Weaning off Phentermine: 6 things I wish I’d known

If you’re weaning off phentermine, there are a few things you ought to know. Oh, wait. You want to know why know how to wean off phentermine? Well, it’s because when I first started to lose weight, I didn’t do it all by sheer willpower, diet, and exercise. I used phentermine, and it was pretty awesome. But there are a few side effects that you should know about as you wean off.

After going on the low glycemic index diet for three months, I plateaued. I stood still at having lost 30 pounds. I wasn’t gaining weight back, but I wasn’t losing any extra, either.

And for someone still above 250, it was disheartening. I hadn’t lost any size in clothes–I was still wearing XXL or XXXL shirts and 42-44 waist pants. It was hard for people to tell I had lost any weight at all. And that really matters at that stage of weight loss.

So I went to the doctor and started a physician-monitored, medical weight loss program. I took vitamin injections once a week and went on a medium dose of phentermine (or you may have heard them called adipex diet pills before, too).

Phentermine, the generic version of adipex, is similar in composition to an amphetamine. It’s an upper that gives you tons of energy, a lack of appetite, and some pretty severe side effects. But for the time I was on adipex for weight loss, I loved it. Weight just melted off, I was so rarely hungry, and I had the energy of a 4 year old on sugar. It was a miracle drug for me, and it took a long, long time for me to even think about weaning off phentermine.

Breaking a weight loss plateau with Adipex

I started taking the diet pill in October 2010 (because I found out that my health insurance covered the regular doctor visits). Once I had that delicious phentermine pumping through my veins, I felt as powerful as Bane on venom. The pounds melted away. And I was barely exercising at all. Maybe two hours of light tennis with my wife a week. Within 12 months, I had dropped to 203 pounds (from 270-280ish) and weaned myself off the drug.

Yep, I had successfully weaned off adipex. In December. Two weeks before Christmas.


Suffice it to say that I gained some of the weight I had lost back. Which was okay. I expected that. Then my dad died in April, and I stress ate myself back up to 230-235ish.

That was not okay.

When I went to the doctor to see about using phentermine again, I was told my blood pressure was too high to risk taking the drug–170/85. I had to lower it before they would even consider it.

So I used some of the money I made from selling my first short story and bought a bike and started cycling around town instead of driving. Once I did that, I started walking places, too. And it only took a week or so of that to get back into using couch-to-5k apps to start running.

I had lost down to about 220 by the time I started running, and I went to the doctor, and my blood pressure was fine–120/60–so she put me back on phentermine, which I decided would be my last round. I would use the extra energy it gave me to build up a running and exercise regimen, get myself into shape, and then drop it for good by fall/winter.

Two full years from the time I popped my first pill, I was weaning off phentermine.

I had hit my goal. When I hit normal BMI (body-mass index), my doctor could no longer legally prescribe the drug to me–which is great because it was beginning to adversely affect me, anyway. My blood-pressure was rising again, and my moods were becoming erratic. Once I made the realization the drug was negatively impacting my life, I was finally able to start weaning off phentermine.

It didn’t take long to wean off phentermine completely, and I have been off the adipex diet pill for years with no adverse effects to my health.

I don’t regret using the drug; it really kickstarted my weight loss. However, I do wish I had done things a bit smarter along the way. My doctor did a good job of telling me about the clinical side of taking it, but it was unlike any other diet pill I had taken before (and I had tried a lot, being a fat guy my entire life). If you’re considering a medical weight loss program, these are a few of the most important tidbits I learned during my program, that weren’t necessarily my in my doctor’s wheelhouse.

