Phentermine and Glaucoma: Affects open & narrow angle glaucoma?

January 9, 2024 |

Posted By

Max Health Living is a reader-supported site. Purchases made through links may earn a commission. Learn more.

When trying to lose weight, it’s essential to ensure you’re doing it safely. After all, if you end up hurting yourself, it will not help your weight.

So let’s talk about Phentermine and Glaucoma. Phentermine is an appetite suppressant prescribed by doctors for short-term use in people who are overweight or obese. Like many other drugs, Phentermine can have side effects. There is a growing concern that one of its side effects is glaucoma.

Although there is no direct link between Phentermine and Glaucoma, studies show that Phentermine causes blood pressure and heart rate changes. High blood pressure may increase the risk of eye damage. 

People with glaucoma should be aware that Phentermine can make their condition worse. Especially if they already have low blood pressure or take other drugs that increase their risk of developing glaucoma.

Let’s find out more about how Phentermine links glaucoma and other general eye defects.

Does Phentermine Cause Glaucoma?

Glaucoma eye test

Phentermine can cause side effects related to your eyes that may worsen glaucoma. These include dimming vision and increased pressure within the eyes. 

If you have open-angle glaucoma and take Phentermine, check your eyes regularly. Your doctor can tell if Phentermine affects your condition at a routine eye check.

Although Phentermine may make open-angle glaucoma worse, it can cause or contribute to an acute attack of narrow-angle glaucoma. This Glaucoma type happens when the iris blocks drainage from the eye and causes a quick rise in intraocular pressure. 

Phentermine causes pupil dilation, which decreases iris mobility. The effect is a sudden rise in intraocular pressure. Therefore, it is not safe to take Phentermine if you have narrow-angle glaucoma. 

How Does Phentermine Affect Glaucoma?

A person taking Phentermine may experience dry eyes, blurred vision, and difficulty seeing at night.

Generally, Phentermine affects the eyes in two significant ways:

  • Increased risk of glaucoma
  • Worsening of existing glaucoma symptoms

Most of the adverse effects of Phentermine on Glaucoma and your eyes are due to the drug’s stimulant action. The side effects worsen symptoms of glaucoma.

Here are ways Phentermine may affect glaucoma:

1. CNS Stimulation

Phentermine is a central nervous system stimulant that raises heart rate and blood pressure.

Since Phentermine stimulates the central nervous system, it can temporarily increase eye pressure in some people who take it. The increase in pressure may worsen glaucoma symptoms or affect people with preexisting glaucoma.

2. High Blood Pressure

High blood pressure caused by Phentermine increases the force of blood against the walls of blood vessels, including those inside the eyes. This increased pressure can damage tiny blood vessels within the retina, leading to bleeding or hemorrhage into the retina (retinal hemorrhage).

Increased pressure may also cause fluid to leak from retinal capillaries into other parts of the eye (vitreous hemorrhage).

3. Sweating

Phentermine also increases sweating, leading to excess buildup of fluids around the eye and possibly causing glaucoma.

This condition occurs when excessive fluid builds up in the front chamber of your eye, causing increased pressure. The fluid pressure can damage your optic nerve, resulting in vision loss or blindness if left untreated.

4. Fluid Buildup

Excessive fluid buildup can also irritate the cornea, the clear tissue covering your iris (the colored part of your eye). Your corneas should be checked regularly for signs of glaucoma because this condition often has no symptoms until it’s advanced and irreversible damage has occurred.

5. Increase Light sensitivity

In addition to creating increased eye pressure, Phentermine can make you more sensitive to light and cause blurred vision or tearing of your eyes. These are symptoms related to glaucoma, but they do not indicate that you have developed it.

6. Pupil dilation

Phentermine causes pupil dilation. The effect makes it harder for you to see when driving at night or in dim light conditions. Wear sunglasses or protective eyewear at all times during the day when taking this drug.

7. Headaches

Glaucoma causes headaches, but using Phentermine can increase the headaches by increasing blood flow and pressure in your head and neck. Your headache is even worse than it usually would be while using this medication alone or with other drugs like caffeine or alcohol.

8. Vision changes

Phentermine can cause vision changes in people with normal eyesight and maybe even more dramatic for people with glaucoma. People suffering from Glaucoma might lose peripheral vision or get tunnel vision.

They can also have trouble focusing their vision on near objects or reading small print.

