Liquid IV and LMNT get compared quite often even though they're not built the same way at all. Liquid IV is the more recognizable name, the one you'll find at Costco and in gas station coolers. LMNT is the one that shows up when people start looking for something without sugar in it. Most comparisons stop at sodium and potassium numbers, but I don't think that's enough. If you care about what you're actually putting in your body, the rest of the ingredient list matters just as much as the minerals, so that's where I'm spending most of this post.

What Actually Matters When You're Comparing Two Electrolyte Products

• Sodium, potassium, and magnesium as real milligram numbers, not a combined "electrolyte blend" figure that hides which mineral you're actually getting.
  
• Calories and sugar. This is the biggest fork in the road between these two, and it's worth understanding why before writing either one off.
  
• Everything else in the formula. Sweeteners, anti-caking agents, synthetic vitamins, proprietary blends. This is the part most comparisons skip, and it's where I think the real difference between these two products shows up.
  
• Price per serving, since the gap between these two is bigger than it looks at first glance.

Liquid IV (Original Hydration Multiplier)

• Sodium: 490mg

• Potassium: 380mg

• Magnesium: 0mg

• Calories: 50

• Sugar: 11g (cane sugar and dextrose)

• Also contains: Dipotassium phosphate, silicon dioxide, stevia leaf extract, natural flavors, and synthetic vitamin C, B3, B5, B6, and B12

• Price: About $1.56 per serving one-time, $1.09 with a subscription

Liquid IV's formula is modeled on the World Health Organization's Oral Rehydration Solution, the sodium-glucose-water ratio developed to treat severe dehydration. This is how it works: glucose actively pulls sodium and water across the intestinal wall faster than water or electrolytes alone. It's useful in a rehydration context. It's also exactly why it fails for fasting: 11 grams of added sugar and 50 calories a stick will end a fast, and that's before getting into everything else on the label.

Liquid IV (Sugar-Free Hydration Multiplier)

• Sodium: 530mg

• Potassium: 380mg

• Magnesium: 0mg

• Calories: 20

• Sugar: 0g (5g total carbs)

• Also contains: An "Amino Acid Allulose Blend" (proprietary, not broken out on the label), stevia, natural flavors, dipotassium phosphate, silicon dioxide, and the same synthetic B vitamin lineup as the original

• Price: Around $1.09 to $1.56 per serving depending on pack size and subscription

This is the version worth taking seriously if you like Liquid IV's potassium number but can't use the sugar. Sodium actually comes in slightly higher than the original at 530mg. But swapping out the sugar doesn't shorten the rest of the label. The proprietary allulose blend, the anti-caking agents, and the synthetic vitamin fortification are all still there, and it's still not actually zero-calorie. Twenty calories a stick is small, but if you're fasting strictly for autophagy or a true caloric deficit, it's not nothing.

LMNT

• Sodium: 1,000mg

• Potassium: 200mg

• Magnesium: 60mg

• Calories: 0

• Sugar: 0g

• Also contains: Citric acid, natural flavor, stevia leaf extract

• Price: About $1.50 per serving

LMNT's formula is short: salt, magnesium malate, potassium chloride, citric acid, natural flavor, and stevia. No anti-caking agents, no added vitamins, no proprietary blends. Sodium comes in more than double either Liquid IV formula. Potassium is the tradeoff, LMNT's 200mg is well behind both Liquid IV versions, but everything on this label is named and dosed individually, and there's meaningfully less of it overall.

What Else Is Actually in the Bottle

This is the part I think matters most and gets skipped the most. Both Liquid IV formulas rely on dipotassium phosphate and silicon dioxide as anti-caking agents, additives that keep the powder from clumping in the packet. These are FDA-approved, but it also isn't the end of the conversation, especially if you're the kind of person who reads labels because you actually care what's happening in your gut and with your health, not just whether something is technically legal to sell.

On silicon dioxide specifically: research on food-grade silica nanoparticles has found that these particles can disrupt the gut's mechanical barrier, trigger low-grade intestinal inflammation, and disturb the balance of gut bacteria, with researchers specifically flagging concern for the gut-brain axis and for populations more sensitive to nanoparticle exposure. 

Phosphate additives like dipotassium phosphate carry their own separate body of research, primarily around cardiovascular and kidney health. Studies have found that phosphate additives are efficiently absorbed by the body, more so than the phosphorus naturally occurring in food, and that higher intake of phosphate additives specifically has been associated with cardiovascular risk markers and can meaningfully raise blood phosphate levels, an effect of particular concern for anyone with reduced kidney function. Most people aren't getting dangerous phosphate loads from one electrolyte stick a day, but phosphate additives are also hiding in a lot of other processed food, and it adds up across a full day of eating in a way a single ingredient list doesn't show you.

