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Electrolytes For Fasting
Insulin is at its lowest during a fast, so sodium excretion is at its highest — and you are taking none in from food. LMNT's unflavoured stick is $69.95 for a 30-stick box, and metro shipping is free over $149.
What actually happens on a fastInsulin is the hormone that tells your kidneys to hold onto sodium — remove food and that signal disappears for as long as the fast runs.
01 — Insulin bottoms out
Within 12 to 24 hours insulin is at its floor and sodium excretion is at its ceiling.
02 — Nothing comes back in
On a normal day, food supplies sodium all day long. During a fast the intake side of the ledger is zero.
03 — Blood volume drops
Less retained sodium means less retained water, which is part of why standing up quickly can feel different on day two.
04 — Potassium and magnesium drift down
Urinary losses continue for days while intake stays at nothing, so both need topping up alongside sodium.
Daily mineral targets while fastingRanges follow Phinney & Volek's carbohydrate-restriction guidance plus the NHMRC nutrient reference values. General information for healthy adults, not medical advice — long fasts should be supervised.
Sodium
2,000–4,000 mg
Baseline from food while fasting: 0 mg. Split across two or three doses through the day.
Potassium
1,000–3,500 mg
Baseline from food while fasting: 0 mg. Lower than a fed day, but not zero on fasts beyond 24 hours.
Magnesium
300–400 mg
Baseline from food while fasting: 0 mg. An evening dose lines up with the sleep disruption longer fasts can bring.
What a signal usually reflectsNot a diagnosis — a guide to which mineral is most likely running low, and why, so you can choose what to top up.
| Signal | Likely mineral | Why it happens |
|---|---|---|
| Day-two headache | Sodium | Coincides with sodium excretion peaking as insulin bottoms out, while none is coming in from food — the signature of the insulin-driven sodium flush. |
| Light-headed standing up quickly | Sodium | Tracks with lower blood volume, which follows lower retained sodium — sodium is part of what keeps fluid in the bloodstream. |
| Restless legs or cramping at night | Magnesium | Magnesium is involved in muscle relaxation, and intake drops to zero on a fast along with every other mineral that normally comes from food. |
| Noticeable heartbeat at rest | Potassium | Potassium plays a role in heart rhythm, and urinary potassium losses continue through an extended fast even with no food intake. |
| Ongoing chills or low energy | Sodium | Consistent with lower blood volume and lower blood pressure, both downstream of sustained sodium loss during a fast. |
General physiological information, not a diagnosis. If a signal is severe, persistent, or you are on blood pressure, heart or kidney medication, stop the fast and speak with a GP rather than relying on this table.
The first 72 hoursRelative electrolyte loss across a typical 72-hour fast — indicative only, not a measured value.
0–12 h
Glycogen burning
Insulin is falling and water starts to leave with glycogen.
12–24 h
Insulin floor
Sodium excretion climbs. The first salted dose belongs here.
24–48 h
Peak loss
The classic day-two headache window. Two or three doses through the day.
48–72 h
Plateau
Losses steady but cumulative. Magnesium and potassium matter as much as sodium now.
Sodium per serve, comparedLabel values per serve as supplied by each brand. A fasting-day target of 2,000–4,000 mg sodium is hard to reach with a sports drink and impossible with coconut water.
LMNT (1 stick)
1,000 mg
Re-Lyte (1 scoop)
810 mg
Concentrated mineral drops (1 dose)
380 mg
Sports drink (600 mL)
250 mg
Coconut water (250 mL)
60 mg
Fasting friendly
Zero calories, zero sugar
No sweeteners
Nothing to raise insulin
Steady through the day
Sodium, potassium and magnesium together
Train fasted
Sodium ready for a morning session
Suggested for fastingPicked for zero calories and a format that is easy to dose in small, spread-out amounts.
LMNT Raw Unflavoured Electrolyte Mix - 30 Sticks
LMNT
$64.95
Unflavoured and unsweetened — nothing to second-guess during a fast. 1,000 mg sodium per stick.
