Phentermine is a popular and effective weight loss medication, but unfortunately, many users report that phentermine stops working after 2-3 months of use.
This decreased effectiveness is common because of the body’s natural response to weight loss and increased phentermine tolerance.
Over time, the body adapts to phentermine and its effectiveness can decrease. Phentermine tolerance is an especially common problem for patients who have taken phentermine for a long time or are taking it for the second or third time.
How long does phentermine tolerance last?
There are no official clinical studies of how long phentermine tolerance will last. Patient reports indicate it can last for months or years after stopping phentermine.
Is phentermine tolerance permanent?
No. A tolerance to phentermine is not permanent – it typically improves after taking an extended break from the medication.
Does a phentermine tolerance resolve after a break?
Tolerance often improves but does not resolve, after taking an extended break from phentermine.
What if phentermine is not working the first week of treatment?
It is surprisingly common to read user reports that phentermine did not “kick in” for 2-3 days. Even people that do not feel much effect at first usually begin to appreciate the pill’s effects within a couple of weeks.
What is a phentermine plateau?
A plateau is a temporary stall in weight loss.
Most patients experience at least one phentermine plateau, often 1-2 months into treatment.
There are three common explanations for a phentermine plateau:
One reason weight loss slows (or stops) a couple of months into treatment is increased phentermine tolerance. Patients tend to lose slower as the pills’ effects weaken.
2. Water Weight
Another reason is glycogen and water weight. Glycogen is the body’s most easily-accessible energy source. It is burned first when ‘calories in’ is less than ‘calories out’. However, in addition to quick energy, burning glycogen also releases a lot of water. As a result, many dieters lose a lot of water weight in the first few weeks. When the body eventually switches to other sources of energy (e.g. stored fat), this rapid weight loss stops (
3. Energy Balance
Finally, not adjusting intake and activity can also precipitate a phentermine plateau. A smaller, lighter body needs less fuel to power its everyday activities. So, it is important to adjust intake and activity to accommodate these now-lower needs.
5 Ways to Make Phentermine Work Again
Phentermine is designed as a short-term weight loss medication, and a decrease in effectiveness is often part of treatment with this pill. Thankfully, lifestyle changes can make a significant difference.
1. Increase Everyday Energy
Phentermine is famous for the strong, immediate energy it provides patients, but sometimes this boost isn’t enough.
Get more everyday energy by choosing to:
- Exercise regularly
- Eat nourishing foods
- Stay hydrated
- Prioritize sleep
Read more: How to Get More Energy from Phentermine
2. Boost Metabolism Naturally
Exercise is critical for maintaining a healthy and speedy metabolism.
Some foods, drinks, and spices also have a beneficial effect on metabolism.
Read more: How to Boost Metabolism Naturally
3. Set SMART Goals
Research shows that people accomplish goals more frequently when the goals are “SMART” (
- Related (to an overall goal)
Transform your abstract objectives into concrete SMART goals to give your weight loss journey a boost.
Read more: Setting Weight Loss Goals for Success
4. Prioritize Rest & Relaxation
Many people underestimate the importance of sleep and stress management in a successful weight loss journey. However, it’s vitally important to prioritize rest and manage stress.
Aim for 7-9 hours of sleep per night to balance hormones, reduce risk of chronic disease and give your body the time it needs to repair
Read more: Sleep and Weight Loss with Phentermine
5. Take Supplements with Phentermine
In an effort to make phentermine work better, many patients look for supplements to take with phentermine.
ALWAYS check with your prescribing doctor and pharmacist before taking any medication or supplement with phentermine – even if the product is “all natural”.
Some of the most common supplements to take with phentermine include:
- Capsicum/Cayenne Pepper
- Pre-Workout Supplements
- Vitamin B12
- Conjugated Linoleic Acid (CLA)
Read more: Best Supplements to Take with Phentermine
1. Mayo Clinic Staff. (2018, February 06). Weight loss stalled? Move past the plateau.
2. Centers for Disease Control and Prevention. (2018, February 13). Healthy Weight.
3. American Heart Association. (2015). Answers by Heart Fact Sheets: Lifestyle and Risk Reduction.
4. Kinucan, P., & Kravitz, L. (n.d.). Controversies in Metabolism.
5. Shaw, R. L., Pattison, H. M., Holland, C., & Cooke, R. (2015). Be SMART: Examining the experience of implementing the NHS Health Check in UK primary care. BMC Family Practice, 16(1), 1. doi:10.1186/s12875-014-0212-7
6. National Sleep Foundation. (2014, November 13). How to Fall Asleep Fast.
7. Pratt, K. (2014, January 8). UK researcher finds stress management may contribute to weight loss.