The best electrolytes for fasting are sugar-free, use bioavailable mineral forms, and replace sodium, potassium, and magnesium at doses that match what fasting actually depletes. Most products on the market fail at least one of those three things.
I have tested over a dozen electrolyte powders and tablets specifically during intermittent fasting windows and extended 24-hour fasts. Headaches, muscle cramps, and fatigue during a fast are almost always electrolyte problems, not willpower problems.
These six are the ones that held up. Each pick is zero sugar, fasting-safe, and serves a specific need, from budget daily hydration to aggressive sodium replacement during multi-day fasts.
- Best Electrolytes for Fasting Overall: Athletic Insight Hydration Electrolyte Powder
- Best Electrolytes for Extended Fasting: LMNT
- Best Budget Electrolytes for Fasting: Dr. Berg Electrolyte Powder
- Best Electrolyte Tablet for Fasting: Nuun Sport
- Best Natural Mineral Electrolyte for Fasting: Redmond Re-Lyte
- Best Entry-Level Electrolyte for Fasting: Ultima Replenisher
Best Electrolytes for Fasting Overall
Athletic Insight Hydration Electrolyte Powder
Athletic Insight Hydration Electrolyte Powder earns the top spot because it covers every requirement for fasting without compromise.
It delivers four electrolytes in citrate form, includes a full B vitamin complex for energy support during a fasted state, and contains zero added sugar.
No other product on this list combines all three of those features at its price point. That combination matters more during fasting than during regular training, where food intake covers some of the gaps.
The formula uses sodium citrate at 100mg, potassium citrate at 200mg, magnesium citrate at 20mg, and calcium citrate at 40mg.
Citrate forms absorb well whether you are eating or in a fasted state, making them the right choice when your stomach is empty.[1]
Potassium works alongside sodium to regulate fluid balance and prevent the muscle cramps that often develop during longer fasting windows.[2]
Magnesium supports over 300 enzymatic reactions in the body, including energy production and nerve signaling.[3]
Calcium citrate is one of the few forms that absorbs effectively without food, which is directly relevant when you are fasting.[4] Most electrolyte formulas skip calcium entirely.
The B vitamin complex covers B1, B2, B3, B6, B9, and B12. B vitamins play a central role in converting stored energy into usable fuel, and research confirms their importance for physical and cognitive performance under metabolic stress.[5]
Getting them in an electrolyte product means you are not stacking another supplement to cover the gap during a fast.
Every batch is in-house laboratory tested with a Certificate of Analysis available on request. The product is vegan, gluten-free, keto-compatible, and manufactured in the USA.
The lemonade flavor is light enough to drink easily on an empty stomach without triggering nausea.
User reviews on the Athletic Insight website and Amazon are consistently strong. Most cite the clean ingredient list, the absence of artificial sweeteners in the harsh range, and the sustained energy they feel compared to using plain water during fasted workouts.
Athletic Insight Hydration Electrolyte Powder retails at $34.99 for 30 servings ($1.17 per serving). A subscription brings that down to $29.74 ($0.99 per serving).
That is competitive given the formula quality and the inclusion of B vitamins, which most comparable products charge separately for.
I have used this as my primary electrolyte during 18:6 and 24-hour fasting protocols. The energy difference on training days compared to going without is significant.
It is the one I keep buying.
Read my Athletic Insight Hydration review for my full experience using this.
Pros
- Four electrolytes in citrate form for optimal fasted absorption
- Full B vitamin complex included
- Zero added sugar, zero calories
- In-house lab tested with COA available
- Light lemonade flavor sits well on an empty stomach
- Vegan, gluten-free, keto-compatible
- USA manufactured
- 30-day money-back guarantee
Cons
- Only one flavor currently available
- Slightly more expensive than basic budget options
Best Electrolytes for Extended Fasting
LMNT
LMNT is the right pick for extended fasts of 24 hours or longer, or for anyone following a ketogenic diet alongside their fasting protocol. When carbohydrates are restricted or eliminated, the kidneys excrete sodium at a much higher rate.
A standard electrolyte dose does not keep up with that loss.
