Phentermine And Coffee

Your Go-To Guide on Phentermine and Coffee

One of the most discussed topics in our Facebook Support Group (and Grupo Oficial de Apoyo) is phentermine and coffee, or phentermine and other caffeinated beverages.

Did your doctor talk to you about this combination when he or she first prescribed phentermine?

It’s a topic that often goes overlooked, but you should be informed about know how your medication interacts with this common pick-me-up.

Due to the weight loss pills’ stimulant properties, it’s not advisable to combine phentermine with caffeine.

So, here we’ll talk about phentermine and coffee, tea, soda & energy drinks, plus what you can drink instead!

How Much Caffeine Is In Phentermine 37.5?

Many people know that you shouldn’t combine phentermine and coffee, so it’s natural to wonder exactly how much caffeine is in phentermine 37.5. The answer? None!

Phentermine does NOT contain any caffeine. So why does this medication give you such a noticeable rush of energy? It comes from the medication’s active ingredient: phentermine hydrochloride (phentermine HCL).

Phentermine Energy

Phentermine HCL is a sympathomimetic substance with a chemical structure comparable to amphetamines.

It stimulates your central nervous system to give an “upper” effect similar to a “fight or flight” response.

This prolonged state of simulated stress is why you experience less hunger and more phentermine energy while taking the weight loss pills. It is, however, also why doctors encourage patients to limit or eliminate caffeine consumption.

Caffeine is a more mild but still effective stimulant. It is contained in drinks, food, and supplements and remains largely unregulated.

Like phentermine energy, caffeine energy is a product of central nervous system stimulation.

Since your brain is already receiving plenty of outside stimulation from the weight loss medication, drinking your normal morning coffee (or tea or soda or Red Bull) while taking phentermine can easily lead to an overload of external energy.

Phentermine and Coffee

Did you know that 54% of American adults drink coffee every day and that we drink an average of over 3 cups per day? Most of us (65%) have our cup of joe with breakfast, while a little under a third drink it as a snack between meals.

These statistics from the Harvard School of Public Health help explain why it’s so hard when your doctor tells you to give up coffee while taking a medication.

Due to the “upper” effect of both substances, and the potential for negative interactions, most doctors recommend skipping the daily caffeine jolt during your phentermine treatment.

As CNS stimulants, both phentermine and coffee (specifical caffeine) raise blood pressure, accelerate heart rate, and can produce insomnia.

Doctors recommend against combining these two substances because of the increased risk of serious side effects.

That being said, most phentermine patients report that they can tolerate a small amount of caffeine – equivalent to about one cup of coffee per day – without any noticeable reaction.

If you love your morning coffee and can’t fathom giving it up, speak to your doctor before combining phentermine and coffee (or any other caffeinated substance).

He or she can best assess the advisability of combining phentermine and coffee during your treatment and help you work out an individualized plan.

The same advice goes for combining specific brands of phentermine and coffee (e.g., Duromine and coffee, or Adipex and coffee).

phentermine and coffee and tea

Phentermine and Tea

Tea is a popular substitute for coffee, especially when you’re trying to cut down on caffeine.

Fruit and herbal teas – including popular flavors like mint, chamomile, cinnamon, and ginger – contain zero caffeine.

Rooibos tea doesn’t have any caffeine either. These drinks get their flavor from the simple infusion of plants in hot water, so they’re also calorie-free!

Given those promising qualities, fruit, herbal, and rooibos teas are great options if you’re craving a hot drink and hoping to avoid caffeine.

However, not all teas are caffeine-free. Black tea, green tea, white tea, and oolong tea all come from the Camellia Sinesis plant, and they all contain caffeine. More specifically, each cup of these teas has about 25-50mg of caffeine.

That’s still less than the typical 60-165mg contained in an 8oz cup of brewed coffee, but not at all insignificant. If you’re switching to tea to avoid phentermine and coffee, make sure you’re keeping your caffeine in check!

Phentermine and Soda

Not too worried about phentermine and coffee, but still clinging to your Diet Coke habit?

Unfortunately, soda has caffeine too. Eight ounces of cola contain 24-46mg of caffeine. Interestingly, classic Coke contains 34mg of caffeine while Diet Coke contains 46mg per can… and caffeine content varies country-to-country.

Clear sodas and root beer, however, are naturally caffeine-free. If you’re unsure about the caffeine in your favorite drink, check out the individual can/bottle and see for yourself!

That being said, if you’re cutting caffeine due to all the extra phentermine energy, it may be better to stick with completely caffeine-free options.

They now make caffeine-free colas and Dr. Pepper, so you don’t have to give up your dark-colored sodas if you’re not a fan of clear sodas or root beer. Better still, use your time on phentermine to build some healthy habits! Try to switch slowly from soda to water or unsweetened tea.

Phentermine and Energy Drinks

Energy drinks are something you should avoid entirely while taking phentermine. These super-charged drinks are the last thing you need when your body is already in overdrive due to phentermine energy.

