8 Foods You Shouldn’t Eat When Taking Sulfamethoxazole/Trimethoprim

Sulfamethoxazole, a form of sulfa, is combined with trimethoprim, a synthetic antibiotic, to form a widely prescribed antibiotic sold under the brand name Bactrim. 

It is used to treat bacterial infections such as middle ear, respiratory, urinary tract, and intestinal infections. 

However, it can interact with a wide range of drugs and foods.

If you or someone you know has recently been prescribed the antibiotic sulfamethoxazole/trimethoprim, it is important to understand which foods to avoid and which to consume while on the medicine. 

This is because certain meals can interfere with the absorption and efficiency of Bactrim, resulting in unpleasant side effects.

Foods To Avoid When Taking Sulfamethoxazole/Trimethoprim (Bactrim)

When using antibiotics such as sulfamethoxazole/trimethoprim, you should avoid certain foods as they may impact their absorption and effectiveness. 

1) Alcohol

Bactrim can prevent the liver from breaking down alcohol. This may result in a “disulfiram-like” interaction. 

Sulfamethoxazole/trimethoprim may interfere with acetaldehyde dehydrogenase, a chemical that aids in the breakdown of alcohol so that your body can metabolize it. 

This reaction is comparable to that generated by the drug disulfiram (Antabuse), which is used to prevent alcoholics from drinking.

Avoid all foods or beverages containing alcohol while taking Bactrim because they can cause symptoms such as severe nausea and vomiting, shortness of breath, facial flushing, irregular heartbeat, and headache.

Foods cooked with alcohol may retain an unexpected amount of alcohol, so avoid them when taking Bactrim. 

When you add alcohol to a sauce and remove it from the heat, 85 percent of the alcohol content is retained. 


2) Potassium-Rich Foods

Bactrim may raise potassium levels in people who have poor kidney function. If you have kidney problems, see your doctor about whether you should avoid potassium-rich salt replacements as well as potassium-rich foods such as:

  • Cooked spinach
  • Chocolate
  • Bananas
  • Milk
  • Pumpkin
  • Potatoes

3) Food Containing Propylene Glycol

When taking medications like sulfamethoxazole and trimethoprim through injection, it’s essential to avoid consuming foods or beverages that contain propylene glycol. 

Propylene glycol is a common chemical compound found in various processed foods, soft drinks, and even pharmaceutical products. 

This interaction is particularly important to be aware of due to the potential for dangerous consequences.

When combined with certain medications, propylene glycol can potentially affect the body’s metabolism and clearance of the medication, leading to adverse effects or decreased effectiveness. 

In the case of sulfamethoxazole and trimethoprim, the presence of propylene glycol could alter the way the medication is processed in the body.

As a result, it’s advised to abstain from consuming foods, beverages, and pharmaceutical products that contain propylene glycol while undergoing treatment with medications like sulfamethoxazole and trimethoprim through injection. 

4) Highly Acidic Foods

Highly acidic foods like citrus fruits, tomatoes, and sodas should be avoided while taking sulfamethoxazole and trimethoprim. 

These foods can significantly impact the absorption of antibiotics. The acidity in these items can alter the pH of your stomach and digestive tract, potentially affecting the effectiveness of the medication. 

By avoiding these acidic foods, you can help ensure that the antibiotics are properly absorbed and can work optimally in combating infections.

5) Calcium-Containing Foods

When on a sulfamethoxazole and trimethoprim regimen, excessive consumption of calcium-rich foods can hinder the absorption of the antibiotics. 

Opting for fermented dairy products instead of high-calcium options can be a workaround to ensure that the medication is effectively absorbed.

calcium rich foods

6) Fortified Foods

Similar to naturally calcium-rich foods, fortified foods with added calcium content can also interfere with the absorption of sulfamethoxazole and trimethoprim. 

The additional calcium content in fortified foods exacerbates the competition for absorption in the digestive tract. 

Steering clear of these fortified options is recommended to ensure that the antibiotics are fully absorbed and can exert their desired effects.

7) Grapefruit and Its Derivatives

Grapefruit and products derived from it, such as grapefruit juice, should be avoided while taking sulfamethoxazole and trimethoprim. 

Grapefruit contains compounds called furanocoumarins that can inhibit enzymes responsible for drug metabolism in the liver. 

This can lead to elevated levels of the antibiotics in your bloodstream, potentially causing adverse effects or altering the medication’s effectiveness. 

By avoiding grapefruit and its derivatives, you prevent unwanted interactions and ensure the antibiotics work as intended.

8) Caffeine

Caffeine is a stimulant that can have effects on blood pressure, restlessness, and sleep patterns. 

When combined with sulfamethoxazole and trimethoprim, which can also lead to anxiety or sleep disturbances as side effects, these effects might be amplified. 

While caffeine itself doesn’t directly interact with the medication, the combined impact on your body can exacerbate discomfort. 

Avoiding caffeine can help mitigate potential additive effects and allow your body to cope better with any medication-related symptoms.

Get Your FREE Sleep Guide

  • Learn how to naturally improve your sleep
  • Dietary recommendations, supplements, and lifestyle changes
  • Developed exclusively by our medical doctor

By clicking “Download Now”, I agree to Ben's Natural Health Terms and Conditions and Privacy Policy.

4 Foods to Eat While on Sulfamethoxazole/Trimethoprim

Here are some foods that are recommended for consumption while taking Bactrim.

1) Prebiotics

Prebiotic meals are beneficial for gut microorganisms and are commonly found in foods high in fiber. 