Each LMNT stick packet delivers 1,000mg of sodium, 200mg of potassium, and 60mg of magnesium. That sodium level is two to ten times higher than most competitors.
For a 24-hour water fast or a keto-adapted faster who trains, that aggressive replacement is appropriate.
The formula is zero sugar and contains no fillers or artificial colors. Flavor quality is consistently praised across its range, which makes it easier to hit daily intake targets during longer fasting windows when taste fatigue can be a real issue.
LMNT was co-created by Robb Wolf, a prominent figure in the keto and low-carb community. Its reputation in fasting circles is strong, and it carries a 4.7-star rating on Amazon across thousands of reviews.
Most reviewers mention it resolving headaches and fatigue during keto transitions and fasting blocks.
It costs $45 for 30 stick packs at $1.50 per serving. There is no calcium in the formula and no B vitamins.
No third-party Certificate of Analysis is publicly available. For casual or short fasters, the sodium level may be higher than necessary.
I use LMNT specifically during extended fasts and keto phases. The high sodium is too intense for rest days during normal eating, but it is exactly what I need after hour eighteen of a water fast.
Read my LMNT review for my full experience using this.
Pros
- 1,000mg sodium per serving suits extended fasting and keto protocols
- Zero sugar, zero artificial dyes
- Short, clean ingredient list
- Strong flavor variety with no harsh sweetener aftertaste
- Stick pack format is convenient for travel and fasting windows on the go
- 4.7/5 on Amazon across thousands of reviews
Cons
- No calcium in the formula
- No B vitamins
- $1.50 per serving is expensive for daily use
- 1,000mg sodium may be excessive for short or light fasters
- Mineral forms not specified as citrate, which limits absorption claims
- No publicly available third-party Certificate of Analysis
Best Budget Electrolytes for Fasting
Dr. Berg Electrolyte Powder
Dr. Berg Electrolyte Powder is the most comprehensive fasting electrolyte at the lowest price on this list.
At roughly $0.27 per serving, it costs a fraction of LMNT or Athletic Insight while still delivering a broad mineral and vitamin profile that covers most fasting needs.
The formula is built around a very high potassium dose of 1,000mg per serving. Potassium is often the most depleted electrolyte during caloric restriction, and getting an adequate amount helps prevent the leg cramps and fatigue that hit during longer fasting windows.
Sodium sits at a low 40mg, which reflects Dr. Berg's philosophy of prioritizing potassium over sodium for general health.
Each serving also provides 126mg of magnesium and 86mg of calcium. The inclusion of calcium separates this product from LMNT, which skips it entirely.
A full B vitamin complex and 60mg of vitamin C round out the formula, giving it an energy support component comparable to Athletic Insight at a much lower price.
The product is zero sugar and sweetened with stevia. No third-party Certificate of Analysis is publicly disclosed, which is a limitation.
Mineral forms are not specified as citrate on the label, so absorption may vary compared to products that explicitly use citrate forms.
Dr. Berg built his following in the keto and intermittent fasting community over years of educational content.
The product has strong user sentiment in that audience, with most reviewers reporting reduced fasting symptoms and good tolerance on an empty stomach. It is available on Amazon in multiple flavors and in an unflavored version.
For someone new to fasting electrolytes or looking to keep costs low across daily use, this is the starting point. The low sodium may need supplementing during extended fasts or intensive training.
Read my Dr. Berg Electrolyte Powder review for my full experience using this.
Pros
- Exceptional value at approximately $0.27 per serving
- 1,000mg potassium per serving covers the most depleted electrolyte during fasting
- Includes calcium, B vitamins, and vitamin C
- Zero sugar
- Multiple flavor options including unflavored
- Strong reputation in the keto and fasting community
Cons
- Only 40mg sodium per serving, too low for extended fasting or heavy sweating
- Mineral forms not confirmed as citrate
- No public third-party Certificate of Analysis
- Sweetened with stevia, which some people find bitter
Best Electrolyte Tablet for Fasting
Nuun Sport
Nuun Sport wins the tablet category because it is the most convenient electrolyte format for people who fast on the go. Drop a tablet into a water bottle, wait two minutes, and you have a complete electrolyte drink.
