When should you not eat watermelon?

Watermelon is a delicious and refreshing fruit that is enjoyed by many during the warm summer months. However, there are some instances where eating watermelon may not be advisable. This article will explore when you should avoid consuming watermelon.

If you are allergic to watermelon

The most obvious time when you should not eat watermelon is if you have an allergy or sensitivity to watermelon. Watermelon allergy symptoms can include:

  • Itchy or irritated mouth/throat
  • Hives or red bumps on the skin
  • Swelling of the lips, face, tongue, or throat
  • Cramping, diarrhea, nausea, or vomiting
  • Nasal congestion
  • Difficulty breathing

If you experience any of these symptoms after eating watermelon, you likely have an allergy and should avoid consuming it in the future. Severe watermelon allergies can even cause anaphylaxis, a life-threatening reaction that requires immediate medical attention.

If you are on certain medications

Some medications can interact with compounds found in watermelon, which could have adverse effects on your health.

One example is the anticoagulant drug warfarin. Warfarin thinning the blood and watermelon contains vitamin K, which helps blood clot. Eating watermelon while on warfarin therapy can counteract the effects of the medication.

Water pills like bumetanide and furosemide are diuretics that cause increased urination. Watermelon is also a natural diuretic due to its water and potassium content. Consuming watermelon while on these types of medications can lead to dehydration, electrolyte imbalances, and kidney problems.

Medications for erectile dysfunction like Viagra and Cialis can also interact with watermelon. That’s because watermelon contains citrulline, an amino acid that can widen blood vessels much like ED drugs. It’s best to avoid excessive watermelon intake when taking these medications to prevent dangerously low blood pressure.

Always talk to your doctor or pharmacist before consuming watermelon if you take any prescription medications to avoid complications. They can advise you on potential interactions.

If you have digestive issues

Some people with digestive problems may need to steer clear of watermelon, at least in certain scenarios.

For example, people with irritable bowel syndrome (IBS) may experience more frequent diarrhea and cramping when they eat watermelon because of its high water and fructose content. This effect can be even worse if the watermelon isn’t ripe.

Individuals with gastroesophageal reflux disease (GERD) may also want to be mindful of when and how much watermelon they eat. Watermelon’s high water content can promote reflux of stomach acid back up into the esophagus. Lying down after eating watermelon can make reflux worse.

People with diverticulitis should avoid watermelon seeds, as they could become lodged in diverticula and cause pain or blockages. Watermelon flesh is not necessarily problematic for diverticulitis, but eating it raw has caused issues for some people.

Those with digestive concerns should carefully test their tolerance for watermelon and avoid it if they experience adverse symptoms. Eating small amounts may be better tolerated.

If you have upcoming surgery

It’s generally recommended to avoid watermelon before surgery.

Watermelon can act as a natural diuretic and may interfere with pre-surgical fluid restrictions intended to avoid complications like hypotension.

There’s also some concern that watermelon could increase bleeding risk during or after surgery due to its vitamin K content. More research is needed on this specific interaction, however.

To be safe, it’s best to stop eating watermelon at least 1-2 weeks before a scheduled surgery. Check with your surgeon about any diet restrictions beforehand.

If you have kidney disease

Individuals with chronic kidney disease need to limit their potassium intake, as excess potassium can cause dangerous heart arrhythmias in those with impaired kidney function.

Watermelon happens to be one of the highest potassium-containing fruits. One cup of diced watermelon has about 270mg of potassium.

While someone without kidney issues likely doesn’t need to worry about their potassium intake from watermelon, those with kidney disease should be cautious and limit portion sizes or avoid watermelon altogether depending on the severity of their condition.

Always consult your nephrologist for advice on managing your diet with kidney disease. They can recommend appropriate restrictions.

If you have oral allergy syndrome

Some people have oral allergy syndrome (OAS) triggered by fruits like watermelon. OAS is a cross-reaction between certain proteins in fruits, vegetables, and nuts with environmental pollens like birch or grass.

With OAS, people experience minor mouth and throat irritation when they eat raw fruits and veggies they are sensitive to. However, they typically do not have a problem when the produce is cooked.

So someone with OAS related to watermelon would likely be fine eating cooked watermelon but could experience itching, tingling, or swelling in the mouth after eating raw watermelon. Avoiding raw watermelon is recommended in this case.

If you are following a low-carb or low-sugar diet

While watermelon can be enjoyed in moderation on many diets, people restricting total carbohydrates or sugars often avoid eating watermelon.

Here are the carb and sugar amounts in 1 cup of diced watermelon:

  • Total carbs: 11.5 grams
  • Sugars: 9.4 grams

The glycemic index of watermelon is high at 72-80, so watermelon can cause a spike in blood sugar. People with diabetes and prediabetes should be mindful of portion sizes for this reason.

If you’re following a very low-carb ketogenic diet or avoiding added or natural sugars for health reasons, watermelon would not fit these dietary restrictions well.

If you have overactive bladder

Some sources claim that eating watermelon can exacerbate overactive bladder symptoms like urgency and frequent urination.

