Can you drink coffee while on Phentermine?

Published on February 6, 2019 and last updated for accuracy on August 17, 2022
coffee beans

Who loves to drink coffee? I am sure many people does!

If you cannot start your day until you have guzzled down a cup of good coffee, then we have some great news!

Aside from the needed shot of energy to keep you awake and moving, it turns out that coffee can also help you lose weight.

Yes, you read that right! It can speed up metabolism even at rest.

Actually, caffeine has always been a staple ingredient in many weight loss supplements. It is the darling of all the intermittent fasters who take coffee instead of meals for breakfast.

Having said that, it’s time to take a fresh look at one of the newest health controversies – can you drink coffee while drinking other fat burning drugs like Phentermine?

Let’s find out by discussing in full details the many health effects of coffee and its possible interaction with Phentermine.

What is Caffeine?

Caffeine is a xanthine alkaloid compound that can stimulate the central nervous system. It temporarily boosts alertness. It is the most widely consumed legal psychoactive agent in the world (1).

It can be found in beans, leaves, or fruits of more than 60 plants like cocoa, kola nuts, guarana berries, and more (1).

Caffeine is commonly used to support mental alertness and help ward off fatigue. However, there are several other potential applications too.

Caffeine can be seen in weight loss supplements, energy drinks, and combined with analgesics to treat a headache (1).

How can coffee help in weight loss?

1. It mobilizes fat from fat tissues

Caffeine is a stimulant that can help break down fat (2). It does this by increasing the blood levels of epinephrine (3, 4). Epinephrine, also known as adrenaline, travels to fat tissues, signaling them to break down fats and release them into the circulation.

2. It increases your metabolic rate

The rate at which your body burns calories while at rest is known as the resting metabolic rate (RMR).

The higher your metabolic rate, the faster it is for you to lose weight.
Studies revealed that caffeine can increase RMR by 3-11% (5, 6).

However, the effect seems to be less pronounced among obese people.
Caffeine only increased fat burning by 10% in obese people as compared to 29% among lean individuals (7).

The effect is also greater in younger individuals (8).

3. It can curb appetite

One study proved that caffeine has an appetite-reducing effect in men. It makes them eat less after caffeine consumption (9).

Though these three mechanisms are promising, there is one major caveat – users become tolerant to the effects of caffeine through time.

Whether coffee can help you lose weight in the long term may depend on the individual’s lifestyle. At this point, there is no concrete evidence of such long-term effects; hence, people are still resorting to the use of weight loss drugs like Phentermine.

As we have mentioned earlier, most weight loss supplements contain caffeine. Is Phentermine one of them?

Actually, no. Phentermine does not contain any caffeine. The noticeable rush of energy in Phentermine comes from its active ingredient – phentermine hydrochloride (10).

What is Phentermine?

Phentermine is a sympathomimetic drug containing a chemical structure similar to amphetamines. It works by stimulating the nervous system to give a “fight or flight” response. This state of simulated stress makes you less hungry and energized while on Phentermine cycle (10).

It works well as an adjunct to exercise, diet, and lifestyle change.

Withdrawal reactions may occur it if has been used regularly in high doses or for a longer period of time. It should also not be taken with other diet drugs to avoid side effects.

This brings us to the question, can you combine coffee and Phentermine?
Drinking coffee while on Phentermine is said to be beneficial, but only in a moderate amount.

Benefits of drinking coffee with Phentermine

  1. Taking coffee while on Phentermine can further boost one’s metabolism.
  2. Energy level and stamina increase if you combine coffee and Phentermine. It can help improve your workout routines.
  3. The combination of coffee and Phentermine can help reduce the risk of type 2 diabetes and obesity (11).
  4. You can expect faster weight loss results

Side effects of drinking coffee with Phentermine

As mentioned earlier, you can only reap good benefits if coffee is used in moderation. When you abuse it while on a Phentermine cycle, there can be some adverse effects:

  1. One common side effect of Phentermine is insomnia (12). Combining Phentermine with high levels of caffeine can further increase the risks of insomnia and over-excitement.
  2. Phentermine and coffee are both stimulants. Too much caffeine can also increase your blood pressure and heart rate. Caffeine also stimulates the adrenal glands, increasing the production of cortisol and adrenaline. These hormones control the metabolism of carbohydrates and also affect your blood pressure (13).
  3. Gastrointestinal problems are common with excessive caffeine consumption (14).
  4. High levels of adrenaline in the blood can also cause emotional instability, anxiety, self-doubt, and more (13).
  5. Too much coffee with Phentermine doses can cause nausea, vomiting, and frequent defecation (11).

We know that it is so hard to give up coffee while taking medication because we drink it almost every day.

But due to the “upper” effect of both substances, and the risks of negative interactions, most doctors would tell you to skip the daily caffeine intake while you are on a Phentermine cycle.

If you really love your morning coffee and cannot fathom giving it up, can you go for a safer substitute?

Decaf Tea and Coffee

I am sure you have heard of decaffeinated versions of your traditionally caffeinated drink? These still contain an average of 2-5 mg of caffeine per serving but are much lower than what you usually take.

Most Phentermine patients report that did not notice any reaction by taking a small amount of caffeine, approximately one cup of coffee per day (10).

Try going for other healthier drinks too like herbal or fruit teas, infusions, unsweetened milk, or sugar-free lemonade.

Again, you should be careful when drinking coffee while on Phentermine to avoid negative side effects. Moderation is the key. It is also best to go to your doctor to discuss an individualized plan.