Phentermine and Keto Diet: does it work with keto?

January 9, 2024 |

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This article will take an in-depth look into the efficacy of keto and phentermine for weight loss and whether you should use them together or not?

The ketogenic diet is a famous low-carb diet used for weight loss and certain diseases.

On a similar note, phentermine is an appetite suppressant, and people have reported huge weight loss by using it.

But do you get maximized results when you combine keto with appetite suppressants?

In this article, you will find an answer to this question and see if is it a safe method. We have also included the reviews of people who have used the keto diet while taking phentermine.

And finally, you’ll find some general dieting rules and recipes to lose weight safely and effectively with phentermine by the end of this read.

So, let’s start and see if phentermine and keto can go hand in hand or not.

What is Keto Diet?

Keto diet

The keto diet is a high-fat, low-carbohydrate diet that has been used for centuries to treat various medical conditions.

The Diet was originally developed for people with epilepsy who were not responding to other treatments. The theory behind the keto diet is that by reducing carbohydrates and increasing fats, the body will enter a state of ketosis, in which it will burn fat for energy rather than carbohydrates.

This process can lead to weight loss and improved mental clarity.

In recent years, the keto diet has become increasingly popular as a weight-loss tool.

While there is no scientific evidence to support the claims made by proponents of the diet, many people report success in losing weight and improving their health.

Phentermine and Keto: Is it a safe combination?

An extreme diet strategy like the ketogenic diet may result in faster weight loss, but it is not a safe option with phentermine because the combined intensity of their side effects is likely to cause more harm than good.

The Keto diet includes a lot of fats and a good amount of protein but only a few carbohydrates.

This diet aims to induce ketosis, a metabolic state in which your body uses ketones (from fats) as an energy source when deprived of carbohydrates.

Hence, it gradually starts burning the stored fats, and you see a fast weight loss.

When you practice a keto diet while taking phentermine, you see an even faster reduction in your weight and body mass.

However, it is not recommended to use the phentermine and keto diets simultaneously because their combined effects are not studied well, and extreme results are possible for two reasons.

Firstly, drastic weight loss is not a healthy practice, and secondly, many of the side effects of keto and phentermine are the same.

The ketogenic diet is a highly restrictive diet in which you limit your intake of fruits, legumes, and grains to reduce carbohydrate content.

But at the same time, your ingestion of dietary water, fiber, vitamins, and minerals is also reduced, and you may develop nutritional deficiencies leading to many health problems.

And these problems can get worse due to limited food consumption under the influence of phentermine.

Hence, the adversity is likely to be augmented when you combine these weight-loss strategies.

Side Effects of Keto diet and Phentermine

Following are some of their common adverse effects:

1. Heart problems

In the keto diet, your lipid intake is quite high, which may cause lipid imbalance and high cholesterol levels.

When cholesterol proportion is high, fatty masses can form in the blood.

These insoluble chunks get stuck in blood vessels leading to vessel blockage and blood pressure irregularities.

If such a blockage is formed in a coronary artery, it can lead to heart attack, angina, or arrhythmia because the blood supply to heart tissues is affected.

Similarly, phentermine usage is associated with blood pressure rise, ventricular arrhythmia, and valvular distension in the heart.

So, the risk of cardiovascular diseases increases many times when you opt for a keto-phentermine weight loss plan.

2. Thirst and dehydration

Thirst and dehydration is other common complaint of the ketogenic diet and phentermine.

The Keto diet induces diuretic effects as glycogen reserves (maintained by carb intake) are quickly consumed, and water stored in them is lost.

Another reason is that ketone digestive products require more water for excretion through urine, leading to dehydration and enhanced thirst.

Also, you have restricted the intake of fruits which are a major source of dietary water.

Similarly, dehydration, thirst, and dry mouth are frequently reported by phentermine users, and combining it with the keto diet may cause severe dehydration.

3. Sleeplessness

Insomnia is a common symptom of ketogenic flu. It is usually caused due to sudden drop in the carb content and electrolyte imbalance.

Likewise, sleeplessness is also induced by the stimulatory action of phentermine, causing the release of neurotransmitters and stress hormones.

Hence, you are likely to be sleep deprived when doing keto while using phentermine pills.

4. Lethargy

People who do keto dieting often feel tired and lazy as they have quit the sources of instant energy (i.e. carbs).

