Does Drinking Tea Without Sugar Increase Blood Sugar?

October 19, 2025 •

4 min read

With more than 537 million adults worldwide living with diabetes, many are mindful of their glucose levels. This leads to the important question: does drinking tea without sugar increase blood sugar?

Quick Summary

Unsweetened tea, particularly green and black varieties, contains compounds that may help regulate blood sugar levels. While caffeine can cause a temporary, mild spike in some individuals, pure, unsweetened tea is a generally safe option. The polyphenols and antioxidants present in tea are associated with potential anti-diabetic effects.

Key Points

No Sugar, No Spike: Pure, unsweetened tea contains no carbohydrates or calories and does not directly raise blood sugar levels.
Caffeine's Effect: The caffeine in black, green, and oolong teas can cause a temporary, moderate increase in blood glucose in some individuals due to stress hormone release.
Polyphenol Power: Tea's antioxidant polyphenols, like EGCG in green tea, can improve insulin sensitivity and slow sugar absorption, supporting better blood sugar control.
Herbal Benefits: Many herbal teas, including hibiscus, cinnamon, and chamomile, offer anti-diabetic benefits without caffeine.
Watch for Add-Ins: Even without added sugar, milk tea can slightly affect blood sugar due to lactose. Opt for unsweetened plant-based milks or drink it alongside a meal.
Monitor Your Body: Since individual responses can vary, particularly to caffeine, monitoring your blood sugar is the best way to understand how tea affects you.
Medical Consultation: If you have diabetes or are on medication, consult a healthcare provider before regularly consuming certain herbal teas, as some may cause interactions.

The Basic Breakdown: Unsweetened Tea and Glucose

At its most basic, pure, unsweetened tea—brewed from the Camellia sinensis plant—contains no calories or carbohydrates, meaning it won’t raise your blood sugar directly. This makes it a much better choice than sugary beverages like soda, juice, and sweetened tea, which cause rapid spikes in blood glucose levels. Herbal teas, or 'tisanes', made from fruits, flowers, or spices, are also typically calorie and carbohydrate-free, provided no sweeteners are added.

The Role of Caffeine

While the tea itself doesn't contain sugar, the caffeine present in true teas (black, green, and oolong) can have an effect on blood sugar, though it's often a temporary and individualized one. Caffeine is a stimulant that can trigger a hormonal response in the body, releasing hormones like adrenaline and cortisol. These stress hormones signal the liver to release stored glucose, which can cause a temporary rise in blood sugar. It is important to remember that everyone's reaction to caffeine is different, so it's a good idea to monitor your own body's response. This effect is typically more of a concern for individuals with diabetes, whose bodies may already have difficulty managing blood glucose.

The Beneficial Impact of Polyphenols

Counterbalancing the effect of caffeine are the powerful antioxidant compounds found in tea, known as polyphenols. Green tea, for example, is rich in a catechin called epigallocatechin gallate (EGCG), which has been linked to improved insulin sensitivity and lower blood sugar levels. Black tea contains polyphenols called theaflavins and thearubigins that also have blood-sugar-lowering properties. These compounds help regulate blood glucose by:

Slowing carbohydrate absorption: Polyphenols can inhibit the enzymes that break down carbohydrates in the digestive tract, leading to a more gradual release of sugar into the bloodstream.
Improving insulin sensitivity: They may help the body's cells respond more effectively to insulin, allowing for better glucose uptake.
Reducing oxidative stress: By fighting cellular damage, antioxidants can help prevent complications associated with diabetes.

Comparing Different Teas and Their Effects

To better understand the various impacts of tea on blood sugar, consider the following comparison table. The effects listed assume the tea is consumed without any added sugar.