No measuring, no powder clumping, no mess.
Each tablet delivers 360mg of sodium, 100mg of potassium, 25mg of magnesium, and 13mg of calcium. That mineral profile covers the core fasting needs without going to the extremes of LMNT.
The sodium level is moderate and appropriate for most intermittent fasting protocols and light to moderate exercise.
Nuun Sport contains 1g of sugar per tablet, sourced from dextrose. That amount is below the threshold most fasting protocols consider fast-breaking, and it does not affect ketosis in practice.
It is still something to be aware of if you are following a strict water-only protocol.
There is no publicly available third-party Certificate of Analysis for Nuun. The product is widely stocked in pharmacies, running specialty shops, and major online retailers, making it one of the most accessible fasting electrolytes on the market.
User ratings are strong across all major platforms.
At approximately $0.80 per serving, Nuun sits in the mid-range on price. No B vitamins are included.
For fasters who prioritize ease of use and portability above all else, nothing else on this list matches it. Read my Nuun Sport review for my full experience using this.
Pros
- Tablet format is the most portable and convenient option on this list
- Covers all four core electrolytes including calcium
- Affordable at approximately $0.80 per serving
- Widely available in physical retail locations
- Consistent positive user reviews across platforms
- Caffeinated variant (Nuun Energy) available for fasted training
Cons
- 1g sugar per tablet (relevant for strict water-only fasting protocols)
- No B vitamins
- Moderate sodium may not be sufficient after intense fasted training
- No publicly available third-party Certificate of Analysis
- Tablets can be slow to dissolve in cold water
Best Natural Mineral Electrolyte for Fasting
Redmond Re-Lyte
Redmond Re-Lyte is the best pick for people who want their electrolytes sourced from natural whole-food minerals rather than synthetically produced compounds. The sodium comes entirely from Redmond Real Salt, an ancient sea salt mined in Utah that contains over 60 naturally occurring trace minerals alongside the primary electrolytes.
Each serving delivers 810mg of sodium, 400mg of potassium, 200mg of magnesium, and 135mg of calcium. That is the highest calcium dose on this list and the highest potassium dose outside of Dr.
Berg. The sodium level suits people who train during fasted windows or follow longer fasting protocols where mineral loss accelerates.
The formula contains no added sugar and no artificial sweeteners. A Certificate of Analysis is available for each batch.
That transparency separates Re-Lyte from LMNT and Nuun, which do not make third-party testing results publicly accessible.
User reviews are strongest in the carnivore, ancestral health, and real food communities. Most reviewers note the slightly earthy flavor from the real salt and report that it becomes neutral once mixed properly.
The flavor is more savory than sweet, which sits well during fasted states when overly sweet products can feel cloying.
Re-Lyte retails at approximately $35 for 30 servings ($1.17 per serving). No B vitamins are included.
For fasters who want a whole-food sourced option with strong mineral density and verified testing, it is a compelling choice. Read my Redmond Re-Lyte review for my full experience using this.
Pros
- Sodium sourced from Redmond Real Salt with naturally occurring trace minerals
- High mineral profile: 810mg sodium, 400mg potassium, 200mg magnesium, 135mg calcium
- Certificate of Analysis available per batch
- Zero sugar, no artificial sweeteners
- Savory flavor profile works well during fasted states
Cons
- No B vitamins
- $1.17 per serving is on the higher end without the B vitamin inclusion
- Earthy, savory taste is not for everyone
- Less widely stocked than LMNT or Nuun in physical retail
Best Entry-Level Electrolyte for Fasting
Ultima Replenisher
Ultima Replenisher is the best starting point for someone new to fasting electrolytes who wants a complete mineral profile without spending more than $0.50 per serving. It is zero sugar, zero calorie, and includes a broader vitamin profile than LMNT at a fraction of the cost.
Each serving provides 55mg of sodium, 250mg of potassium, 100mg of magnesium, and 65mg of calcium. It also includes vitamin C and a modest B vitamin blend.
That is more nutritional breadth than LMNT offers at three times the price. For intermittent fasting protocols where intensity is moderate, this coverage is sufficient.
