Is Celsius Bad for You? Caffeine, Sucralose and Who Should Skip It

Celsius is one of the best-selling energy drinks in the US. The cans say “zero sugar”, “essential energy” and talk about metabolism (how fast your body burns energy). So many people see it as a healthier choice than Monster or Red Bull. But is Celsius bad for you? It depends mostly on how much caffeine you get in a day.

The short answer: for most healthy adults, one can a day is fine. A 12 oz Celsius has 200 mg of caffeine – about two cups of coffee – plus the sweetener sucralose, but no sugar and only 10 calories. The risk comes from drinking two or more cans, mixing it with coffee, or drinking it if you’re a teen, pregnant or have heart problems. And no, it won’t melt fat.

What’s in a can of Celsius

Here is the label of Celsius Sparkling Lemon Lime (12 oz can) – other flavors are almost the same – according to Open Food Facts:

Per can (12 oz)	Amount
Calories	10
Sugar	0 g
Caffeine	200 mg
Sweetener	Sucralose
Vitamins	C, B2, B3, B5, B6, B12, biotin
Other	Taurine, guarana, green tea extract, ginger, glucuronolactone, chromium

Ingredients: carbonated water, citric acid, taurine, guarana seed extract, green tea extract, caffeine, ascorbic acid (vitamin C), sucralose, glucuronolactone, ginger root extract, calcium pantothenate, niacinamide, natural flavor, pyridoxine, riboflavin, chromium chelate, biotin, cyanocobalamin.

Celsius Essentials (16 oz) has 270 mg of caffeine. The powder sticks (“On-the-Go”) have 200 mg per stick.

How much caffeine is too much?

Caffeine is the main thing to watch. Celsius adds it three ways: pure caffeine, guarana and green tea extract. The total on the can (200 mg) includes all three.

Who	Safe limit	Celsius cans
Healthy adults	Up to 400 mg a day	2 cans = the limit
In one go	About 200 mg	1 can
Pregnant or breastfeeding	Up to 200 mg a day	1 can = the limit
Children and teens	Energy drinks not advised	0

Limits from the FDA and the European Food Safety Authority. Teens: American Academy of Pediatrics.

For comparison: a cup of brewed coffee has about 95 mg, a can of Coca-Cola about 34 mg and a 16 oz Monster 160 mg. One Celsius plus two coffees already puts you near 400 mg.

Too much caffeine can cause a fast or uneven heartbeat, jitters, anxiety, stomach upset, headaches and poor sleep. Caffeine stays in your body for hours, so a can at 4 pm can still keep you awake at midnight. In a small trial, 18 healthy young adults drank 32 oz of an energy drink on one day and a drink with the same caffeine on another day. After the energy drink, their heart rhythm changed a bit more (a longer QT interval) and their blood pressure stayed higher for longer (Fletcher et al., Journal of the American Heart Association, 2017). That’s a big dose, but it shows energy drinks aren’t just “coffee in a can”.

Is the sucralose in Celsius bad?

Celsius is sweetened with sucralose (Splenda). It’s approved in the US and EU, but newer studies raise questions:

• A lab study found that sucralose-6-acetate, a compound formed from sucralose, damaged DNA in human cells and affected gut cells (Schiffman et al., 2023). These were lab tests, not studies in people.
• In the large French NutriNet-Santé study, people who consumed more acesulfame K and sucralose had a higher risk of coronary heart disease (Debras et al., BMJ, 2022). This study watched what people ate, so it shows a link, not proof.
• The World Health Organization advises not to use sweeteners for weight control, because long-term studies don’t show they help (WHO, 2023).

One can a day is a small amount of sucralose. But if you also drink diet sodas and use sweetener packets, it adds up. Read more in our guide to artificial sweeteners.

Does Celsius really burn fat?

Celsius has long been marketed as a drink that can “accelerate metabolism” and “burn body fat”. Where does that come from?

• The studies behind it are small and paid for by the company. In one, 60 people burned slightly more calories for 3 hours after a can than after a fake drink with no caffeine (a placebo) (Dalbo et al., 2008). In another, adults who drank it daily for 28 days had small changes in fat mass (Roberts et al., 2008).
• The extra calories burned come mostly from caffeine – a strong coffee does something similar.
• The effect is small: one cookie can cancel it out.

What really works for fat loss is eating a bit less than you burn. See our guide to the calorie deficit.

Celsius vs other energy drinks

Drink	Calories	Sugar	Caffeine	Sweetener
Celsius (12 oz)	10	0 g	200 mg	Sucralose
Celsius Essentials (16 oz)	10	0 g	270 mg	Sucralose
Monster Energy (16 oz)	230	54 g	160 mg	Sugar + sucralose
Monster Zero Ultra (16 oz)	10	0 g	150 mg	Erythritol + sucralose
Red Bull (8.4 oz)	110	27 g	80 mg	Sugar
Brewed coffee (8 oz)	2	0 g	about 95 mg	None

Labels from Open Food Facts; coffee from USDA FoodData Central.

Celsius is better than sugary energy drinks for calories and sugar. But it’s one of the strongest per can. Compare all the options in our guide to the healthiest energy drink.

Who should skip Celsius

• Kids and teens – Celsius itself says the drink is not recommended for anyone under 18.
• Pregnant or breastfeeding women – one can is already the full daily caffeine limit.
• People with heart rhythm problems, high blood pressure or anxiety.
• Anyone sensitive to caffeine, or who already drinks several coffees a day.
• People who take medicines that interact with caffeine – ask your doctor or pharmacist.

How to drink Celsius more safely

1. Stick to one can a day and count your coffee and tea too.
2. Not after 2 pm, so it doesn’t wreck your sleep.
3. Don’t mix it with alcohol – caffeine hides how drunk you feel.
4. Don’t drink it to replace food or water during a hard workout.
5. If you want energy without the sweetener, plain coffee or tea gives you caffeine with nothing added.

See what’s really in your energy drink. With NutriSmart, you photograph the label or scan the barcode. The app lists the sweeteners, preservatives and colors, explains the risks of each one and gives the drink a health score out of 100. Set an alert for sucralose, and the app warns you every time a product you scan contains it.Get the app free

You can also read about sucralose and whether Diet Coke is bad for you.

The bottom line

Celsius isn’t dangerous for most healthy adults in small amounts: it has no sugar, 10 calories and some vitamins. But it has 200 mg of caffeine per can – as much as two cups of coffee – and the sweetener sucralose, and the “fat burning” effect is tiny. Keep it to one can a day, not late in the day, and skip it if you’re under 18, pregnant or have heart problems.