7 Phenazopyridine Side Effects You Should Know About

Phenazopyridine (AZO) is a medication available over the counter (OTC) or by prescription. It can help relieve urinary tract infection (UTI) symptoms, such as urinary urgency, pain, and discomfort. Notably, phenazopyridine doesn’t kill the bacteria causing your UTI. You’ll likely also need to take an antibiotic to help treat the infection fully.

Phenazopyridine works quickly to improve UTI symptoms. While generally well tolerated, it can cause some side effects. And it’s a good idea to know how to manage them should they happen to you.

Phenazopyridine side effects at a glance

Most phenazopyridine side effects are mild. And they typically improve while taking or shortly after stopping the medication. Most people take phenazopyridine as needed for a few days. So, side effects are generally limited to that short period of time.

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Common phenazopyridine side effects include:

• Changes to the color of your urine

• Headache

• Nausea or vomiting

• Diarrhea

• Rash or itching

Rare but serious phenazopyridine side effects include:

• Methemoglobinemia (a life-threatening condition of the red blood cells)

• Hemolytic anemia (when your body destroys red blood cells faster than it can make them)

• Liver or kidney damage

Serious side effects typically only happen if you take an excessive amount of this medication. Below, we’ll review seven notable phenazopyridine side effects. But remember that this list doesn’t include every possible side effect people may experience.

1. Change in urine color

Phenazopyridine is a type of dye. It can cause a reddish-orange change in urine color. This phenazopyridine side effect is harmless and should stop after you finish taking the medication.

A change in urine color can be concerning, especially since it may look similar to blood in the urine. But if your urine changes color after you start taking phenazopyridine, it’s likely from the medication.

Phenazopyridine can also stain underwear or other fabrics. You may want to wear darker-colored clothing or panty liners while taking it. Stained contact lenses are also possible.

2. Headache

Headaches are another common side effect of phenazopyridine. They’re typically mild and limited to the time you’re taking the medication.

Here are a few at-home remedies you can try for headache relief:

• Increase your water and fluid intake.

• Avoid alcohol since it can worsen headaches.

• Add more movement or exercise to your daily routine.

• Take steps to improve your sleep routine.

• Try relaxing activities, like deep breathing, to reduce stress.

If these tips don't help, you may be able to take an OTC pain reliever, such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol). Ask your healthcare provider or pharmacist about which option is best for you. These OTC pain relievers don’t interact with phenazopyridine, and they might also help with UTI pain.

3. Nausea or vomiting

Nausea or vomiting are also possible side effects of phenazopyridine. They should go away when you stop taking the medication. If nausea or vomiting is severe or persistent, let your healthcare provider know. This isn’t an expected side effect and could indicate a more serious kidney infection.

It’s recommended to take phenazopyridine with food or after a meal. Taking your doses with something to eat can help lessen nausea. Staying hydrated and eating smaller, more frequent meals are other ways to help calm your stomach.

4. Diarrhea

Diarrhea can also happen with phenazopyridine. It should be mild and resolved when you stop taking the medication. Severe diarrhea isn’t typical and should be evaluated by a healthcare provider.

Here are a few tips for at-home relief of diarrhea:

• Avoid fatty, fried, or high-fiber foods.

• Try eating a bland diet for a few days.

• Drink plenty of fluids to stay hydrated.

If these tips don't help, you may be able to try an OTC medication for diarrhea, such as loperamide (Imodium A-D). Talk to your provider or pharmacist if diarrhea doesn’t improve with these steps.

Good to know: Diarrhea is a common side effect of many antibiotics. So, what you’re experiencing could be coming from the antibiotic you’re taking to treat your UTI — not phenazopyridine.

5. Rash or itching

Rash or itching are also potential side effects of phenazopyridine. In some cases, rash or itching can be a symptom of an allergic reaction. If you notice these side effects, stop taking phenazopyridine and contact your healthcare provider.

Severe allergic reactions to phenazopyridine are very rare, but they’re a medical emergency. Call 911 if you experience symptoms of a severe allergic reaction, such as:

• Difficulty breathing

• Fast heartbeat

• Tightness of the throat

• Dizziness or lightheadedness

6. Methemoglobinemia

Methemoglobinemia is a rare but potentially life-threatening phenazopyridine side effect. This complication usually only happens if someone takes an excessive amount of phenazopyridine. Be sure to follow the recommended dosages on your prescription or OTC label.

In methemoglobinemia, your red blood cells can’t carry enough oxygen to the rest of your body. It can lead to anemia (low red blood cell count) or hypoxia (not enough oxygen in body cells).

Call 911 or go to the nearest emergency room if you believe you’re experiencing symptoms of methemoglobinemia, such as:

• Trouble breathing

• Blue tint to the lips or skin

• Pale skin

• Sudden fatigue or weakness

• Trouble focusing or staying alert

• Seizures

• Feeling like your heart is skipping beats

• Fainting

Methemoglobinemia is a medical emergency and requires immediate care.

7. Hemolytic anemia

Taking too much phenazopyridine can also cause a rare side effect called hemolytic anemia. This is when your body breaks down red blood cells faster than it can make new ones. People with a blood disorder called glucose-6-phosphate dehydrogenase (G6PD) deficiency have a higher risk of developing this serious phenazopyridine side effect.

Hemolytic anemia can range from mild to severe. Mild symptoms include dizziness and weakness. Severe symptoms include abnormal heart rhythms and a liver or spleen that’s larger than usual. In many cases, hemolytic anemia requires no treatment. But other times, people need to be treated with blood transfusions.

If you have G6PD deficiency, discuss with your healthcare provider whether phenazopyridine is OK for you to take. And be sure to follow the recommended dosages for this medication while taking it.

When should I contact my healthcare provider about phenazopyridine side effects?

Most phenazopyridine side effects are mild and can be managed at home. But if anything seems excessive or doesn’t go away after finishing the medication, contact your healthcare provider.

You shouldn’t take phenazopyridine for more than 2 days without your provider’s OK. Phenazopyridine is meant to help ease UTI symptoms until your antibiotic starts working. If you feel like you still need this medication after 2 days, you should speak with your provider. You may need a different antibiotic for your UTI.

As with all medications, an allergic reaction is possible when first starting phenazopyridine. As mentioned above, if you develop a rash or itching, it’s a good idea to contact your provider. Call 911 if you experience severe allergy symptoms, such as trouble breathing or swelling of the face or throat.

Taking too much phenazopyridine can be harmful and increase the risk of serious side effects. If you believe you or someone you know has taken too much phenazopyridine, contact a provider. You can also call Poison Control at 1-800-222-1222 for guidance. If anything seems severe or life-threatening, call 911 or go to the nearest emergency department.

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Written by:

Nicole E. Cieri-Hutcherson, PharmD, BCPS, NCMP

Nicole E. Cieri-Hutcherson, PharmD, BCPS, NCMP, has over a decade of experience as a pharmacist, professor, and researcher. She was a full-time clinical professor in the pharmacy practice department at D’Youville School of Pharmacy before subsequently joining the faculty of the pharmacy practice department at the University at Buffalo School of Pharmacy and Pharmaceutical Sciences.

Edited by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

Reviewed by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

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