Instead, their body systems rely upon fatty molecules, and energy production from ketones is a relatively slow process. Ultimately, energy transfer to all body cells becomes slower, resulting in lethargy.

On the other side, when you use phentermine, your calorie intake is decreased due to appetite suppression by phentermine. In this case, too, you provide lesser instant energy to the body and may feel fatigued all day long.

Despite the risks mentioned above, some people have tried using phentermine in addition to keto dieting; here are some of their reviews;

Phentermine and keto success stories

Social media posts from phentermine-keto users demonstrated effective weight loss, but they also reported some troubles.

A user saw a positive increase in weight loss after a month of taking phentermine-containing pills with the keto meal plan.

However, he also reported that he faced difficulty in falling asleep.

Similarly, a lady said that she lost weight fast with phentermine and keto but later felt she should only use one of these methods.

Another Reddit user said that he lost 15 pounds with the keto-phentermine diet, but his energy levels dropped very low during the weight loss phase.

His exact words were:

I had been previously a gym-goer, but this program slowed me to the point that I could hardly manage to sit on the couch after work.

Hence, the phentermine-keto plan offers weight reduction, but the negative effects also come along.

Instead, you can get desired results with a limited amount of calories through a balanced meal plan.

To help you select the right food for weight loss, we have added some delicious low-calorie recipes in the section below.

Best diet while on phentermine

delicious foods

If you want to reduce your weight, you need to limit your calorie intake so that your body can use the fats it has deposited over time. This phenomenon is called calorie or energy deficit.

The deficit limit is different for everyone, and you can calculate it for yourself with the help of your doctor or various online resources.

Usually, it ranges from 1400 to 1600 calories every day.

Another thing you should keep in mind is to choose healthy food items because if you munch on unhealthy snacks or foods that are filled with bad calories, your health will be damaged.

To make meal planning simpler, we have listed below the dietary ingredients you must take in your diet meals because their efficacy for weight loss is proven by science.


Protein content in diet meals is necessary because it keeps you full for a long time, and its additional amounts are used in muscle growth instead of fat storage.

Moreover, you need high protein to ensure that you are not losing your lean muscles while dieting.

Another benefit of a protein diet is it increases fat oxidation after workouts.

So, you will burn more fats during exercise if you take high-protein meals.

Proteins come from meat, eggs, dairy, and nuts.


Dietary fibre is synergistic to phentermine; it helps you feel full sooner and reduces the number of calories you consume.

Besides that, it improves your gut microbiome, which ultimately leads to improved metabolic rate in the body, helping you lose stored mass faster.

Seeds, grains, fruits, and vegetables are good sources of dietary fibre.

Vitamins and minerals

Vitamins and minerals are micronutrients, i.e. the nutrients needed in smaller quantities but significantly affect different body systems.

Among these micronutrients, Vitamin B, D, iron, and magnesium influence body weight.

Studies have shown that magnesium and vitamin B12 boost metabolism, preventing excessive weight loss. It is also observed that calcium and Vitamin D supplementation decreased fat deposits in the belly area.

Similarly, treatment of iron deficiency in many people has led to a decrease in weight.

You can get these vitamins and minerals by consuming more fruits and leafy vegetables.

Related posts:

Best Meals to Try While Being on Phentermine

For effective weight management, the recommended practice is to take 5-6 smaller meals instead of 2-3 big ones to avoid large spikes and drops in blood glucose levels throughout the day.

Because whenever you take a heavy meal, only a few calories are used immediately, and the rest are stored in the body for future use.

In contrast, when you supply a small number of calories after every few hours, most of these are consumed for body processes.

Up next, we are sharing easy recipes incorporating the dietary ingredients we talked about in the section above.

Spiced scrambled Eggs

This recipe is an easy but colorful and tasteful variant of the basic scrambled eggs.

Furthermore, it is loaded with proteins, fibre, and minerals. This recipe serves two, and a single serving has about 236 calories.


  • 1 onion.
  • 1 red chilli, chopped.
  • 2 tablespoon oil or butter.
  • 4 eggs, beaten.
  • 3 tablespoon milk.
  • ½ tomato, diced.
  • Coriander leaves.


  • Sauté onion in the butter until it is translucent
  • Add beaten eggs and stir
  • Add spices and pepper slices and fry till cooked

Peanut butter, banana smoothie

This recipe comes with the benefits of good fats from peanut butter, protein from milk and fibre, and magnesium from bananas.

