Replenishment Email Flow: Timing, Subscriptions + Klaviyo

Replenishment is the most natural flow a consumables brand can run. The customer bought something that runs out. They will need more. The only question is whether they buy it from you, on time, or from a marketplace when they notice the tub is empty.

Get the timing right and the replenishment flow becomes one of the highest-intent emails in your account. Get it wrong (a generic “day 30” reminder on every product) and it is noise. This guide covers consumption-based timing, the subscription upsell, and the Klaviyo build, with supplements as the worked example because it is the category where this flow matters most.

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What is a replenishment email?

A replenishment email is an automated reminder sent when a customer is likely to be running low on a consumable product, timed from their purchase and the product’s usage rate. It links straight back to the exact product and variant they bought, makes reordering one click, and often offers a subscription so they never run out again.

It is not the same as a win-back email. Replenishment reaches customers before they lapse, while they are still using the product. Win-back reaches them after they have gone quiet. A good replenishment flow means fewer people ever need the win-back flow.

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Why replenishment matters so much for supplement brands

Supplements are close to the perfect replenishment category:

• Predictable consumption. Servings per container and a daily dose give you days of supply precisely.
• Habit-dependent results. Customers who stop taking a product mid-routine often decide it “didn’t work”. A timely reminder protects the result and the relationship.
• Marketplace leakage. A customer who runs out and searches a marketplace may buy a competitor’s product listed above yours.
• Subscription fit. A daily product is the easiest possible subscription sell.

This is why replenishment is one of the core flows in our supplement email programme and in our essential flows guide.

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Consumption-based timing: the formula

Most replenishment flows fail on timing. A single delay for every product ignores the fact that a 30-serving tub and a 90-capsule bottle at two a day run out at different times.

Days of supply = (servings per container ÷ servings per day) × quantity purchased

Send the first reminder, counted from delivery, at = days of supply − reorder delivery time − buffer

The product starts running down when it arrives, and the reorder needs time to ship, so count from delivery and subtract the delivery time for the next order. If your flow triggers on Placed Order rather than a delivery event, add your usual outbound shipping time back on.

Worked examples:

Product	Daily doses per container	Qty bought	Days of supply	Delivery (days)	Buffer (days)	First reminder (days after delivery)
Protein, 30 servings, 1 scoop a day	30	1	30	4	3	Day 23
Capsules, 90 count, 2 a day	45	1	45	4	4	Day 37
Capsules, 60 count, 2 a day	30	2	60	4	4	Day 52
Greens powder, 30 servings	30	3	90	5	5	Day 80
Skincare serum, roughly 8 weeks of use	~56	1	~56	4	5	Day 47

Two refinements make the formula honest:

1. Validate with real reorder data. Pull the median days between first and second order for each product from your store data. If customers reorder a 30-day product at day 38 on average, many are not using it daily. Split the difference and test.
2. Account for quantity. Someone who bought three tubs does not need a reminder at day 23. It is one of the most common replenishment bugs.

For products with variable usage (fragrance, some cosmetics), use the reorder data instead of a formula and set a wider window.

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The replenishment email sequence

Send	Email	Job
Days of supply − delivery − buffer	”Running low?”	Reorder the exact product in one click; mention subscribe and save
Around run-out date	”Time to restock”	Stronger subscription pitch; reassurance about consistency
Run-out + 7 days	”Don’t break your routine”	Final nudge; optional incentive for subscription only

What each email should include:

• The exact product and variant, with image, deep-linked to the product page or a pre-filled cart.
• The quantity they bought last time (“Your last order: 2 × Magnesium Glycinate”).
• A clear reorder button above the fold.
• A subscription option with the real subscribe-and-save terms.
• For supplements, compliant copy: remind them about the routine, do not make new health claims.

Subject line ideas

• Running low on {{ product }}?
• Your {{ product }} is nearly finished
• Time to restock, {{ first name }}
• Don’t let your routine slip
• Never run out again: subscribe and save

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The subscription upsell

The replenishment flow is the best moment to sell a subscription, because the customer is already thinking about reordering. Converting a one-off reorder into a subscription removes the need for the reminder next time.

