absent flow for over 40 days)
  • Early periods (appearing five or more days than expected)
  • Heavy flow or longer duration of periods
  • Light flow or shorter duration of periods
  • Incidence of spots or short bleeding in-between periods
  • Reduced number of period cycles (Oligomenorrhea, 4 – 9 periods in 12 months)
  • Increased number of period cycles (Polymenorrhea, over 17 cycles in 12 months)
  • Increased symptom severity – premenstrual syndrome (PMS), cramps, dizziness and nausea.

What these period alterations mean is that the physiological process of menstruation has been dysregulated, resulting in a changed symptom profile compared to what was the norm for you before starting phentermine.

We understand that experiencing symptoms such as these may alarm you, however, by letting you know that this is a common finding amongst female phentermine users we hope to reassure you, and also stress the importance of the phentermine forum in the provision of trusted information regarding this drug.

What is the Mechanism behind Phentermine’s Influence on Your Period?

Similarly to how phentermine has been associated to hair loss, it is believed that phentermine results in period changes indirectly, through the way in which losing weight affects hormonal levels that regulate your menstrual cycle.

Excessive weight loss, something common with phentermine use, decreases estrogen levels in the body, since this hormone is closely associated with the number of fat cells present in the organism. Lower estrogen results in the alteration of the menstruation process, which appears as period irregularities or even complete pause.

Another proposed mechanism implicates the stimulation of the sympathetic nervous system; by triggering the “fight or flight” state, reproductive hormone production decreases, resulting in the afore mentioned symptoms and signs. On the other hand, some phentermine adverse effects such as period irregularity, spotting or increased flow may be explained by the stimulating effect of the drug on the heart muscle. A heart that beats faster causes the blood flow to increase, ultimately leading in overloading the endometrium’s ‘spiral arteries’; this over activity ultimately results in more frequent periods.

Another factor leading to menstrual cycle dysregulation is malnutrition, stemming from the inability to follow a diet of adequate variance, probably because phentermine acts as an appetite suppressant. It doesn’t matter whether you work out or how much you weigh, inadequate ingestion of zinc, iron and healthy fatty acids may all affect your period and enhance the severity of period symptoms such as nausea, dizziness and cramps.

How to Cope with the Symptoms

If you haven’t been eating properly while taking phentermine, then this could be causing your period symptoms. Starting on a multivitamin supplement for the duration of your phentermine treatment, will make sure that no essential nutrients are missing from your diet, which may also aid in the resolution or dampening of the unpleasant menstrual symptoms.

As a matter of fact, by ensuring adequate ingestion of minerals and vitamins, you will also get to your weight loss goals easier, since you will be providing your body with everything it needs to keep your metabolism burning. Along with your vitamins, you should always aim for a diverse diet plan, packed with healthy food choices such as dark green leafy vegies, lean meats and also nuts and seeds that will aid you in better handling the unpleasant symptoms.

If you are in a situation where pregnancy is a possibility, you should make sure to use a birth control method, because phentermine is contraindicated in pregnancy. If you choose an oral contraceptive, then you may find that it helps you cope with the severe symptoms of menstruation, such as cramps and PMS. The birth control pill is usually prescribed by doctors to those women whose periods are accompanied with pain and heavy flow, however, it is preferable to allow at least 4 periods in on year, to maximize their chances of being fertile in the future.

By opting to not have a period on a monthly basis, you will be somewhat relieved from the adverse effects that phentermine has on your menstruation. Furthermore, fewer periods mean less symptoms associated with that time of the month, like cravings, bloating and weight gain, which ultimately will motivate you to continue taking phentermine.

Finally, if period irregularities are something you have been accustomed to, plus you have had trouble with your weight and were bothered with symptoms like cramps, fatigue, constipation, acne or infertility, then you should get screened for medical conditions such as thyroid disease and PCOS (Polycystic Ovary Syndrome), both known to affect hormonal levels.

Dealing with period irregularities and other more serious side effects is nothing to joke about, however, improving your health by following a proper diet and shedding excess weight with the help of phentermine, will aid you get past these problems eventually. Keep in mind that as you approach your weight goals, your body will get used to the modified hormonal levels, normalizing your period cycle and dampening the severity of your symptoms.

Last updated: April 10th, 2017. Bookmark the permalink.

6 thoughts on “What Phentermine Does to Your Period

  1. I suffer from heavy flow and irregular period. Not sure if Phentermine is the cause or not. Are there any other factors that causes heavy flow and irregular period?

  2. Before starting phentermine, my menstrual cycle had always been irregular. I had very long and heavy periods that lasted anywhere from 7-10 days and always experienced light spotting in between cycles. I always assumed that being over weight was the cause of my irregularity, because when I was a teenager and thinner, I didn’t have these issues.

    I started Phentermine just a couple days after starting my period, and since starting, I literally have not stopped bleeding. It’s difficult to know where my period ends and the “spotting” begins. But I can always tell when my period is about to start because I still experience cramps and PMS cravings and increased hunger. When my period starts it’s extremely heavy and there’s a lot of very large blood clots. The heavy flow only lasts 3-7 days, at which I feel the period ends, and from there it’s only light “spotting” until my next period starts. I put spotting in quotes because some days I don’t bleed at all, and then others it’s a light flow like I’m on my period.

    This is my second time being on Phentermine. The first time I was on it, I was in my early teens and only weighed 280 pounds, and I didn’t experience any menstrual differences, except maybe missing my period once or twice. This time around I was 400 at my heaviest, but right now I’m at 350. At this point in time, I haven’t brought up the menstrual issues with my doctor, because I haven’t experienced any dizziness or lightheadedness from the blood loss, and I’m taking extra iron to combat anemia. The benefits definitely outweigh the inconveniences of menstrual irregularity, because I am already 50 pounds down, and I’ve got 150 more to go. I have 3-4 more months of my Phentermine to go, and I’m not giving up now!

  3. I was supposed to get my period and I started taking phentermine and I had cramps kept thinking it was coming and nothing . I still have not gotten my period and it seems that is a common thing with this pill.

    1. My period is 2 days late for no reason and I’m freaking out. I’ve been taking the phentermine a little over a month now and I’ve had some financial stress recently but that has eased slighlty as I started a new job and am back working but playing catch up and now this missed period is freaking me out.

  4. Currently, experiencing heavy flow with the phentermine! I have heavy clots and not sure should I take an iron supplement just in case. I am a little concerned but, that is normal! I am used to not having much of a period so this is very different! Reminds me of when’s i was in Job Corps and my period was like a faucet that would not stop! I do like the Phentermine and that I am eating less! I will contact my doctor tomorrow and find out what she would like for me to do about the heavy flow. This is the first time happening in a long time! Any insight?

  5. Since I’ve been on Adipex, my periods have came early. Each time on cycle day 25, and they have been shorter and lighter. It makes me think it’s skipping ovulation.

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