  1. You must exercise. You must change your diet. You will lose weight on phentermine if you don’t, but the moment the drugs leave your system, you’ll gain all of it back. And then some. Which is terrible for your body. Phentermine is a crutch, not a solution. You must change your lifestyle and keep it changed. If you don’t, you’re wasting your time.
  2. Phentermine makes you thirsty all the time. ALL THE TIME. I would drink upwards of 100 ounces (yes, 100 ounces) every single day and still be thirsty. The first week, I didn’t realize just how much water was necessary and gave myself kidney stones.
  3. Your mood will fluctuate wildly. One minute, you’ll be as nice as can be. Then you’ll be raging about something truly insignificant. Just watch a few episodes of Breaking Bad, and you’ll see the kind of mood swings amphetamines can cause. Seriously.
  4. You will bounce off the walls for months. You’ll be jittery. You will have more energy than you know what to do with. Then, you won’t notice the energy at all. Do something with it while you can. Start running, get used to exercise, before you have to wean yourself off the drug and don’t have that crutch.
  5. Your blood pressure will rise (but it will go back down when you’re weaning off phentermine, so it’s not a permanent thing). Maybe it will rise a little, maybe a lot. But it will. Keep an eye on your BP, even between doctor visits, or you’ll hurt yourself. That’s why this is a medical weight loss program. (Note: do not buy adipex or phentermine online. It is incredibly dangerous, and you do so at your own risk. Please, please listen to me on this.)
  6. The more weight you lose, the more the drug will affect you–which is why “normal” BMI folks can’t get scripts for it. As I got smaller, I also got moodier, thirstier, and higher blood pressure. Not a good trade-off. Not at all.

The important thing, though, is that I changed my lifestyle. I’m a runner now, I eat hardly any meat, and only enough carbs to get me through my workouts. I do cardio, and I’m starting to take baby-steps into strength training.

The phentermine was just a crutch bridge that helped me to get from one point in my life to another. I used it It was a tool, the same as my running shoes are tools. Remember, phentermine doesn’t effect permanent change–you have to use the boost it gives to change your lifestyle, or you’ll negate the benefits you gain.

Remember that.


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  1. Che

    I tried caffeine pills and it was a horrible experience. I was working as a lifeguard at the time and got very dehydrated and jittery! Not good for being up on the stand!

    I know one of the big reasons that people see a plateau in weight loss after 20-30lbs when they ARE exercising is that they start gaining muscle! A lot of people miss that because they are focused on the scale, which is unfortunately.

    • B.J. Keeton

      I did that with the phentermine. I dehydrated myself so badly that I’m still overcompensating for it. My students even joke about how I can’t go anywhere without my blue water bottle.

      These days, I’m trying to deal more with tone and size than weight, and it’s very hard to transition into. I’ve been doing more strength stuff, but not a ton, and I am having a hard time finding reliable numbers on how long it takes (on average) to build a pound of muscle. Probably longer than I think. 😉

  2. Sarah

    I don’t know if anyone still monitors this website, but I am on Adipex now and I am NEVER thirsty! It is like my thirst is gone – the opposite of what the drug usually causes. What do you think is up? I’m worried. I’ve lost about 20lbs and I’m a month and a half in.

    • B.J. Keeton

      Oh, wow. I think that’s fantastic that you don’t feel the thirst from Adipex. I am actually jealous, haha.

      Honestly, if you’ve lost that much and your doctor isn’t concerned, it may be nothing. Medications affect folks so differently that you may not experience that side effect. If you haven’t told them that, I’d absolutely bring it up.

      My first thought, though, (and I am no medical professional) is that you are probably hydrating a lot better than I was ever able to.

      Also, congrats on the 20lbs! You’re a rock star!

      • MiyMiy

        Thank you so much for sharing your story I have been taking phentermine for about four years straight and it helps me to not feel bloated all the time I really want to ween myself self off of it but I’m scared of the side effects and scared of gaining the weight back to be honest at this point I haven’t really lost any weight now I am exercising full-time and I’m wondering if I should take it for another month with changing my eating habits and working out six days a week so I can lose the weight I want and then ween myself off your message has been such an inspiration if you have anymore tricks please let me know I need the help.

      • Catie

        I started phentermine 9 days ago and I was blown away with how it made me feel and so quickly. I felt like maybe it brought me rapidly out of a mild depression that i didn’t know I had. I had no idea how so many things in my life were impacted by low energy levels and fatigue. Things that I was bringing myself down for because I thought all this time I was doing them for other reasons. (Not sure if that makes sense). I felt so good that after 3 days of taking it I sat down and cried because I knew I was only on this for 12 weeks and I didn’t want to lose that feeling. I feel like I’m the person that I always wanted to be. The person that seems to have their crap together and have energy and they are organized and they get things done. I do get the thirsty feelings but I always have water with me so that doesn’t bother me much. I also have constipation but that had started prior because I started losing weight on keto so both of them together slowed everything way down. I am also barely eating so that slows stuff down too. My heart rate has jumped about 20 bpm and blood pressure went up around 10 points. I bought a heart rate monitor for the gym and personal training sessions. I hope this high energy lasts it really is life changing for me. I’ve read people sometimes get crazy high libidos and I hope to have that because I have had super low/non existent libido for years which I think is partially due to my weight gain. Anyways that’s my experience on it so far 🙂

        • AD Bomb

          I felt good at first as well. Then became more moody and anxious. I combined it with gabapentin for mood, but then I felt drained and tired.
          I actually have ADD and Adderall didn’t make me feel drained.
          Going to try AMPK to shrink my fat cells.
          It energizes your metabolism as well. Still feel too sluggish for running but I did start Pilates to help with toning. Best of luck to everyone.