This is because watermelon is a natural diuretic, so it increases urine production and could theoretically aggravate an already overactive bladder.

However, research specifically looking at watermelon’s effects on overactive bladders appears limited. Some people find they can enjoy watermelon without issues.

But if you notice your bladder symptoms consistently flare up after eating watermelon, you may want to consider avoiding it. Track your symptoms and consult your urologist or primary care doctor for advice.

If you take lithium

There are some concerns about the safety of eating watermelon if you take lithium to treat bipolar disorder.

This is because lithium toxicity is more likely when sodium levels are high. Watermelon’s potassium can decrease sodium reabsorption by the kidneys, raising sodium levels.

A few small studies found eating watermelon for a week increased lithium blood levels and caused adverse effects in some participants. More research is still needed though.

To be safe, people taking lithium to manage bipolar disorder should exercise caution with watermelon and consult their psychiatrist or pharmacist about any potential interactions.

If you have end stage renal failure and are on dialysis

Individuals with end stage renal failure who require dialysis need to follow a kidney-friendly diet that limits fluids, sodium, potassium, phosphorus, and protein.

Unfortunately, watermelon does not align well with renal diet restrictions:

  • It has high water content.
  • It is high in potassium.
  • The citrulline in watermelon can increase urine output, which dialysis patients need to limit.

For these reasons, watermelon is typically not recommended for people with renal failure on dialysis. Always consult your renal dietitian for personalized advice.

If you take tamoxifen

Tamoxifen is a medication used to treat and reduce the risk of hormone receptor-positive breast cancer.

Some early research suggests that watermelon may reduce blood levels of tamoxifen due to an interaction with certain enzymes that metabolize the drug.

However, this is not conclusively proven. More high-quality studies are still needed.

Nonetheless, people taking tamoxifen may want to exercise caution with watermelon and consult their oncologist or pharmacist about potential interactions to be safe. Limiting watermelon intake may be advised.

If you have a blood disorder

Certain blood disorders like G6PD deficiency, thalassemias, and sickle cell anemia may mean you need to limit intake of fava beans or other triggers that can induce hemolytic anemia.

There’s limited evidence that watermelon may also rarely trigger hemolytic anemia in those with underlying blood disorders.

However, this side effect seems very uncommon. More research is still needed.

Those with blood disorders should exercise general caution with watermelon, avoid eating excessive amounts, and consult a hematologist about appropriate dietary precautions.

If you have trouble managing your blood sugar

As mentioned earlier, watermelon has a high glycemic index and can rapidly raise blood glucose levels after eating.

This effect can be especially problematic for people with diabetes or prediabetes who have trouble managing their blood sugars.

Spikes in blood sugar after meals increase complications risks like nerve, eye, kidney, heart disease, and stroke.

Checking blood glucose levels before and 2 hours after eating watermelon can show if it destabilizes your blood sugar control. You may need to limit portion sizes or avoid watermelon altogether if so.

If you experience intestinal distress after eating the seeds

Most people can tolerate eating small quantities of watermelon seeds without issues.

However, some people may experience intestinal discomfort or diarrhea after eating the seeds. This is likely due to the seeds’ fiber content, as fiber can cause gas or loose stools if not introduced gradually.

If you seem sensitive to the seeds, avoid eating them or stick to just 1-2 seeds per watermelon slice. Spitting out the seeds can allow you to enjoy watermelon flesh safely.

Some also claim that swallowing crushed or whole seeds could cause an intestinal blockage. There’s limited evidence for this, but being cautious is reasonable.

If you have concerns about pesticides

Watermelon ranks fairly low on the Environmental Working Group’s “Dirty Dozen” list of produce highest in pesticide residues.

However, farmers still apply pesticides during watermelon cultivation to control pests. Residues remain on the rind and could transfer to the flesh.

Washing watermelon thoroughly before slicing can help reduce pesticide levels. However, you can’t completely remove all residues.

If you wish to minimize pesticide exposure from produce, you may want to buy organic watermelon when possible or avoid it if organic is unavailable.

If you experience adverse symptoms after eating it

At the end of the day, pay attention to how your body reacts after eating watermelon.

While watermelon is generally safe for most people, some individuals report experiencing nausea, vomiting, diarrhea, cramps, or other symptoms after eating it.

This could signal an undiagnosed watermelon allergy or intolerance. You should abstain from watermelon if it consistently upsets your stomach.


Watermelon is usually safe to consume and provides nutrition benefits like vitamins, antioxidants, and citrulline.

But in some situations, it’s better to avoid watermelon or at least exercise caution and moderate your intake. This includes if you have an underlying health condition, take certain medications, or experience adverse symptoms.

Speak to your healthcare provider if you’re unsure about the safety of eating watermelon with your particular medical history and diet restrictions. They can offer personalized advice.

Overall, being mindful of your body’s response and avoiding overconsumption can allow most people to safely reap watermelon’s refreshing, hydrating perks during the summer.

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