Examples of prebiotic foods include: 

  • Kefir
  • Chicory roots
  • Garlic
  • Barley
  • Bananas
  • Asparagus
  • Yogurt
  • Onion
  • Apple
  • Oats

2) Probiotics

Probiotics contribute to overall health by supporting the maintenance of healthy microbes. Probiotic foods include:

  • Yogurt
  • Kefir
  • Tempeh
  • Miso
  • Milk
  • Kimchi

3) Fermented Foods

Fermented foods containing lactobacilli help restore gut microbiota. Common examples of fermented foods are:

  • Cheese
  • Cultured milk
  • Yogurt
  • Sauerkraut
  • Kombucha
  • Fermented soybean milk
  • Kimchi

4) High Fiber Foods

Fiber-rich foods play a role in promoting the growth of healthy gut microbes. Some examples of high-fiber foods are:

  • Peas
  • Nuts
  • Whole grains
  • Beans 
  • Bananas
  • Seeds
  • Lentils
  • Broccoli
  • Apples
  • Avocados

Incorporating these foods into your diet while on a Sulfamethoxazole/Trimethoprim regimen can support your gut health and contribute to a more balanced and beneficial microbiota. 

Foods to eatFoods to avoid
ProbioticsPotassium-rich foods
Fermented foodsFood containing propylene glycol
High-fiber foodsHighly acidic foods
High-calcium foods
Fortified foods

Other Interactions With Sulfamethoxazole/Trimethoprim

Here are three interactions involving sulfamethoxazole/trimethoprim that you should be aware of. 

However, please note that this list is not exhaustive. Therefore, it’s essential to keep both your pharmacist and healthcare provider informed about all medications and supplements you are using. 


Bactrim interacts with warfarin, a commonly prescribed blood thinner. Warfarin is utilized to prevent the formation of blood clots. 

When taken together, Bactrim can intensify the blood-thinning effects of warfarin. This may lead to excessive thinning of the blood, increasing the risk of bleeding or bruising.

Using these two medications concurrently might necessitate more frequent blood tests. It’s also advisable to explore alternative antibiotics that do not interact with warfarin. 

However, if Bactrim is necessary for your condition, your doctor might consider adjusting your warfarin dosage.

Certain Diabetes Medication

Sulfamethoxazole/trimethoprim can interact with some oral type 2 diabetes medications. 

Bactrim has the potential to elevate their levels in your body. This elevation can lead to dangerously low blood sugar levels. 

Consequently, it may trigger symptoms such as shivering, dizziness, and even confusion due to low blood sugar. 

Severe complications can arise if blood sugar levels drop significantly and are not promptly addressed.

supplements for immune system

Should Bactrim Be Taken With Food?

You can take sulfamethoxazole/trimethoprim with or without food. Take this medication by mouth with a full glass of water, as instructed by your doctor. If you experience stomach upset, take it with food or milk.

What Are The Side Effects Of Sulfamethoxazole/Trimethoprim?

Common side effects of sulfamethoxazole and trimethoprim may include:

  • Nausea
  • Vomiting
  • Loss of appetite
  • Skin rash

Trimethoprim and sulfamethoxazole can have serious adverse effects. If you develop any of the following symptoms, contact your doctor right away:

  • Severe stomach ache, watery or bloody diarrhea (even if it happens months after your previous dose)
  • Yellow-colored eyes or skin
  • Any type of skin rash, no matter how mild
  • Increased or diminished urination
  • New or unusual joint pain
  • A seizure
  • Increased thirst, dry mouth, and fruity breath
  • Cough that is new or increasing
  • Fever
  • Breathing difficulties

Ben’s Beta Glucan For Immune Support

Ben’s Beta Glucan is an immune support supplement designed to reduce your chance of becoming sick, fight flu, speed up recovery after injury, and help your body maintain a healthy immune system.

immune system supplements review

Beta glucan has been extensively studied and is the most powerful natural immune booster in the world. Studies show that beta glucan can improve immune function by 400%!


If you are on sulfamethoxazole/trimethoprim or know someone who is, you need to know certain dietary restrictions and foods to avoid. 

Understanding these dietary limits will help you make informed decisions and get the most out of your treatment. 

When taking sulfamethoxazole and trimethoprim, it is best to avoid high-calcium diets, very acidic foods, citrus fruits like grapefruit and orange, and alcohol.

Explore More

bactrim for prostatitis

Is Bactrim An Effective Treatment For Prostatitis?


  1. Kemnic TR, Coleman M. Trimethoprim Sulfamethoxazole. [Updated 2022 Nov 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan.
  2. Ho, Joanne M-W, and David N Juurlink. “Considerations when prescribing trimethoprim-sulfamethoxazole.” CMAJ : Canadian Medical Association journal = journal de l’Association medicale canadienne vol. 183,16: 1851-8. 2011. doi:10.1503/cmaj.111152
  3. Clark, D. G., and M. H. Litchfield. “The toxicity, metabolism, and pharmacologic properties of propylene glycol 1, 2-dinitrate.” Toxicology and Applied Pharmacology 15.1 (1969): 175-184.
  4. Seden, Kay, et al. “Grapefruit-drug interactions.” Drugs 70 (2010): 2373-2407.
  5. Weinberg, Andrew D., Julie S. Altman, and Jean K. Pals. “Quality improvement case study: Warfarin sodium interactions.” Journal of the American Medical Directors Association 7.5 (2006): 315-318.

Top Products

Total Health


Glucose Control