The amount of caffeine contained in energy drinks varies from brand to brand, but most 16oz servings contain 160mg of caffeine.

This includes popular brands like Monster, Red Bull (80mg in 8oz), NOS, Rockstar, and AMP. Across the industry, caffeine content ranges from 50mg (Bai Antioxidant Infusion) to 357mg (Bang Energy) per serving.

At these levels, energy drinks contain more caffeine per can than most cups of coffee and should not be consumed while taking phentermine.

Even more, most energy drinks are super high in sugar.

For example, classic Rockstar contains 62g of sugar per can (16oz) while Red Bull has 27g of sweet stuff per serving (8.3oz).

Just like soda, they make sugar-free versions of these drinks, but most experts agree that water or unsweetened tea are much healthier options.

What Can You Drink While Taking Phentermine?

We’ve talked a lot about what you can’t drink while hyped up with phentermine energy, but what can you drink while taking phentermine? Here are a few easy suggestions:

  • Water
  • Herbal/fruit/rooibos tea
  • Decaffeinated coffee and tea (in moderation)
  • Infusions (infused water – hot or cold)
  • Skim milk, or unsweetened plant milk
  • Sugar-free lemonade or juice drinks (e.g. Crystal Light)
  • Sugar-free or ”no sugar added” hot chocolate (in moderation)

To learn a little more about why each option is preferable over phentermine and coffee and how to prepare them, keep reading!


Water is the most convenient, cheapest, and most nutritious beverage to drink while taking phentermine and in general!

Naturally calorie-free and hydrating, quenching your thirst with water is a healthy habit that helps you lose weight and maintain weight loss. It’s also free and widely available, so there is no excuse not to drink water.

Aim for at least 8 glasses of water (or another calories-free, caffeine-free beverage) per day to stay hydrated on phentermine.

Herbal, Fruit & Rooibos Tea

As we mentioned above, there are several varieties of tea that are naturally caffeine-free.

Some flavors of tea that contain zero caffeine include apple cinnamon, chamomile, cinnamon, cranberry, ginger, lemon/lemon ginger, lemongrass, mint, orange, peach, rooibos (aka redbush tea), and vanilla.

Most tea boxes are also marked with caffeine content, so you can double-check before you purchase your new flavor of tea!

Most major coffee chains (including Starbucks) also offer caffeine-free herbal tea options if you’d rather grab your drink on the go.

For the healthiest drink, enjoy your tea straight – no added milk or sugar. If you choose to sweeten your tea, take care to do so in moderation.

Decaf Tea & Coffee

Tea and coffee companies also produce decaffeinated versions of their traditionally caffeinated beverages. These drinks still contain an average of 2-5mg of caffeine per cup, so they’re not caffeine-free, but they are much lower in caffeine.

If you love your daily cup of coffee or tea, switch to the decaffeinated version while taking phentermine. Still, limit yourself to 1-2 cups daily since even small amounts of caffeine can add up.

If you’re more likely to grab a coffee on the road, remember that commercial decaf coffee tends to be a little higher in caffeine.

For example, a tall (12oz) Decaf Pike’s Place Roast from Starbucks has a whole 20mg of caffeine – far from caffeine-free!

On the other hand, Dukin Donuts offers a small (10oz) Decaf Coffee with only 7mg of caffeine, as well as a small Decaf Latte with less than 5mg of caffeine.

So, if you’re really craving a latte, check out Dunkin’s decaf latte. Just be careful to order it with skim milk and go for unflavored/unsweetened to avoid the hundreds of extra calories in milk fat and sugary syrup.


Infusions are very similar to teas but often steep for longer and use a larger amount of the plant or herb. It’s common to come across infusions of ginger, lemon, berries, and various herbs.

If you want to keep a refreshing, flavored drink at home, try infusing a pitcher of water in your fridge! Fill the container with water, and then add flavorings to your liking.

Let it sit overnight and you’ll have some delicious, calorie-free water in the morning! Common cold infusions include strawberry (or citrus) mint, cucumber mint, and watermelon basil. Ginger lemon is a popular warm infusion.


Dairy sometimes gets a bad rap in the weight loss community, and it’s widely under-consumed by young adults – especially young women.

According to recent surveys, 99% of American adults do not consume the recommended 2.5-3 servings of dairy daily! Milk is a great source of hydration, calcium, vitamins A and D, and protein.

If you’re lactose intolerant or vegan, fortified plant milk (e.g. soy milk, almond milk, etc.) can replace this food group and help you get the essential nutrients.

So, having a couple of glasses of skim milk or plant milk each day proves a healthy, beneficial choice for both phentermine weight loss and overall health!

Sugar-Free Drinks

Sugar-free drinks can prove a promising substitute if you just don’t like the taste of plain water or tea. If you’re in the mood for something chilled, single-serving powder packets, make any bottle of water into a 5-calorie juice drink in just seconds.

