The 10 Foods That Spike Blood Sugar the Most (And the Surprising Ones That Don't)

For many people living with prediabetes or diabetes, the answer lies in how different foods affect blood glucose levels. While no single food is 'good' or 'bad', some foods can cause a much faster rise in blood sugar than others. Thanks to the increasing use of continuous glucose monitors (CGMs), we're learning more than ever about how individual foods affect blood glucose. Although everyone's response is slightly different, there are some clear patterns that emerge.

Here are 10 foods that commonly cause blood sugar spikes, and a few surprises that may not be as bad as you think.

Sugary Drinks

This probably won't come as a surprise.

Fizzy drinks, energy drinks, pure fruit juices and many flavoured coffees contain large amounts of rapidly absorbing sugar with very little fibre, protein or fat to slow digestion. These are among the quickest ways to raise blood glucose levels. Better choice: Water, sparkling water, unsweetened tea or coffee.

White Breads

White bread is made from refined flour, which is quickly broken down into glucose. Many people assume toast is a light breakfast, but on its own it can produce a sharp rise in blood sugar. Try instead: Wholegrain or seeded bread paired with eggs, peanut butter or Greek yoghurt to help slow glucose absorption.

Breakfast Cereals

Many cereals marketed as "healthy" contain surprising amounts of sugar and refined carbohydrates. Even cereals that appear low in sugar can raise blood glucose rapidly because some are highly processed.

A bowl of cereal with milk often contains far more carbohydrate than people realise. Where possible aim for oats, nut based muesli or wheat biscuits.

White Rice

White rice is lower in fibre, making it easier to digest and quicker to raise blood glucose. The portion size also matters. Larger portions usually lead to larger glucose rises.

Top tip: Cooling cooked rice before reheating can increase resistant starch, which may slightly reduce the blood sugar response.

Mashed Potatoes

Potatoes are nutritious and provide vitamins, minerals and fibre. However, mashed potatoes are digested more quickly than boiled new potatoes because the cooking and mashing process makes the starch easier to absorb. Ideally go for potatoes with skins, e.g. new potatoes or jacket potato.

Pastries and Cakes

These combine refined flour, sugar and fat into one highly palatable package. Although the fat may slow digestion slightly, they still contain large amounts of carbohydrate and calories that can make blood glucose management more challenging.

Sweets and Confectionery

Chocolate bars, jelly sweets and boiled sweets are concentrated sources of sugar. These can cause rapid glucose rises, especially when eaten on an empty stomach. Top tip: give this category a wide birth!

Fruit Juice

Many people think fruit juice is equivalent to eating fruit. It isn't. Juicing removes much of the fibre while concentrating the natural sugars into a drink that's easy to consume quickly. Eating whole fruit is generally a much better choice!

Large Portions of Pasta

Pasta often has a lower glycaemic index than white bread, but portion size is key. A very large serving can still provide enough carbohydrate to produce a substantial rise in blood glucose. Interestingly, cooking pasta, cooling it and reheating it may reduce its blood sugar impact slightly because of resistant starch formation, however the portion is still key!

Takeaway Pizza

Pizza surprises many people. The crust contributes carbohydrate, while the high fat content slows digestion. This often leads to a delayed blood sugar rise that can continue for several hours after eating. This delayed spike is something many people first notice when wearing a CGM.

The Foods That May Surprise You

Not every carbohydrate-rich food causes dramatic blood sugar spikes. Some foods have much less impact than people expect:

Whole Fruit

Despite containing natural sugars, whole fruit also provides fibre, water and nutrients that slow digestion.

For most people with diabetes, whole fruit can absolutely be part of a healthy diet.

Oats

Traditional porridge oats release glucose more slowly than many breakfast cereals and can help keep you fuller for longer.

Beans and Lentils

Beans and lentils are hard to beat for blood sugar management. They're naturally low in glycaemic index, high in fibre and protein, and produce a slower, steadier rise in blood glucose. They're also incredibly cheap, versatile and filling. There's no such thing as a 'superfood', but if there were, beans and lentils would certainly be strong contenders.

Greek Yoghurt

Higher in protein and lower in carbohydrate than many flavoured yoghurts, Greek yoghurt is an excellent snack for many people. Pair it with a small handful of berries and a sprinkle of pumpkin seeds for extra fibre, protein and flavour.

What can a CGM teach you?

CGMs have transformed our understanding blood glucose management and diet. Rather than relying on averages, a CGM shows how your own body responds to meals in real time. Two people can eat the same meal and experience completely different glucose responses depending on factors such as sleep, exercise, stress, medications and insulin sensitivity. That's why there's no single perfect diet for everyone. CGMs are fantastic learning tools, but they should be interpreted alongside the bigger picture. A single blood sugar spike doesn't necessarily mean you should avoid a food forever. Instead, it's an opportunity to explore how portion size, food combinations and timing influence your glucose level patterns.

Five simple ways to reduce blood sugar spikes

• Pair carbohydrates with protein or healthy fats.
• Include plenty of fibre at each meal.
• Choose wholegrain options where possible.
• Watch portion sizes rather than eliminating foods completely.
• A 10–15 minute walk after eating can significantly improve blood glucose control.

The Take-Home Message ⭐

Managing blood sugar isn't about cutting out every carbohydrate. It's about understanding which foods have the greatest impact, choosing balanced meals and finding an approach that works for your lifestyle.

If you living with diabetes, remember that nutrition advice should always be personalised. What causes a spike in one person may have a much smaller effect in someone else. Understanding your own body's response whether through healthy eating habits, blood glucose monitoring or a CGM can help you make informed choices without unnecessary restriction.

Confused about what to eat for better blood sugar? Get in touch below, and let's create a plan that's realistic, evidence-based and works for you.