9. Increased intraocular pressure

Intraocular pressure (IOP) is the pressure within the eye itself. It is what keeps our eyes from collapsing under their weight. Increased IOP can damage structures within our eyes, leading to permanent vision loss. 

Phentermine and Open-Angle Glaucoma

Glaucoma comes in two forms: open-angle and closed-angle. 

Open-angle glaucoma is the most common type of glaucoma. It causes a gradual increase in intraocular pressure (IOP), eventually damaging the optic nerve and decreasing peripheral vision.

Phentermine can worsen symptoms for people with open-angle glaucoma because it increases blood pressure and heart rate, which both cause IOP to go up.

If you have open-angle glaucoma, you should avoid Phentermine. It can cause side effects like headaches, insomnia, irritability, and anxiety. These side effects may be more severe if combined with increased IOP due to phentermine usage.

There are two types of POAG: primary and secondary. 

  • primary open-angle glaucoma
  • secondary open-angle glaucoma

Phentermine and Primary open-angle Glaucoma (POAG)

Primary Open Angle Glaucoma (POAG) is the most common glaucoma, affecting more females than males. In POAG, the drainage angle between your iris (the colored part of your eye) and cornea narrows over time, causing too much pressure inside your eye.

The pressure forces fluid out of your eye space and into your bloodstream. It further damages the optic nerve cells that connect your retina to your brain, leading to vision loss and blindness over time. 

The exact effect of Phentermine on Primary open-angle Glaucoma is unknown at this time because studies are still ongoing.

However, Phentermine can raise blood pressure by increasing heart rate and constricting blood vessels. Increased pressure inside the eye can result in optic neuropathy or vision loss.

Phentermine and secondary open-angle Glaucoma (SOAG)

In contrast to primary open-angle glaucoma, secondary open-angle glaucoma occurs due to another eye problem.

Secondary open-angle glaucoma is caused mainly by intraocular pressure (IOP). This condition can cause other secondary effects, including macular degeneration, retinal detachment, and visual impairment.

If you have SOAG and take Phentermine, talk with your doctor about alternative weight loss methods that aren’t associated with this risk factor.

Phentermine and Narrow-Angle Glaucoma?

Taking Phentermine for weight loss increases your risk of developing narrow-angle glaucoma. 

Narrow-angle glaucoma is a type of glaucoma that occurs when the drainage angle inside the eye becomes wholly or partially blocked.

Phentermine, like other amphetamines, can cause dilation of the pupils (sometimes called mydriasis). You may also experience an acute attack of angle-closure glaucoma as your pupil dilates and causes more pressure inside your eye.

Optic fluid builds up in front of the iris, and the pressure can cause damage to the optic nerve. The effect may lead to permanent vision loss if not treated immediately.

Can you Take Phentermine if you Have Glaucoma?

Phentermine use is associated with an increased risk of glaucoma. Always consult your doctor if you think Phentermine may affect your health. 

Many people experience glaucoma symptoms when taking Phentermine. Take these precautions to reduce the risk.

The following tips can help you do just that: 

  • Avoid taking it for more than three months at a time
  • Use the lowest dose possible. It will reduce the side effects and make it easier for your body to adjust to the medication.
  • Get regular eye exams and see an optometrist if there are any changes in your vision or eye health.
  • Don’t use Phentermine if you’re an expectant mother or breastfeeding.
  • Don’t combine the drug with other stimulants like caffeine or amphetamines.
  • Don’t mix it with alcohol, especially if you have high blood pressure or cardiovascular disease.
  • Always follow the directions on the bottle when using Phentermine
  • Use caution when driving or operating machinery after taking Phentermine, as it may make you drowsy or dizzy
  • Choose a doctor who has experience with Phentermine and Glaucoma 

Phentermine comes with the risk of causing severe side effects. If you want to lose weight, other diet pills are out there that can help you achieve your goal safely and more effectively.

What is a Safe Diet Pill for People With Glaucoma?

 Phentermine is a drug used to help weight loss, but it’s not a good idea for people with glaucoma. 

Phentermine can increase blood pressure and cause fluid to build up in your eye. It makes glaucoma symptoms worse and leads to vision loss.

The good news is there are safe diet pills that don’t have these same side effects.

PhenQ is an all-natural, prescription-free supplement that helps you lose weight without increasing blood pressure or causing any other health problems. It boosts your metabolism and suppresses your appetite, so you feel fuller longer and don’t crave junk food as much.

