Watermelon has a high glycaemic index (GI) of 72–80, meaning it can raise blood sugar levels quickly. However, its glycaemic load (GL) is low, around 5–6 per serving, which minimises its overall impact on blood sugar when eaten in moderation. Here’s what you need to know:

• 1 cup (152g) of watermelon contains:
  
  • 11.5g carbohydrates
  • 9.42g natural sugars
• Portion Control: Stick to 1-cup servings to avoid spikes.
• Pairing Tips: Combine watermelon with protein or healthy fats (e.g., nuts, Greek yoghurt) to slow sugar absorption.
• When to Eat: Best consumed during or after exercise, or as part of a balanced meal.
• Health Benefits: Rich in water (92%), packed with nutrients like Vitamin C, lycopene, and citrulline, which support heart health and blood flow.

While watermelon has a high GI, its low GL and nutrient profile make it a suitable option for most diets, even for those managing blood sugar. With Vively, you can track your personal response in real time and enjoy it in moderation with confidence.

Watermelon's glycaemic index (GI) explained

Let’s dive deeper into watermelon’s glycaemic index (GI) and what it means for blood sugar. The GI measures how quickly a food raises blood sugar compared to pure glucose, which has a GI of 100.

GI and GL numbers for watermelon

Watermelon’s GI falls between 72 and 80, categorising it as a high-GI food. However, its glycaemic load (GL) - a measure that factors in portion size – remains low.

These figures provide a clearer picture of how watermelon affects blood sugar, but there’s more to consider.

Want to learn more about how different foods affect blood sugar? Explore our full guide on the glycaemic index and what it means for your health.

Beyond GI: other blood sugar factors

Although watermelon has a high GI, its overall impact on blood sugar is influenced by additional variables. Harvard Health explains:

Watermelon's high water content - 92% - dilutes its carbohydrate density, making it less sugar-heavy than other fruits like red grapes (16% sugar) or mangoes (13%).

Here are three factors that influence watermelon's effect on blood sugar:

• Portion size: A 1-cup serving contains 11.5 g of carbohydrates.
• Food combinations: Pairing watermelon with protein or healthy fats can slow sugar absorption.
• Individual response: Factors like metabolism and activity levels play a role in how your body handles the sugar.

To better manage blood sugar, consider pairing watermelon with foods rich in healthy fats, fibre, or protein - like a handful of nuts or seeds. This combination can help slow down sugar absorption. These insights set the stage for discussing glucose monitoring data later.

Blood sugar changes after eating watermelon

Watermelon can cause a mild blood sugar rise, especially if eaten in large amounts or on its own. Pairing it with other foods helps reduce the impact.

CGM measurements of watermelon impact

Data from continuous glucose monitoring (CGM) shows that watermelon's effect on blood sugar is closely tied to portion size. Individual responses also vary depending on factors like meal composition and metabolism. This underscores the importance of portion control and pairing watermelon with other foods to manage blood sugar levels effectively.

What influences your glucose response

Several factors play a role in how your body reacts to watermelon:

Physical activity
Exercise can enhance your body’s ability to process natural sugars, especially if you eat fruits like watermelon around the time of your workout.

Meal composition and timing
Eating watermelon as part of a balanced meal can help moderate your glucose response. Pairing it with protein and healthy fats - like in a Watermelon, Feta, and Basil Quinoa salad - slows down sugar absorption.

Individual factors
Your baseline blood sugar levels, insulin sensitivity, and digestive health all influence how your body handles the natural sugars in watermelon.

Here are some practical tips for managing blood sugar when eating watermelon:

• Start with a 1-cup serving (152 g) to gauge your response.
• Use CGM technology to monitor how your blood sugar reacts.
• Pair watermelon with protein or healthy fats in a balanced meal.
• Opt for whole watermelon instead of juiced forms.

Although watermelon has a high glycaemic index (GI) of 72–76, its low glycaemic load (GL) of about 5–8 per serving makes it a good option for moderate consumption as part of a balanced diet.

Curious about fruit choices that won't spike your glucose? Discover the best 10 low GI fruits to support healthier blood sugar levels.

Health benefits of watermelon

Watermelon is more than just refreshing. It is rich in vitamin C, lycopene and citrulline, which support hydration, heart health and overall wellbeing.