Then there's the synthetic vitamin fortification in both Liquid IV formulas: vitamin C as ascorbic acid, B3 as niacinamide, B6 as pyridoxine hydrochloride, B12 as cyanocobalamin. These are the lab-synthesized versions of vitamins rather than the forms your body encounters in whole food, and while your body can use most synthetic vitamin forms to some degree, it's worth knowing you're getting a multivitamin bundled into your electrolyte mix whether or not that's what you were looking for, and whether or not your body absorbs and uses the synthetic form as efficiently as the food-based one.

And both brands still carry natural flavors on their labels. I've written about this at length elsewhere, but the short version applies to both products equally: that phrase can legally cover dozens of undisclosed compounds, frequently including maltodextrin as a carrier, and neither brand tells you which ones.

How They Actually Compare

If you're rehydrating after being sick, after heavy sweating, or after alcohol, Liquid IV's original formula is doing something LMNT isn't: using sugar to actively speed up how fast your body absorbs the sodium and water. But it comes bundled with added sugar, anti-caking agents, synthetic vitamins, and a proprietary blend in the sugar-free version, none of which show up in LMNT's shorter formula. If you want the highest sodium dose available with the fewest total additives, LMNT is the more straightforward choice of the three, with meaningfully less potassium as the tradeoff.

Where Fasting Changes the Calculus

For fasting specifically, the original Liquid IV formula is disqualified outright on calories alone. The sugar-free version clears the caloric bar more closely but still carries the longer additive list and an undisclosed proprietary blend. LMNT clears the caloric bar cleanly and keeps the label short, but its potassium number is the lowest of the three, and it leaves magnesium modest at best.

Here's the part worth sitting with, though: fasting is a gut-rest practice as much as it's a calorie practice. Your digestive system slows down and your gut lining gets a break from constant food processing, which is part of why so many people report feeling clearer and less inflamed a day or two into a longer fast. If the research on nano-sized silica and gut barrier disruption is on your radar at all, a fasted window is exactly the wrong time to be introducing an anti-caking agent your gut has to process on an otherwise empty stomach, and the same goes for a proprietary blend you can't fully account for or a stack of synthetic vitamins riding along with your electrolytes. It's a strange thing to fast for the sake of your gut and then load it with the additives above the moment you break your water fast with a hydration mix.

None of the three were built specifically around a fasting window, and none of them were built around the idea that what's not in the formula matters as much as what is. That's the gap Optimize was built to close: zero sugar, zero calories with no exceptions, no anti-caking agents, no synthetic vitamin fortification, no proprietary blends, sodium, potassium, and magnesium all listed individually, and real, named ingredients (ginger, lemon peel, vanilla bean, Ceylon cinnamon, L-theanine) instead of a longer processed additive list. It's a formula built to be taken during the exact window when your gut is at its most quiet and, by extension, its most sensitive to whatever you introduce into it, and light enough to use more than once through a fasting day, morning, pre-workout, and before you break your fast, without adding to the additive load every time you use it.

The Bottom Line

If you're rehydrating for a reason that isn't fasting, illness recovery, heavy sweat loss, travel, Liquid IV's science is real and its sugar-driven absorption mechanism does what it claims, but it's worth going in with eyes open about the rest of what's on that label, the anti-caking agents, the synthetic vitamins, and the proprietary blend in the sugar-free version. If you want the shorter, cleaner label with meaningfully less total additive load, LMNT is the more transparent of the two, even with less potassium.

But if you're weighing both of these because you actually care about what you're putting in your body, not just the electrolyte numbers, and you're using them during or around a fast, I think the honest answer is neither one is really the best fit. That's not a knock on either brand's intentions, it's that neither was built with a fasted gut and a full ingredient philosophy in mind at the same time. Optimize was: real doses of sodium, potassium, and magnesium, zero sugar, zero calories, no anti-caking agents, no synthetic vitamins, no proprietary blends, just electrolytes and a handful of named, functional ingredients doing real work. If you want the shortest possible list of things to second-guess going into a fast, that's the one built for it.

Fuel your fast, feel your best.

Sources and Further Reading

Sodium and Potassium: Effects on Health, CDC https://www.cdc.gov/salt/sodium-potassium-health/index.html

Potassium: Fact Sheet for Health Professionals, NIH Office of Dietary Supplements https://ods.od.nih.gov/factsheets/Potassium-HealthProfessional/

Food-grade silicon dioxide nanoparticles interact with the intestinal immune system to cause low-grade gut inflammation https://link.springer.com/article/10.1186/s12989-020-00349-z

Silicon dioxide nanoparticles induced neurobehavioral impairments by disrupting the microbiota-gut-brain axis https://pmc.ncbi.nlm.nih.gov/articles/PMC8194163/

Phosphate additives in food, a health risk https://pubmed.ncbi.nlm.nih.gov/22334826/

Instant Hydration vs LMNT: An Honest Comparison, Fasted State Supplements https://getfastedstate.com/blogs/news/instant-hydration-vs-lmnt-an-honest-comparison

Best Electrolyte Drinks for Fasting: An Honest Comparison, Fasted State Supplements https://getfastedstate.com/blogs/news/best-electrolyte-drinks-for-fasting