          • Savannah

            To B.J., do you think maybe your thirst comes from keeping your body in a state of ketosis? That makes me thirsty because I hardly eat any carbs. I have been doing phentermine for almost 10 weeks now. I have lost 15 pounds. I need to lose about 10 more pounds. I exercise about an hour a day most everyday and eat little carbs. I feel confident I will be able to keep it off. What is something similar to phentermine that you all have found that works?

    • Michael P

      People will experience different t results. I lost probably 40-50 lbs in two months, if my memory serves me. I also intermittent fasted as well which worked wonders. The adipex curbed the appetite to allow the fasting. I was a little thirsty taking it, just drink water. I am starting back on it today after being of more than two years. If you go back to your old ways of course you will gain weight. Keep eating right, taking the med as prescribed, exercise and drink water. You will be fine!! My focus is really nice while on Adipex as well.

  3. Cricket

    Congratulations on your weight loss journey!!! I am a grandmother that has dealt with systemic Lupus and Fibromyalgia most of my adult life, pain almost all of the time, stiffness and swelling and an endless amount of medications with awful side effects that almost always included weight gain. Given that I have dealt with weight challenges my entire life and always been an overweight curvy/thick lady, I certainly didn’t need that kind of mess added to what I was already working with. January 20, 2014 I had to have a surgery and there were complications that left me with a serious spinal cord injury and mostly disabled on my entire left side. After weeks in the ICU and a lengthy recovery and slow process to regain mobility added to the meds that were adding to the weight problem, I am now officially obese with a BMI of 38 I believe. My pain management doctor just had me start Topamax with hope that it would help with some of the weight loss as she believes people with mobility and chronic pain issues may not do well on Adipex because the doses may be too strong and mask pain, you feel great and over do it and actually cause the pain to increase, but my argument is that my weight and diet are actually stable for >2 years, under 1500 calories a day and holding strong at 203 lbs (only 5′ tall). Now that I am finally off the meds that put the weight on, I would love to be able to try something to help take some of the weight off so I may be able to even increase mobility and reduce pain and keep weight I am able to lose stable on my own. My question is, were you able to regulate the dosing at all to help mitigate any of the side effects, did you use any kind of dosing schedule where you were on for some days and off for some or higher on some days than others etc? And a side note, many of my medications make it difficult to absorb vitamins and minerals from my diet, now that I reread your article, did you find that you needed to add any mineral supplements back into your diet with all of the water you were flushing through your system? Sorry such a long post, cheers!

  4. Caroline Preuss

    Klasse! Endlich mal jemand der weiß wovon er redet! Toller Beitrag, Dankeschön! 🙂

  5. Chris Hughes

    I am at a complete loss. I’ve taken phentermine in the past with success 8 mo ago but after 5 weeks it didn’t have the same effects. I restarted almost 3 weeks ago and it suppressed my appetite (and most importantly binge eating sweets) for maybe a week. No thirst or dry mouth now and ate a bag of cookies the other day – I’m at a loss. Two things have changed although they shouldn’t effect my body’s response to phentermine: I started 25mg of Zoloft and stopped taking hormone replacement med. What in the world?

  6. Kevo

    I’be been taking Phentermine for 3 months now & with working out & eating healthy I’ve lost 63lbs!! I’m loving the results of it but HATE the side effects.. if it wasn’t for the rapid weight loss, I would’ve stopped taking it a long time ago.. I’m not sure how it effects Women but Men must know one important thing before taking it.. Your sex life will suffer.. at least mine has.. I’ve never had any erection issues before until I began taking Phentermine.. I just pray it’s temporary.. I will finish this dosage I have but will be done with it after it’s gone.. I’m confident I can maintain without it now!