What makes PhenQ even better than other supplements is its ingredients:

They’re all-natural. That means they won’t cause any adverse reactions in people with glaucoma or other health conditions, which means anyone can take them safely.

Another perk is that you don’t need a prescription to buy PhenQ legally. 


Should I Take Phentermine if I Have Glaucoma?

Glaucoma is a progressive disease that leads to blindness if left untreated. People who suffer from glaucoma should avoid Phentermine to lose weight.

Phentermine works by stimulating an increase in blood pressure and heart rate. This increase can put additional stress on your eye fluid and worsen glaucoma.

If you have glaucoma, talk to your doctor about your options for losing weight without using Phentermine or other stimulants.

Can Phentermine Raise Eye Pressure?

Like many other medications, Phentermine has side effects that can raise eye pressure. 

Phentermine may cause eye problems if you take it regularly.

In addition to intraocular fluid buildup, which can lead to damage or blindness, high eye pressure also increases your risk of developing glaucoma with time.

According to the National Eye Institute, people with glaucoma should not take Phentermine or any other drug or supplement that may raise eye pressure. Before starting treatment with Phentermine for weight loss, it is important to tell your doctor about all medications you are taking, including over-the-counter drugs and supplements.

Can Phentermine Cause Dry Eyes?

There have been reports that Phentermine’s ocular effects may be annoying (dry eyes).

Phentermine causes dry eyes by affecting the tear glands in your eyelids that produce tears. The eye tears keep your eyes moist and comfortable, so they don’t become irritated or feel like they are burning or itching. 

Dry eyes while taking Phentermine could lead to problems with your vision, like blurred vision or light sensitivity. The prolonged effect could result in discomfort when reading or using the computer for long periods.

The dryness of the eyes usually lasts for only a short time. If the symptoms persist,  discontinue the medication and see a doctor for an alternative drug for obesity.

Does phentermine mess with your vision?

One of the most common side effects of Phentermine is blurred vision or seeing double with one eye (diplopia).

It can affect both eyes or just one eye at a time. Diplopia from Phentermine usually goes away within a few weeks of stopping the medication.

It’s not known precisely why this happens, but it’s thought that the drug affects the part of your brain that controls eye movement (the cerebellum). The cerebellum is also involved in balance and coordination, so it may be possible that diplopia could affect these functions and vision.

What are the significant eye effects of Phentermine?

Some people who take Phentermine may have vision changes due to sudden pressure changes in their eyes caused by the drug’s breakdown and release into their bloodstreams.

This pressure change can affect blood flow through the optic nerve, which carries signals from your retina to your brain.

The result is decreased vision and possible permanent damage if not treated immediately.

Phentermine may also cause the following eye effects:

  • Accommodation problems:  Phentermine can reduce the ability to focus on near objects. Accommodation problems are common in people with certain eye conditions, such as cataracts or glaucoma. However, people who take Phentermine are at a higher risk.
  • Eye strain:  Strain on the eyes due to blurry vision or looking at something close up for a long time.
  • Eye pain:  Pain in one or both eyes that does not go away when you stop using Phentermine.

Phentermine may result in eye problems such as glaucoma and cataracts in severe cases. Glaucoma is an eye disease that can lead to blindness if untreated. Cataracts are a clouding of the lens in your eyes, making it difficult for you to see clearly.

Final Thoughts

Although more research is needed, phentermine users should be aware of the potential risk for glaucoma and take appropriate precautions.

Anyone with high blood pressure should consult their doctor to see if phentermine is a safe weight loss option, as it may increase the risk for eye damage.

Have you been prescribed phentermine?

Be sure to tell your doctor about any other health conditions you have and ask if there are any specific precautions you need to take while taking this medication. If you are in any way considering Phentermine – I’d advise you to check out PhenQ – a much safer replacement to Phentermine.

Important Disclaimer: The information contained on MAX HEALTH LIVING is intended for informational and educational purposes only. Any statements made on this website have not been evaluated by the FDA and any information or products discussed are not intended to diagnose, cure, treat, or prevent any disease or illness. Please consult a healthcare practitioner before making changes to your diet or taking supplements that may interfere with medications.

Who We Are

We are a team of fitness, health, and supplement experts, and content creators. Over the past 4 years, we have spent over 123,000 hours researching food supplements, meal shakes, weight loss, and healthy living. Our aim is to educate people about their effects, benefits, and how to achieve a maximum healthy lifestyle. Read more.