Many dieters take a liking to these super low-calorie, flavorful drinks and revel in the wide variety of available flavors. While taking phentermine, make sure to stick to traditional Crystal Light (or similar).

Some powdered juice products – including Crystal Light Energy, Sunrise, and tea products – contain varying amounts of caffeine.

If you’d prefer a warmer drink, try sugar-free or “no sugar added” hot chocolate. These diet hot chocolates are much lower in calories and will make you feel spoiled without breaking your diet.

Hot chocolate does contain a very small amount of caffeine (about 5mg) due to chocolate’s natural caffeine content, so enjoy this chocolatey treat as a healthy sweet treat or special extravagance instead of your everyday beverage.

As you can see, even though coffee and phentermine don’t make the ideal combination, there are plenty of delicious drinks (both hot & cold) that you can enjoy while taking this medication!

Do you drink coffee while taking phentermine? If you gave it up during your treatment, what do you drink instead? Share with us in the comments section below!

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  1. I take phentermine 37.5 in the morning an hour after breakfast. I’ve been drinking crystal light in my water because it said in the articles that it was ok too.

    Is sugar free Powerade ok? I’ve been drinking a few of those but I cant find any information if its ok or not while on the medication.

    I’ve been avoiding teas because I feel like all the ones I like have Caffeine in them so I just avoid them all together.

    Sticking to just water is hard but I’m working my way towards it, just hope I’m not ruining my progress with the sugar free Powerade.

    1. Hi Amber,

      Sugar-free Powerade typically contains electrolytes and artificial sweeteners like sucralose or acesulfame potassium. These ingredients generally don’t interfere with phentermine. However, it’s essential to be mindful of your overall intake of artificial sweeteners and sodium, especially if you have any cardiovascular concerns.

      Drinking water is always the best option. If you have specific concerns or underlying health conditions, it’s always a good idea to consult your healthcare provider for personalized advice.


  2. I take 15 mg. of Phentermine in the morning. I have trouble sleeping and have been taking CBD at night. I have been taking CBD before I started Phentermine. Are there any interactions with taking both?

    1. Hi Sue,

      CBD, on the other hand, interacts with the body’s cytochrome P450 system, a critical enzyme system for drug metabolism. This means CBD can potentially alter the metabolism of many drugs, potentially leading to decreased efficacy of the medication or increased side effects.

      While Phentermine isn’t specifically listed among the drugs that CBD interacts with through the cytochrome P450 system, the broad impact of CBD on this enzyme system and Phentermine’s potent stimulant effects suggest that caution is warranted. The combined effects of both substances on blood pressure and heart rate could potentially lead to unwanted side effects, especially in sensitive individuals or those with underlying health conditions.

      Given the complexity of drug interactions and the individual variability in response, it’s crucial to consult with a healthcare provider before combining Phentermine with CBD. A healthcare provider can offer personalized advice based on your medical history, current medications, and the potential risks and benefits of using both substances together.


  3. I take phentermine 37.5 in the morning around 8 am . I go to the gym around 7pm , is it okay to take pre-workout prior to my workout routine while in phentermine ?

    1. Hi Jay,

      Since phentermine already boosts energy by promoting a biological response similar to ‘fight or flight,’ taking a pre-workout supplement is just taking more of the same (and not in a good way). This combination could cause or exacerbate dangerous side effects like rapid heart rate or spikes in blood pressure.

      You cannot predict how your body will react, and every pre-workout supplement is different, so taking phentermine and pre-workout together is not a good choice.

      Instead of risking the combination of phentermine and pre-workout, try these ideas to boost your energy before a big workout:

      Try AM Workouts
      Schedule your workout around the time you feel the biggest energy boost from phentermine. Many people feel this rush within the first couple of hours after taking the pill, so consider exercising in that time period first thing in the morning.

      Fuel for Success
      If you find yourself hitting a wall during workouts, ensure you’re properly nourished and hydrated beforehand. While taking phentermine, it is extra-important to stay on top of proper hydration and eat regularly to minimize unwanted side effects or crashes during workouts.


  4. I have drank a cup of coffee and often don’t finish it. But my question is should I be taking my phentermine before I drink my coffee? If I should be taking it before how long should I wait to drink my coffee. I doesn’t race my heart just get bad dry mouth and now occasionally acid reflux.

    1. Hi Diane,

      Doctors recommend against combining these two substances because of the increased risk of serious side effects. However, some phentermine users still have a small cup of coffee a day. We would suggest taking your phentermine pill first thing in the morning and then waiting at least an hour before having your coffee.


    1. Hi Dana,

      Due to the “upper” effect of both substances, and the potential for adverse interactions, most doctors recommend skipping the daily caffeine jolt during your phentermine treatment. However, some users have reduced their intake to one cup of coffee daily and enjoy it at least one hour after taking phentermine.


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