Plus, the energy-boosting supply of healthy carbs from bananas and honey makes this smoothie a wonderful whole breakfast. Its calorie count is about 335 kcal.


  • 2 bananas
  • 2 cup milk
  • 2 tablespoon honey
  • 2 cup ice cubes


  • Add all ingredients to a mixer jar and blend until a smooth consistency is achieved
  • Top your drink with a few almond flakes and enjoy your quick power-pack breakfast

Veggie meatballs with tomato courgette

These vegetable meatballs with spiralized courgettes are vegan and gluten-free and have only 258 calories per serving. The following recipe serves 2.


  • 2 tablespoon oil
  • 2 tablespoon garlic paste
  • 1 onion, finely chopped
  • 100 g canned beans
  • 2 tablespoon vinegar
  • 1 beaten egg
  • 1 teaspoon chilli powder
  • 1 teaspoon tomato puree
  • ½ tablespoon ground coriander
  • 40g cooked sweetcorn
  • 15g ground almonds
  • 2 tomatoes, chopped
  • 2 courgettes, cut with a spirilzer


  • Mix eggs, beans, sweetcorn, tomato puree, and spices in a bowl.
  • Heat the oil and fry the onion for 5 minutes. Add these fried onions to the above mixture.
  • Make small-sized balls and line them on a baking tray.
  • Bake these at 220C for 15 minutes.
  • Meanwhile, warm tomatoes, garlic, and courgette in 2-3 tablespoons of water and serve with veggie balls.

Chickpea, tomato & spinach curry

This curry is a vegan-friendly dinner for a family of 6. This is an easy low-calorie recipe that provides 204 kcal per serving.


  • 1 medium-sized onion, chopped
  • 1 tablespoon ginger paste
  • 1 tablespoon garlic paste
  • 6 tomatoes
  • 1 tsp ground cumin
  • 1 teaspoon turmeric
  • ½ tablespoon oil
  • 2 teaspoon ground coriander
  • A pinch of chilli flakes
  • ¼ cup red lentil
  • 1 tablespoon of sesame seeds
  • 6 tablespoon coconut cream
  • 1 tablespoon cashews
  • 1 head of broccoli, cut into small pieces
  • 400g of chickpeas
  • 100g spinach leaves
  • 1 lemon


  • Blend tomatoes, onions, ginger, and garlic paste into a food processor.
  • Heat oil in a pan.
  • Add spices and the blended puree. Let it fry for 2 minutes.
  • Add lentil and coconut cream. Cook until the lentil is tender.
  • Mix in spinach leaves, chickpeas, sesame, and cashew, squeeze the lemon over it, and give it a good stir.
  • Take it off the stove after 2 minutes, and your healthy dinner is ready.

Oats and seeds Energy bites

These no-bake energy bites are a yummy snack to take for brunch or supper.

You can easily carry them along and energize yourself while traveling or after a gym session without the fear of crossing your calorie limit because they are just 110 kcal per serving.


  • 1 cup dried oats
  • 2/3cup coconut flakes
  • ½ cup peanut butter
  • ½ cup flaxseeds
  • 2/3cup chocolate chips
  • 1/3cup honey
  • 1 tablespoon chia seeds
  • 1 teaspoon vanilla extract


  • Combine all these ingredients in a bowl and mix
  • Cover the pot and chill it in the fridge for about an hour
  • Scoop out small bites (this recipe will yield about 2 dozen bites) and let them set in the air for half an hour
  • Your energy bites are ready. Store them in an airtight container at room temperature

Does phentermine interfere with ketosis?

Yes, phentermine can interfere with ketosis.

When you’re in ketosis, your body is burning stored fat for energy instead of glucose. So if you’re taking phentermine, your body may not be able to burn as much fat for energy. As a result, you may not lose as much weight or you may find it harder to lose weight.

You may also have a harder time keeping the weight off once you stop taking phentermine.


Phentermine therapy and the ketogenic diet are both useful methods to reduce body weight.

However, due to their overlapping side effects and drastic weight loss in lesser time, it is recommended not to use them together.

To shed off fats and lose weight safely, you can create a calorie deficit through a healthy balanced diet.

To achieve this goal, add a balanced mix of proteins, fibre, vitamins, minerals, good fats, and some carbs into your meal plan but restrict the total amount of daily calories below your body’s requirement.

So, your body will have to metabolize stored fats.

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