  7. Misty

    Do you know of any OTC meds that work as well as phentramine to curb your appetite. Or I have been also looking for a good low carb protein shake that actually helps in keeping you full.

    • ADBomb

      It is legal but usually you have to order it on EBay. Primatene will give you energy and less cravings.
      Also the supplement AMPK for reducing fat and speeding up metabolism. Try taking a few days off intermittently so your body builds less of a resistance. Increase your dose with plenty of rest and water.

  8. Michelle

    I started phentermine at 215 pounds in May 2019, it is now October 2019 and I am at 163 pounds. I did stop for 1 month at about July 2019. Total lbs lost is 52. I’m so happy I was able to get phentermine it’s the best thing that Happened to my body. Yes I experienced side effects. First week was INSOMNIA I’d be up til 4am and had to get ready for work by 6am. So I just started taking it earlier. The other side effect for me was being thirsty. Other than that not many other side effects , Blood pressure was always good. , I love the energy it gave me . Before phentermine I’d do a 30min walk , when I started phentermine I was able to go 1 hour or more up hill down hill etc… The one month I was off phentermine I did not gain back the weight , it would fluctuate up and down by 5 lbs but nothing else. I’m now on my last bottle and I’ve been just taking it ever 3 days or so. My doc will not prescribe more due since my BMI has lowered. I’ll continue to eat better and exercise. I’m confident that the weight will stay off. Good luck to you all ! I’ve had a great experience with phentermine.

  9. Ann McGinn

    I started Phentermine 8 months ago…………i have lost 35 lbs . i workout like 5 times a week and i feel so good . however i do need to stop taking it for awhile. I did try and i immediately felt so terrible, cranky and moody. anyone else? I just finished my month supply and I am going to try to not refill it. suggestions ? comments ?

  10. Ashley

    Thank you for posting this. I’ve been on it almost two months and just realized how bad the phen rage is. It’s to the point that it’s actually scary. Like I have no control over my anger or what I do while angry. I will be starting to wean off of this crap medicine tomorrow

  11. samantha

    hi, i’ve been on phentermine on and off for a year now. i started at 210 pounds and i’m now 155 and they still have me on it. i stopped taking it a few times because i was feeling overly aggressive, but lately i have been getting light headed and i’m not sure if its phentermine or stress. I want to stop taking it but i’m worried i will gain the weight back. i also currently do a modified Keto diet, i don’t really exercise much, i know i need to start but i’m always so exhausted so the energy part of phentermine i feel like doesn’t help much anymore. i also get really hungry when i skip my phentermine for the day so that sucks. any advice is welcome.

  12. Joli Mason

    I know you have probably stopped monitoring this post, but I just want to say thank you for sharing and leaving it up and available! I was on phentermine for 7 months and lost 30lbs. 220 down to 190. I quit smoking in February 2021 (before adipex) and my resting HR went from 85 down to 65. My BP was a consistent 119/80. When I started phentermine in April of 2021, my RESTING heart rate never went up, but my Active HR did, ranging from 75-110, but this was if I was up from my desk moving around (I’ve always walked fast) bending, lifting things (0-20lbs). And my Workout HR was easier to achieve which was awesome. Interestingly enough, my blood pressure while on phentermine decreased, from average 119/80 to an average of 112/75 . Weird right? Lol anyways, I just wanted to comment on this for folks to see different experiences. And to say that your story has helped me in the sense that you lost the weight, and did what you needed to, to keep it off. I plan on getting back on phentermine in January 2022 and anticipate already having a gym routine in place along with better food choices (im a carbs girl, not a sugar girl). I am still in the high risk BMI area at 31.52 (my height is 5’5 and age 37 ugh haha). Your success story gives me real Hope about being able to maintain the weight loss. Thanks so Much!!!

  13. Barb

    I’ve been on Phentermine for a year now and am starting to ween off of it, which is why I found this article. I had almost none of the symptoms you stated. Insomnia was a big one a couple months in. I cut my dose in half and that took care of that. At least half the time I’ve been taking a half dose and only every other day at that. So I’ve probably been taking less of it than you. My fear has been that once I stop, I will just go back to over eating again. I am now working on my relationship with food. I’m eating lots of healthy things and not worrying about weight gain. I’m following Lacey Baier on Youtube. I’ve reached my goal weight and feel great.


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