Nutrients and vitamins in watermelon

Watermelon isn't just a refreshing summer snack - it’s packed with nutrients that contribute to overall health. A single cup (152 grams) of diced watermelon offers a variety of essential nutrients while being low in calories.

One standout compound in watermelon is citrulline, which plays a role in improving blood flow and regulating blood pressure. Additionally, watermelon boasts the highest lycopene content among fresh fruits and vegetables, offering strong antioxidant properties.

Beta-cryptoxanthin in the fruit helps reduce joint inflammation, while vitamins A and C are key for maintaining healthy skin and a robust immune system. Together, these nutrients not only promote overall wellness but also help stabilise blood sugar levels.

Want to support long-term health and energy? Learn how optimising glucose can promote longevity, inspired by Blue Zone habits.

Watermelon vs. processed sweets

When it comes to satisfying your sweet tooth, watermelon is a far better choice than processed treats. For example, a cup of ice cream contains about 300 calories with little nutritional value, whereas a cup of watermelon has only 46 calories and is free of fat and cholesterol.

Thanks to its high water and fibre content, watermelon slows the absorption of sugar, making it a more balanced option compared to processed sweets. Its rich antioxidant profile, especially lycopene, may also lower the risk of diabetes complications and improve heart health.

Pairing watermelon with protein and healthy fats during meals can further support blood sugar control.

Looking for low GI foods to support better glucose control? Discover the top 10 options for more stable blood sugar levels.

How to eat watermelon without sugar spikes

To avoid sugar spikes, stick to small portions of watermelon and pair it with protein or healthy fats. Timing it around meals or exercise can also help.

Recommended serving sizes

Keeping portions in check is key to managing blood sugar when enjoying watermelon. For reference, one cup (152g) of diced watermelon contains 9.42g of natural sugar and 11.5g of carbohydrates.

Here's a quick breakdown of portion sizes:

These measurements can guide you in choosing portions that work best for blood sugar control.

Best food combinations

What you eat with watermelon can make a big difference in how it affects your blood sugar. Pairing it with foods rich in protein or healthy fats can help slow sugar absorption and reduce spikes. Here are some pairing ideas:

Protein pairings:

• A serving of full-fat Greek yogurt topped with diced watermelon
• A small handful of almonds or walnuts
• String cheese or a scoop of cottage cheese

Healthy fat pairings:

• Slices of avocado
• A tablespoon of almond butter
• A sprinkle of pumpkin or sunflower seeds

Best times to eat watermelon

When you eat watermelon can also influence how it impacts your blood sugar. Timing your intake around certain activities or meals can help your body process the sugars more efficiently:

• During or after exercise: Physical activity enhances your body’s ability to handle carbohydrates, making this a great time to enjoy watermelon.
• With a balanced meal: Combine watermelon with protein and healthy fats, like adding it to a yoghurt bowl for breakfast or tossing it into a salad with grilled chicken for lunch.‍
• Spread out portions: Instead of eating a large serving all at once, divide it into smaller portions throughout the day to keep blood sugar levels steady.

Vively CGM program for understanding your fruit response

The glycaemic index is a helpful guide, but it does not always show the full picture. With Vively’s continuous glucose monitoring, you can see exactly how different fruits affect your own blood sugar in real time.

In this example, watermelon led to a higher glucose spike, reaching 7.2 mmol/L, while apple caused a lower rise at 6.1 mmol/L. This reflects watermelon’s high glycaemic index and shows why personalised tracking matters.

Using Vively, you can

• See how your favourite fruits affect your glucose response
• Learn how food combinations impact your blood sugar
• Track your Metabolic Health Score over time
• Get expert guidance from a dietitian inside the app

Rather than relying on generic advice, Vively gives you real insights so you can make better decisions about fruit, blood sugar and your overall health.

Common myths about watermelon and blood sugar

There are plenty of myths about watermelon and blood sugar, but the truth is it can be part of a balanced diet when eaten in moderation and paired wisely.

Watermelon safety for diabetes

Yes, watermelon can absolutely be part of a balanced diet for those managing blood sugar. Since it's about 92% water, the sugar is naturally diluted.

