Phentermine and Birth Control: works together? (spotting, patch, shots)

January 8, 2024 |

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If you want to take phentermine for weight loss, it makes sense to ask whether it can interact with your birth control.

After all, some studies show that birth control pills can cause weight gain or increase a woman’s risk of obesity.

Will phentermine and birth control pills react with each other to produce harmful side effects or cancel each other’s effects?

Studies about phentermine and birth control interaction are limited, but using these two together can lead to breakthrough bleeding or spotting. However, despite the minor bleeding, phentermine use isn’t expected to decrease the effectiveness of your birth control or lead to pregnancy. You might still use the two together, but make sure to ask your doctor to be sure.

The same applies to phentermine and topiramate birth control interaction. Because a combination product like Qsymia also contains phentermine, it’s best to exercise caution and ask your doctor before using it with birth control.

However, it’s important to note that studies about phentermine weight loss and birth control are inconclusive.

So, it’s a good idea to learn more about their interactions before you decide on using them together.

Let’s dive in more.

Does Phentermine Decrease Birth Control Pills Effectiveness?

Birth control pills work by providing your body with a dose of estrogen that tricks that body into thinking you’re pregnant.

Because you’re “pregnant,” your body doesn’t produce and release an egg from your ovaries.

The birth control pills are supposed to be taken in regular intervals for this dose of estrogen to work throughout your monthly cycle. Once you complete the pills for that cycle, your body has lower estrogen levels, so you begin to bleed and have your period.

Phentermine appears to slightly disrupt this by making your body process the estrogen from pills more quickly. This can lead to early bleeding or spotting.

Although it is believed that phentermine doesn’t reduce the effectiveness of birth control, the regular hormonal fluctuations due to the quick estrogen processing might actually decrease the pills’ effectiveness and lead to possible pregnancy.

Phentermine And Birth Control Spotting

Phentermine isn’t likely to cause hemorrhage or uncontrolled bleeding. However, it can lead to spotting, which can be worrisome for some.

Tell your doctor about any changes in your bleeding patterns, especially if you’re spotting regularly or experiencing other adverse effects, including seizures.

Do You Need A Backup Birth Control Plan?

Because the actual effectiveness of your birth control pill can be affected by phentermine, it might be a good idea to have a backup plan.

Unless it’s alright for you to get pregnant, use a barrier method of contraception if you’re taking both phentermine and birth control pills.

How About Phentermine And Birth Control Patch?

Like the pill, a birth control patch also releases hormones such as estrogen. So, it can also be affected by phentermine.

Again, it might be best to use a barrier contraceptive method along with your birth control patch while taking phentermine, just to be sure.

Phentermine And Emergency Contraceptives

Ask your doctor’s help if you need emergency contraceptives because phentermine might reduce these drugs’ effectiveness. You might need a larger dose than what other women would normally need for these cases.

Discuss the dose of phentermine you’re using and the possible emergency contraceptive dose.

Your healthcare professional might need to confirm that you aren’t pregnant by doing a pregnancy before providing the emergency contraceptives.

If your healthcare professionals are aware of your phentermine and birth control use, they might be aware of this interaction and already monitor you for it.

IMPORTANT: Don’t start, stop, or change the dose of any medication (including your birth control pills) before checking with your healthcare provider.

Phentermine And Birth Control Effectiveness

Birth control doesn’t appear to have any effect on the effectiveness of phentermine, a stimulant that works by activating neurotransmitters in your brain.

So, you can still experience the effects of phentermine, including the adrenaline rush and appetite suppression, at around the same level even if you’re using birth control.

However, this isn’t 100% true.

Some studies show that hormones like estrogen can affect dopamine and other neurotransmitters in your brain. Because phentermine activates these neurotransmitters, then it’s also possible that its effectiveness can be affected by the hormones in birth control.

With so many conflicting results published in different studies, how do we really know which one to believe?

If you’re concerned about spotting or getting pregnant, then it might be good to ask your doctor if you need to stop phentermine use or try other weight-loss options.

Adipex And Birth Control Effectiveness

Adipex-P is a brand-name phentermine drug, so it can have the same interaction with birth control as generic phentermine or Qsymia (phentermine and topiramate combination).

So, can you take phentermine and birth control together?

Continue reading to find out.

Phentermine And Birth Control Weight Gain

Studies show that birth control use can increase your risk of obesity.

High levels of estrogen can cause fluid retention, which can lead to some form of weight gain. That’s the reason why birth control pills used to be associated with weight gain in the past.

Birth control pills from 50+ years ago (or from the early 1960s) contain very high levels of hormones estrogen and progestin.

Today’s pills have greatly improved but can still lead to some weight gain with fluid retention. You can get rid of this so-called “water weight” with exercise.

If you’re using phentermine, you can easily get rid of this extra weight because your body is more energized to exercise. Physical activity can burn extra fats and help you shed off this water weight in no time.

But even without phentermine use, you’re likely to shed off this weight gain in 2-3 months.

Better Alternative To Phentermine And Birth Control

Considering the possible negative interactions of phentermine and birth control, it might be a good idea to pick an alternative appetite suppressant such as PhenQ instead of pushing your luck.

With the risks and interactions we discussed above, you can make an informed choice about using an appetite suppressant with fewer side effects and interactions than phentermine.

PhenQ is a dietary supplement made with only natural ingredients that have no interactions with medications to the best of our knowledge.