Tea Type	Primary Compounds	Blood Sugar Effect	Other Benefits
Black Tea	Theaflavins, Thearubigins	Can help lower blood sugar, especially after a meal. Contains moderate caffeine.	Promotes heart health and can reduce cholesterol.
Green Tea	EGCG (catechins)	May improve insulin sensitivity and lower fasting blood glucose levels. Contains less caffeine than black tea.	Rich in antioxidants, can aid in weight management and reduce inflammation.
Oolong Tea	Polyphenols, Antioxidants	May help lower blood sugar levels in people with type 2 diabetes. Moderate caffeine content.	Provides antioxidants and anti-inflammatory benefits.
Hibiscus Tea	Anthocyanins, Polyphenols	Can help lower blood sugar and improve insulin sensitivity. Caffeine-free.	May reduce blood pressure, a common complication of diabetes.
Chamomile Tea	Flavonoids, Antioxidants	May help regulate blood sugar and improve antioxidant status. Caffeine-free.	Known for its calming properties and can aid sleep.
Cinnamon Tea	Cinnamaldehyde	Can enhance insulin sensitivity and may lower blood sugar levels. Caffeine-free.	Known for anti-inflammatory properties.

The Potential Pitfalls: What to Watch For

While unsweetened tea offers many benefits, there are a few important considerations.

Herbal Tea and Medication Interactions

Some herbal teas, though beneficial for many, can interact with medications. For example, specific herbal teas like prickly pear and fenugreek may affect common diabetes medications like metformin. Always consult with a healthcare provider before adding a new herbal tea to your diet, especially if you are on medication for diabetes.

The Impact of Add-Ins

Even if you're not adding sugar, other additions can affect blood glucose. A splash of milk contains lactose, a natural sugar that can cause a slight rise in blood sugar, particularly if you're lactose intolerant or sensitive. Opting for unsweetened plant-based milk alternatives like almond or soy, or consuming the tea after a balanced meal, can help manage this effect. Pre-packaged iced teas, even if labeled “sugar-free,” may still contain artificial sweeteners or other hidden carbs, so it is crucial to check the nutrition facts label.

Conclusion

For the vast majority of people, drinking tea without sugar does not increase blood sugar. In fact, many varieties, particularly green and black teas, contain beneficial polyphenols that can actually help improve blood sugar regulation and insulin sensitivity. The primary factor to consider is caffeine, which can cause a mild, temporary spike in blood glucose for some individuals. By opting for pure, unsweetened tea and being mindful of your body's unique response to caffeine, you can enjoy this healthy beverage and reap its many potential benefits for blood sugar management.

For more information on managing type 2 diabetes, a reputable resource is the Centers for Disease Control and Prevention's dedicated section on diabetes. https://www.cdc.gov/diabetes/basics/type2.html

Frequently Asked Questions

Generally, no. Unsweetened black tea does not directly increase blood sugar. It contains compounds called theaflavins that can actually help lower blood glucose levels, particularly after meals.

For some people, especially those with diabetes, the caffeine in tea can cause a temporary increase in blood sugar by prompting the release of adrenaline. However, this effect is highly individual and not always significant.

Yes, unsweetened green tea is often beneficial for blood sugar. It contains antioxidants called EGCG that have been shown to improve insulin sensitivity and may help lower fasting blood glucose over time.

Decaffeinated tea and caffeine-free herbal teas do not contain caffeine, eliminating the potential for a caffeine-related blood sugar spike. Many herbal teas still contain beneficial compounds that support overall health.

Adding milk to tea introduces lactose, a natural sugar. While a small amount may not cause a significant spike, it can still affect blood sugar levels. For a more stable response, consider unsweetened plant-based milks or have it with a meal.

Herbal teas like hibiscus, cinnamon, chamomile, and ginger are often recommended for their potential to help regulate blood sugar levels, improve insulin sensitivity, and provide antioxidant benefits.

Moderate consumption is generally safe and beneficial. Research suggests that 3-4 cups of black or green tea per day may offer anti-diabetic properties. It is best to avoid excessive amounts of caffeinated tea.