How to Use Electrolyte Sachets Properly

Most athletes use electrolyte sachets too late, at the wrong concentration, or without any connection to what else they're fuelling with. The result is a hydration plan that looks complete on paper but underdelivers when it matters — a drink that sits heavily because it's too concentrated, fluid that passes through without being retained because sodium is too low, or a stomach that protests because the electrolyte strategy was bolted onto the fuelling plan rather than built into it.

Knowing how to use electrolyte sachets properly is less about following a generic rule and more about matching sodium delivery to the work you're asking your body to do — and when.

"When we built the truefuels electrolyte formula, the goal was to make it something athletes would actually keep drinking in the final hour of a race. That meant getting the sodium dose right for normal conditions — not the extreme-case doses you see elsewhere — and keeping the flavour clean enough that you're not fighting yourself to drink it when you most need to. The best electrolyte product is the one you'll still be using at kilometre 35."
— Alistair Brownlee, Two-time Olympic Triathlon Champion and founder of truefuels

The three-phase framework: before, during and after

Electrolyte sachets are most effective when they're planned around a session, not added reactively once things are going wrong. The practical framework is three phases: pre-loading, in-session use, and post-session recovery.

When to use electrolyte sachets — by session type

Each truefuels Active Hydration sachet delivers 390mg sodium, 150mg natural potassium, and 25mg magnesium per 500ml — calibrated to replace approximately 80% of average sodium loss per 500ml of fluid. That number is grounded in GSSI and NIH sweat science, not a marketing target.

Before exercise: pre-loading done correctly

Pre-loading with electrolytes is most valuable before long sessions, hot-weather efforts, race simulations and races themselves. The mechanism is simple: starting with properly loaded plasma sodium means your body retains fluid more effectively from the start, rather than you having to catch up mid-session.

Mix one sachet in 500ml of cold water and drink it 60–90 minutes before exercise begins. That window gives your body time to absorb the fluid and sodium without leaving you feeling overfull at the start line.

When pre-loading matters most:
- Morning training, when many athletes start slightly under-hydrated after sleep
- Travel days, when meal timing is disrupted and hydration is inconsistent
- Hot or humid race days, where sodium losses begin immediately
- Double training days, where full recovery between sessions is limited

The common mistake is pre-loading too close to the start, or drinking too much volume. If you have a sensitive stomach, keep it to one sachet in 500ml and stop 30–45 minutes before exercise begins. Practise this in training before doing it for the first time on race morning.

During exercise: match concentration to conditions

In-session use is where most questions arise — and where the most consequential errors happen.

The core principle: the sachet should always be mixed as directed. The truefuels Active Hydration formula is calibrated for 500ml of water. Mix it stronger and you raise the concentration beyond what the formula was designed for, which can reduce palatability and increase GI stress. Mix it weaker and sodium delivery per 500ml drops below the effective range.

Session length and conditions guidance:

• Under 60 minutes in cool conditions: Plain water is usually sufficient if you began well hydrated. Adding an electrolyte sachet is optional and only relevant if you're a known heavy sweater or the session is particularly intense.

• 60–90 minutes in mild conditions: One sachet is appropriate for most athletes. Take it in the bottle you carry rather than trying to drink it separately.

• 90+ minutes or warm conditions: This is where electrolyte sachets become genuinely performance-relevant. Plan for one sachet per 500ml per hour. Heavy sweaters or athletes in heat should consider whether a second sachet is appropriate based on sweat rate and conditions.

Electrolytes and gels are not separate problems. If you're taking truefuels gels alongside an electrolyte sachet, account for the sodium those gels already deliver. The 40/0.25 gel provides 98mg sodium per gel; the 40/1.0 provides 386mg. In cooler conditions with moderate sweat rates, the gel's built-in electrolytes may cover most of your sodium needs without a separate sachet. In warm conditions or for heavy sweaters, the sachet provides the additional layer.

This is the logic behind building both products as a system rather than isolated solutions.

Matching the sachet to the conditions

The biggest mistake with electrolyte sachets is treating every session identically.

Signs your current approach is off:
- Finishing sessions with a pounding headache and heavy salt staining → sodium likely too low
- Stomach feels full and sloshy mid-session despite moderate drinking → concentration may be too high, or drinking volume too high relative to effort
- Feeling briefly better after drinking then worse 15 minutes later → fluid without sufficient sodium to retain it
- Reaching for sachets after every easy 30-minute spin → unnecessary; water alone is sufficient for short, cool, low-intensity efforts

Common mistakes when using electrolyte sachets

Using them reactively. By the time you feel badly dehydrated or flat, performance has already declined. Electrolytes work best as prevention, not rescue.

Ignoring the mixing ratio. Sachets are formulated to deliver a precise sodium dose in a specific volume of water. Doubling the concentration because you want a stronger taste changes how the product behaves and may reduce how much you're willing to drink.

Separating hydration from fuelling. If you've managed sodium but neglected carbohydrate, you'll still fade. If you've loaded carbs but ignored electrolytes in warm conditions, the result is similar. Both problems look like the same symptom late in a race — that's why they need to be planned together.

Never testing in training. Race day is not the time to discover a drink concentration doesn't sit well at threshold pace. Practise with the exact sachet, exact mixing ratio and exact timing you plan to use in the race.

After exercise: when recovery use matters

Post-session use is often overlooked, but it's relevant when turnaround is short or losses were high.

If you've finished a long run in the heat, a brick session, or a race-pace workout that left you visibly depleted, an electrolyte drink returns you to normal hydration status faster than plain water alone. Sodium in the post-session drink helps the body hold onto the fluid you take in rather than passing it through.

Post-session electrolytes matter most when:
- Your next training session is within 24 hours
- Sweat losses were high (>1kg body mass loss)
- Appetite is low immediately after the session and fluid is easier to get in than food
- You're travelling between training days or recovering in a warm environment

When recovery time is adequate and you can eat and drink normally, the urgency is lower. But for athletes in heavy training blocks with back-to-back sessions, the post-session sachet often makes the following morning's session feel markedly different.

Build a protocol, not a guess

The athletes who use electrolyte sachets most effectively don't wonder whether they're working. They know how much they're taking, when they're taking it, and what it should feel like when the plan is right.

Start by testing your sweat rate in representative conditions. Set a sodium target based on your profile and the session type. Choose a mix of products that covers that target — in the case of the truefuels system, the gel's built-in electrolytes and the Active Hydration sachet are designed to work in combination rather than in competition. Track what you drink, how you feel, and whether your pace held up in the final third.

Over a few weeks, the numbers stop being estimates and start being facts. That's when a hydration plan stops being something you hope will work and becomes something you know will.

Good hydration is rarely dramatic. It's the quiet reason pace stays stable, decisions stay clear, and the final hour looks more like the first. Use electrolyte sachets with that standard in mind — not as a ritual or insurance for poor preparation, but as a precise tool that supports the work you've trained to do.