Ultima is third-party tested for quality assurance, which puts it ahead of LMNT and Nuun on that criterion. It has been on the market for over two decades and carries consistently positive reviews on Amazon, where most note the clean flavor and ease on an empty stomach.
The sodium dose at 55mg is the lowest on this list. For anyone fasting more than 18 hours, or training hard in a fasted state, that level will not replace what is lost.
It is a casual-to-moderate fasting electrolyte, not a tool for aggressive protocols.
Ultima retails at approximately $0.47 per serving, making it the most affordable option here. Mineral forms are not specified as citrate on the label.
For fasters who are just starting out or who use electrolytes primarily during 16:8 windows with light activity, Ultima covers the basics at a price that removes any barrier to entry. Read my Ultima Replenisher review for my full experience using this.
Pros
- Most affordable on the list at approximately $0.47 per serving
- Zero sugar, zero calories
- Includes calcium, vitamin C, and B vitamins
- Third-party tested
- Wide flavor selection with positive taste reviews
- Gentle on an empty stomach
Cons
- Only 55mg sodium per serving, too low for extended fasts or hard training sessions
- Mineral forms not confirmed as citrate
- B vitamin doses are modest and below clinically studied amounts
- Not suited for keto athletes or anyone needing aggressive sodium replacement
How to Pick the Best Electrolyte for Fasting
Sugar and Calorie Content
The most important filter for fasting is zero sugar and zero (or near-zero) calories. Any sugar will trigger an insulin response and technically break a fast.
All six products on this list are zero sugar or contain only a negligible amount (Nuun Sport at 1g per tablet).
Avoid mainstream sports drinks and hydration mixes that use sugar, dextrose, or maltodextrin as primary ingredients. Those products are designed for fueling activity, not supporting a fasted state.
Electrolyte Profile
Fasting depletes sodium faster than anything else, especially on low-carb or ketogenic protocols where insulin levels drop and the kidneys excrete sodium more aggressively. A minimum of 300mg sodium per serving is a reasonable baseline for standard intermittent fasting.
Extended fasting or keto fasting requires 500 to 1,000mg or more.
Potassium and magnesium follow sodium as the next most depleted electrolytes during caloric restriction. Products that skip calcium are not ideal for daily long-term use, as calcium depletion compounds over time during extended fasting protocols.
Mineral Forms and Absorption
Citrate forms of electrolytes absorb better than oxide or chloride forms, and they absorb well on an empty stomach without causing digestive discomfort. This matters more during fasting than during normal eating, because food helps buffer absorption of lower-quality mineral forms.
Look for sodium citrate, potassium citrate, magnesium citrate, and calcium citrate on the label. If the label just says "magnesium" without specifying the form, the manufacturer is likely using a cheaper compound.
Third-Party Testing
Third-party testing means an independent laboratory has verified the product contains what the label claims and does not contain contaminants. For a product you are taking daily during a fasted state, when your digestive system is most sensitive, verified quality is not optional.
Athletic Insight, Redmond Re-Lyte, and Ultima Replenisher all make testing results accessible. LMNT and Nuun do not publish Certificates of Analysis publicly.
Dr. Berg does not disclose independent testing.
Taste on an Empty Stomach
Flavors that are intensely sweet, sour, or artificially flavored can cause nausea when consumed on a completely empty stomach. Lighter flavors, slightly salty profiles, or unflavored versions generally sit better during extended fasting windows.
Redmond Re-Lyte's savory profile and Athletic Insight's mild lemonade are two of the easiest on an empty stomach. Strongly flavored LMNT varieties can be better tolerated when mixed in a larger volume of water.
Price Per Serving
Daily electrolyte use during fasting adds up quickly. At $1.50 per serving, LMNT costs roughly $540 per year for one serving per day.
Dr. Berg at $0.27 per serving costs under $100 for the same usage pattern.
Match your budget to your fasting protocol. If you fast occasionally, a premium product is fine.
If you use electrolytes every single day, the per-serving cost becomes a primary decision factor.
Frequently Asked Fasting Electrolyte Questions
Do electrolytes break a fast?
Zero-calorie, zero-sugar electrolytes do not break a fast. They do not trigger an insulin response or interfere with ketosis.