If you’re serious about shedding off your extra weight while also making sure you don’t get pregnant, you can pick an appetite suppressant like PhenQ as part of your daily routine.

However, we recommend consulting your health professional to make sure your chosen birth control doesn’t interact negatively with any of this supplement’s ingredients.

Other benefits you can enjoy from using PhenQ:

  • Fights fatigue
  • Rebalances metabolic disorders
  • Anti-aging effects because it fights oxidative stress
  • Powers up cellular processes and improves ATP production
  • Burns fat, not muscles by reducing protein catabolism
  • Improves muscle mass
  • Controls lactic acid build-up during exercise so you won’t feel a burning sensation in your muscles that can stop you from trying harder
  • Increases your well-being
  • Improves muscle growth and repair


What Should You not mix with Phentermine?

Phentermine interacts with many drugs and medications. Be sure to check this list if you’re taking other drugs.

It’s also good to tell your doctor about any medication you’re taking so they can adjust the dose or prescribe other weight-loss options.

These drug components or medications can interact with phentermine:

  • CNS (central nervous system) depressants, including barbiturates, benzodiazepines, or sleep medications
  • Oral contraceptives (can cause spotting or irregular bleeding)
  • SSRIs (selective serotonin reuptake inhibitors), including Prozac (fluoxetine), Luvox (fluvoxamine), Zoloft (sertraline), and Paxil (paroxetine)
  • MAOIs (monoamine oxidase inhibitors), including Nardil (phenelzine) and Marplan (isocarboxazid)
  • Amantadine
  • Amphetamine
  • Antacids
  • Antihypertensives (such as beta-blockers)
  • Epinephrine (such as Epipen)
  • Linezolid
  • Procarbazine
  • Tranylcypromine
  • Selegiline
  • Rasagiline
  • Dopamine
  • Desmopressin

Did you know that phentermine can also react with natural supplements?

Don’t take the following if you’re using phentermine:

  • American ginseng
  • Eucalyptus
  • Guarana
  • Sage
  • Yerba mate

Can You Take Diet Pills While On Birth Control?

Some diet pills can interact with birth control. We recommend using PhenQ if you’re on birth control pills, but it’s best to consult your doctor to be sure that this combination is right for you.

What Can Interfere With Birth Control Pills?

Some medications and herbal supplements can interfere with birth control pills, making them less effective or causing various side effects.

Examples can include:

  • Antibiotics such as rifampin
  • Anticonvulsants or enzyme-inducing seizure medications for epilepsy, including Topiramate (Topamax), Carbamazepine (Carbatrol, Epitol, Equetro, Tegretol), Phenobarbital (Luminal), Phenytoin (Dilantin, Phenytek), Felbamate (Felbatol), Primidone (Mysoline), and Oxcarbazepine (Trileptal)
  • Some antiretroviral therapies (ART) for HIV, including Sustiva (efavirenz), Lopinavir/ritonavir (Kaletra), Nevirapine (Viramune), and Darunavir (Prezista)
  • Antifungal treatments such as griseofulvin (Gris-PEG), fluconazole, itraconazole, and ketoconazole (Extina, Nizoral, or Xolegel)
  • Diabetes medications such as Avandia (rosiglitazone maleate) and Actos (pioglitazone)
  • Pulmonary hypertension medication such as Tracleer (bosentan)
  • Herbal remedies like soy isoflavones, St. John’s wort, alfalfa, garlic pills, flaxseed, and saw palmetto
  • Anti-nausea medications such as Emend (aprepitant)
  • Stimulants for sleep disorders, including Modafinil (Provigil)
  • General anesthesia

What Does Phentermine Do To Your Hormones?

Phentermine triggers the release of hormones adrenaline and epinephrine, which are also neurotransmitters.

As for other hormones in the body, including sex hormones like estrogen, different studies have conflicting results. Some show that phentermine can make your body process estrogen more quickly, but others show no interaction between these drugs.

What Is The Strongest Weight Loss Prescription Pill?

Studies show that the phentermine-topiramate extended-release (Qsymia) drug is the strongest weight-loss prescription drug.

A 2016 study showed that this combination had the highest chance of helping users lose at least 5% of their body weight than the placebo (control) and other commonly prescribed weight-loss drugs.

This combination can also work better at higher doses. So, the higher the dose, the more weight loss you might experience.

However, because Qsymia contains phentermine, you might want to consider choosing PhenQ if you’re also using birth control pills.

Can You Take Phentermine Longer Than 3 Months?

Studies about long-term phentermine use also have conflicting results.

For example, a 2019 study showed that longer-term users (12+ months) of phentermine experienced more weight loss of around 7.4% than the control group. The study didn’t find a significant difference in the hazard ratios between short-term and long-term users.

However, doctors still caution against using this drug longer than 12 months because of its potential for abuse.

The FDA (United States Food and Drug Administration) and most doctors actually recommend a maximum phentermine use of 12 weeks.

If you’re serious about your weight-loss goals and wish to continue using an appetite suppressant, then PhenQ might be the right one for you. It’s not a controlled substance and can be used for as long as you want, without fear of possible abuse or serious side effects.

Final Thoughts

Phentermine and birth control are two commonly prescribed medications, but there is limited research on their interaction.

In general, phentermine use is not expected to decrease the effectiveness of your birth control or lead to pregnancy. However, if you are taking these medications together, it’s important to talk to your doctor about any potential risks.

There might be a better appetite suppressant like PhenQ that can help you lose weight without any side effects or complicated prescriptions.

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