Re-Lyte Hydration - Unflavoured - Tub - 75 Serves
Redmond
$74.95
An adjustable scoop, so you can split sodium across two or three smaller doses instead of one large hit.
CMD Concentrated Mineral Drops - 240ml
BioTrace
$49.95
A concentrated drop format — add it to plain water without the bulk ingredients a sachet carries.
Also stocked for fasting
Mineral Balance - Essential Electrolytes - 450g
Ancient Lakes
$24.95
Ocean Sourced Electrolyte Drops - 240ml
Aussie Trace Minerals
$40.95
Unflavoured - 30 Sachets
Sodii
$64.90
Keto Blend - 425g
Ancient Lakes
$24.95
ReLyte Hydration - Unflavoured - Stick Packs x 30
Redmond
$59.95
Unflavoured - 30 Serve Tub
Sodii
$59.90
Magnesium Bisglycinate - 60 Capsules
BioTrace
$44.95
Natural Liquid Magnesium - 200ml
Ancient Lakes
$49.95
Natural Liquid Magnesium - 95ml
Ancient Lakes
$34.95
Electrolyte Capsules - 100 Capsules
Vitassium
$79.95
Magnesium Enriched Natural Lake Salt. - 425g
Ancient Lakes
$18.95
Extra Strength Electrolyte Capsules - 100 Capsules
Vitassium
$89.95
Elite Ion-Power Electrolytes
BioTrace
$49.95
Fasting Drops - 250ml
Keto Chow
$42.95
Ocean Sourced Electrolyte Drops - 60ml
Aussie Trace Minerals
$21.95
Elemental Magnesium - 60mL
BioTrace
$29.95
Electrolyte Capsules - Buffered - 100 Capsules
SaltStick
$69.95
CMD Concentrated Mineral Drops - 120ml
BioTrace
$34.95
Magnesium Topical Spray - 125ml
Ancient Lakes
$29.95
Electrolyte Capsules + Caffeine - 100 Capsules
SaltStick
$79.95
Fasting Drops - 24ml - Best Before 28 Feb 2026
LYTES
$14.95
Clean Slate (Unflavoured) Electrolyte Powder - 30 Sticks
SALTT
$66.95
Electrolyte Drops - 250ml
SALTT
$39.95
Electrolyte Capsules - 240 Serves
Keto Chow
$79.95
Electrolyte Drops - 120ml
SALTT
$24.95
Not sure yet?
Three quick questions,
one recommendation
Answer three questions about how you fast and we'll point you at a pick to start with. Prefer the full version? Take the complete quiz.
How strict does your fast need to be?
How long is your typical fast?
How do you like to dose it?
Based on your answers, start with
LMNT Raw Unflavoured
the highest sodium dose, unflavoured, for a strict fast
The fast does not pause the loss.
Shop fasting electrolytesFree shipping over $149
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Fasting and electrolytes, answeredAnswers to what fasters ask us most. These same answers power the FAQ schema on this page.
Minerals carry no calories and do not raise insulin. Flavourings and sweeteners are the grey area, which is why unflavoured mixes are the safe pick.
One serve within the fasting window is usually plenty. Extended fasts past 24 hours typically need two or three, split through the day.
Too much salt in one hit can upset your stomach. Split the dose into smaller glasses across the day and drink slowly rather than taking it all at once.
Yes — insulin is the hormone that tells your kidneys to hold onto sodium, and insulin drops to its lowest point during a fast. Lower insulin means more sodium leaves in urine, even though none is coming in from food.
Check the label for sugar, maltodextrin or fruit juice — some electrolyte drinks carry meaningful calories. LYTES' fasting-friendly range is unflavoured or sweetened only with stevia or monk fruit, both zero-calorie.
Daily electrolyte minerals are food, not a medicine, so there is no upper day limit on the minerals themselves. For fasts beyond 24–48 hours, plan the fast itself with a health professional rather than relying on this page alone.
Not sure which brand suits you?
Take our quiz and we will match you to a brand and format based on how you ride, or start with a taster pack and try a few before committing to a full size.