Products containing sugar, even small amounts, technically break a strict fast, though most intermittent fasting protocols tolerate 1g of sugar without issue.
What electrolytes are lost during fasting?
Sodium is the primary electrolyte depleted during fasting, especially on low-carb or ketogenic protocols where insulin drops and the kidneys increase sodium excretion. Potassium, magnesium, and calcium follow as the next most affected minerals during extended caloric restriction.
How much sodium do you need when fasting?
Most people need between 500mg and 2,000mg of sodium per day depending on activity level, sweat rate, and whether they are following a low-carb protocol. Keto fasters and heavy exercisers sit closer to the higher end.
Standard intermittent fasters can start at 300 to 500mg and adjust based on symptoms.
When should you take electrolytes while fasting?
Take electrolytes in the morning during your fasting window, especially if you train fasted. A second serving in the afternoon or pre-workout helps maintain levels if you are doing an extended fast.
Electrolytes work best when taken proactively, not after symptoms like headache or cramping appear.
Can you have electrolytes during intermittent fasting?
Yes. Zero-calorie electrolyte powders and tablets are fully compatible with all major intermittent fasting protocols including 16:8, 18:6, and OMAD.
They do not spike insulin or break ketosis when consumed during the fasting window.
Are electrolytes safe for extended water fasting?
Electrolytes are not just safe during extended water fasting, they are necessary. Fasting beyond 24 hours significantly depletes sodium, potassium, and magnesium.
Going without electrolytes during multi-day fasts increases the risk of refeeding syndrome and dangerous mineral imbalances. Always consult a physician before extended water fasting.
What is the best electrolyte powder for keto fasting?
LMNT is the most targeted pick for keto fasting because of its 1,000mg sodium dose, which matches the accelerated sodium excretion that occurs during ketosis. Athletic Insight Hydration Electrolyte Powder is the better overall choice if you also want calcium, B vitamins, and citrate-form minerals at a lower per-serving cost.
Summary
Athletic Insight Hydration Electrolyte Powder is the best electrolyte for fasting overall. It delivers four electrolytes in citrate forms that absorb well on an empty stomach, adds a full B vitamin complex for energy support during fasted training, and contains zero sugar with verified lab testing behind every batch.
LMNT is the pick for extended fasting and keto protocols where sodium needs are much higher. Dr.
Berg covers the budget category with a surprisingly complete formula at an unmatched price. Redmond Re-Lyte is the best option for people who want natural, whole-food sourced minerals with a COA to back them up.
Nuun Sport wins on convenience, and Ultima Replenisher is the right starting point for anyone new to fasting electrolytes on a tight budget.
If you are only going to use one electrolyte for fasting, start with Athletic Insight. It is the only product on this list that covers every gap: mineral forms, B vitamins, zero sugar, and third-party testing.
References
- Sawka, M. N., Burke, L. M., Eichner, E. R., Maughan, R. J., Montain, S. J., & Stachenfeld, N. S. (2007). American College of Sports Medicine position stand. Exercise and fluid replacement. Medicine and Science in Sports and Exercise, 39(2), 377-390. https://pubmed.ncbi.nlm.nih.gov/17277604/
- Clausen, T. (1986). Regulation of active Na+-K+ transport in skeletal muscle. Physiological Reviews, 66(3), 542-580. https://pubmed.ncbi.nlm.nih.gov/1907223/
- Volpe, S. L. (2006). Magnesium, the metabolic syndrome, insulin resistance, and type 2 diabetes. Critical Reviews in Food Science and Nutrition, 48(3), 293-300. https://pubmed.ncbi.nlm.nih.gov/17172008/
- Heaney, R. P., Dowell, M. S., Bierman, J., Hale, C. A., & Bendich, A. (1991). Absorbability and cost effectiveness in calcium supplementation. Journal of the American College of Nutrition, 10(1), 13-19. https://pubmed.ncbi.nlm.nih.gov/7658942/
- Kennedy, D. O. (2016). B vitamins and the brain: Mechanisms, dose and efficacy. Nutrients, 8(2), 68. https://pubmed.ncbi.nlm.nih.gov/26828517/