Celsius is a zero-sugar energy drink that markets itself as a healthier alternative to competitors like Red Bull, but “healthy” is a stretch. A standard 12-ounce can contains 200 milligrams of caffeine, which is half the FDA’s recommended daily limit of 400 milligrams for adults. It has no added sugar and minimal calories, which puts it ahead of drinks like Red Bull (110 calories and 26 grams of sugar per can). But the ingredients that Celsius highlights as metabolism boosters don’t have strong evidence behind them, and the caffeine load carries real cardiovascular effects worth understanding.
What’s Actually in a Can
Celsius builds its brand around a proprietary blend it calls MetaPlus, which includes green tea extract, guarana, ginger root, and chromium. The company claims this combination accelerates your metabolism and helps burn body fat. The can is sugar-free, using the artificial sweeteners sucralose and acesulfame potassium instead.
The 200 milligrams of caffeine comes partly from guarana, a plant-based source. Unlike coffee’s caffeine, guarana releases more slowly in your body and lasts longer. That sounds like a benefit, but the Cleveland Clinic points out that it also makes it easy to consume more caffeine than you realize, since you don’t feel the full effects right away. This slow release can lead to headaches, dizziness, heart palpitations, and jitteriness, especially if you’re also drinking coffee or tea during the day. Two cans of Celsius would put you right at the FDA’s 400-milligram daily ceiling, leaving no room for any other caffeine source.
The Metabolism Claims Are Overstated
Celsius heavily promotes the idea that drinking it burns calories and boosts fat loss. A Washington State University review of the available research found “no extensive correlation” between the drink itself and weight loss. The studies supporting these claims were mostly observational, and many involved participants who were paid or self-reported their results. The review concluded that the drink’s effectiveness in promoting fat loss is “theoretically possible but requires supplementation with regular exercise and a balanced diet,” and that “standalone consumption of Celsius is insufficient for achieving the claimed results.”
Green tea extract, one of the key ingredients Celsius highlights, has shown some promise in animal studies for improving fat burning during exercise. But when researchers tested it in human cyclists, the results were underwhelming. A study published in the International Journal of Sport Nutrition and Exercise Metabolism found little benefit from green tea extract on fat oxidation or cycling performance. The researchers concluded it offered no advantage beyond what caffeine alone already provides. In other words, the caffeine in Celsius may give you an energy boost before a workout, but the added plant extracts likely aren’t doing much extra.
Cardiovascular Effects Are Real
The biggest health concern with any high-caffeine energy drink is what it does to your heart and blood pressure. A Mayo Clinic pilot study tested the effects of a single energy drink on 25 healthy young adults (average age 29) and found that systolic blood pressure increased by 6 percent after consumption, compared to 3 percent with a placebo. More striking, levels of norepinephrine, a stress hormone that increases heart rate and constricts blood vessels, jumped by nearly 74 percent after the energy drink, versus 31 percent with the placebo.
The lead researcher noted that these blood pressure increases, paired with the spike in stress hormones, “could predispose an increased risk of cardiac events, even in healthy people.” This doesn’t mean one can of Celsius will cause a heart attack, but it does mean that daily consumption adds a measurable cardiovascular burden. If you already have high blood pressure, a heart condition, or anxiety, that 200-milligram caffeine hit is worth taking seriously.
The Artificial Sweeteners Question
Celsius avoids sugar by using sucralose and acesulfame potassium. These are FDA-approved and widely considered safe in the amounts found in a single drink, but research on their effects on gut bacteria is still evolving. Lab studies have shown that both sweeteners alter the metabolism of common gut microbes. Acesulfame potassium caused the most significant changes to bacterial metabolic pathways, while sucralose had a milder impact, with treated bacteria behaving more similarly to untreated ones.
This doesn’t mean a daily Celsius is destroying your gut health. These are in-vitro findings, meaning they were observed in lab conditions rather than inside a human digestive system. But if you’re drinking one or more cans every day, the cumulative exposure to these sweeteners is something researchers are still working to understand fully.
How It Compares to Other Options
On paper, Celsius looks better than many competitors. Red Bull packs 110 calories and 26 grams of added sugar into a single can. Celsius has essentially zero of both. Other zero-sugar options like Alani Nu and Prime Energy offer similar calorie profiles, so Celsius isn’t unique in that regard, but it does sit in the lower-risk tier when it comes to sugar content.
Where things get murkier is caffeine. At 200 milligrams per 12-ounce can, Celsius is on the higher end. A typical 12-ounce cup of coffee contains roughly 120 to 150 milligrams. If your main goal is an energy boost without sugar, black coffee or unsweetened tea delivers that with fewer additives and a lower caffeine concentration. The MetaPlus blend doesn’t offer enough proven benefit to justify choosing Celsius over simpler alternatives purely on health grounds.
Who Should Be Cautious
Celsius is not recommended for children, and the company states this on its cans. Pregnant women should also avoid it, as 200 milligrams of caffeine is at or near the upper limit most guidelines suggest during pregnancy. Anyone sensitive to caffeine, prone to anxiety, or managing a heart condition should treat Celsius the same way they’d treat any high-caffeine product.
For otherwise healthy adults who enjoy the taste and want a sugar-free energy boost, an occasional Celsius is unlikely to cause harm. The problems start with daily or multi-can habits, where the caffeine adds up quickly and the long-term effects of artificial sweeteners become more relevant. If you’re reaching for it as a weight-loss tool specifically, the evidence simply doesn’t support that use. The caffeine will temporarily increase your alertness and may slightly improve workout performance, but the proprietary blend isn’t a shortcut to burning extra calories.