For example, a medium slice (286 g) contains about 17.7 g of sugar, which is relatively modest. While watermelon has a high glycaemic index (GI), its glycaemic load (GL) is low, meaning moderate portions won't cause a major blood sugar spike.

This sets the foundation for clearing up some common misunderstandings about watermelon and its impact on blood sugar.

Facts vs. myths: watermelon and blood sugar

Let’s tackle a few popular myths and the facts that debunk them:

Although watermelon’s GI might seem concerning at first glance, its low GL ensures it has a mild effect on blood sugar. Plus, research highlights that different fruits have varying impacts on blood sugar management. Interestingly, watermelon contains compounds like citrulline that may even support metabolic health.

Here are some tips for enjoying watermelon while managing blood sugar:

• Opt for fresh watermelon and keep an eye on your glucose response.
• Space out your fruit servings throughout the day.
• Include watermelon as part of your daily fruit intake, aiming for up to three servings per day

Conclusion

When you look past watermelon's high glycaemic index, its low glycaemic load and high water content start to shine as reasons why it can be a smart choice for managing blood sugar. In fact, research from 2021 highlights that some watermelon varieties have a GI as low as 50, showing that not all watermelons affect sugar levels the same way. This opens the door to smarter eating strategies.

A typical 1-cup serving (152g) of watermelon contains 9.42g of sugar and 11.5g of carbohydrates. Because of this, managing portions is essential - and Continuous Glucose Monitoring (CGM) can help tailor these choices to your unique needs.

Combining this with strategies like pairing watermelon with protein and timing it around physical activity can make a big difference in glucose management.

Here are a few practical tips to keep in mind:

• Pair with protein: Add something like Greek yogurt to slow sugar absorption.
• Eat around activity: Having watermelon before or after exercise can help your body process the carbs more effectively.
• Use Vively’s CGM insights: Monitor your blood sugar response to understand how watermelon fits into your diet.‍
• Stick to fresh options: Fresh watermelon is better than processed versions, as it retains compounds that support metabolic health.

"Even high-GI fruits like watermelon can fit into a balanced diet when portioned well and paired with the right foods. With personalised tracking, you can enjoy what you love while keeping your glucose in check." -- Charlotte Battle, APD and Vively's lead dietitian

FAQs

How can I eat watermelon without causing a blood sugar spike?

To enjoy watermelon while keeping your blood sugar levels steady, try pairing it with foods rich in protein or healthy fats. For instance, enjoy your watermelon with a small handful of nuts, a slice of cheese, or a serving of yoghurt.

These additions can help slow down how quickly the sugar from watermelon enters your bloodstream, making it easier on your system.

Another important tip is to practise moderation. Stick to about 1 cup of diced watermelon per serving. This portion offers plenty of hydration and nutrients without overloading your body with sugar. Including watermelon as part of a well-rounded diet allows you to savour its natural sweetness while keeping your glucose levels in check.

How can pairing watermelon with protein or healthy fats help manage blood sugar?

Pairing watermelon with protein or healthy fats is a smart way to keep blood sugar levels steady. Watermelon has a high glycaemic index (GI), which means it can cause a quick glucose spike if eaten on its own. However, when you combine it with foods like nuts, seeds, or yoghurt, the digestion and absorption of its natural sugars slow down. This helps reduce the chances of sudden blood sugar spikes.

On top of that, adding protein and healthy fats to your snack or meal can help you feel satisfied for longer, making it easier to manage portion sizes. This way, you can enjoy the sweet, refreshing flavour of watermelon while supporting balanced blood sugar and maintaining better metabolic health.

Can people with diabetes eat watermelon without worrying about blood sugar spikes?

Yes, people with diabetes can include watermelon in their diet, but keeping an eye on portion sizes is crucial. Watermelon has a high glycaemic index (GI) of 72–76, but its glycaemic load (GL) is relatively low – about 5 per ½ cup (roughly 4 ounces). This means that when eaten in moderation, watermelon is unlikely to cause significant blood sugar spikes.

To minimise any potential impact on blood sugar, try pairing watermelon with foods that are rich in protein or healthy fats, like nuts or a dollop of yoghurt. This combination can help slow the absorption of sugars. Always keep track of how your blood sugar responds and consult your healthcare provider for advice tailored to your needs.