How to structure it:

• Email 1 leads with the one-off reorder, with subscription as a secondary option. The customer came to reorder; do not make them work harder.
• Email 2 leads with the subscription: savings, flexibility (skip, pause, cancel), and never running out.
• Email 3 is the place for an incentive, and only for subscribing, not for a one-off order.

Critical filter: exclude active subscribers from the whole flow. Subscription platforms such as Recharge create orders in Shopify, which means recurring orders can look like new purchases to Klaviyo. If you do not filter subscribers out, your most loyal customers get “running low?” emails for products that arrive automatically. Most subscription apps sync subscription status or events to Klaviyo; use them in a profile filter.

Your subscribers then need their own flows: upcoming charge reminders, skip and swap prompts, and a churn-save flow when they try to cancel.

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How to build a replenishment flow in Klaviyo

Option 1: Product-timed flow (works for every store)

1. Create a metric-triggered flow on Placed Order, or on Ordered Product if you want one branch per item (Klaviyo tracks a separate Ordered Product event for each item in an order, with its product details).
2. Add trigger splits by product name, SKU or collection, one branch per replenishable product or product group.
3. Handle quantity. On an Ordered Product trigger, split on quantity (1, 2, 3+) and scale the delay for each branch.
4. Set a time delay per branch from the formula above, adding your typical shipping time because this trigger fires at purchase, not delivery.
5. Add profile filters:
   • Placed Order zero times since starting this flow (they already reordered).
   • Not an active subscriber (property or segment from your subscription app).
   • Can receive email marketing.
6. Build the emails with dynamic product content pulled from the event, so the product and variant always match.
7. Add an SMS step for customers with SMS consent, usually on the “time to restock” message. See our email and SMS strategy.

Option 2: Predictive timing with expected date of next order

Klaviyo’s predictive analytics estimate each customer’s expected date of next order, taking into account that customer’s own order pattern and the behaviour of all your customers. To see predictive analytics, Klaviyo requires (as of September 2026):

• At least 500 customers who have placed an order (non-cancelled, non-refunded, non-zero value).
• An ecommerce integration, or placed orders sent by API.
• At least 180 days of order history, with orders in the last 30 days.
• Some customers who have placed three or more orders.

Klaviyo retrains the model at least weekly. It also warns against building flows that count down to the expected date, since repetitive messaging before each order may cause unsubscribes. The practical use: a segment of customers whose expected next order falls in the next few days, used to time a single reminder or to prioritise campaign sends.

Our view: product-timed flows are more reliable for new customers with one order. Predictive timing gets better as customers build history. Mature programmes use both: product timing for first reorders, predictive segments for repeat customers.

Option 3: A dedicated second-purchase path

For first-time buyers specifically, fold replenishment into the first-to-second purchase journey. The post-purchase flow guide shows where it sits in that sequence.

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Metrics to track

• Reorder rate within the replenishment window, compared to customers not in the flow (use a holdout if you can).
• Placed-order rate and revenue per recipient per email.
• Subscription conversions from the flow.
• Median days to reorder by product, recalculated quarterly, to keep timing accurate.
• Unsubscribe rate: a spike usually means timing is too early.

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Common replenishment mistakes

• One delay for every product.
• Ignoring quantity.
• Emailing active subscribers.
• Discounting every reorder. Customers who were going to reorder anyway learn to wait for the code.
• Linking to the homepage instead of the exact product.
• No exit on reorder, so customers who already bought get “running low?” a day later.

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Build it once, earn from it every month

A replenishment flow is the rare automation that gets better the more customers you have: more order history sharpens the timing, and every subscription it creates compounds. For supplement and consumables brands, it is one of the first flows we would fix. It also belongs in the full set of ecommerce drip campaigns, alongside cross-sell emails that introduce the next product.

If you want replenishment timing engineered product by product, with subscription logic and SMS built in, our flow automation team does exactly that, or start with a free Klaviyo audit.

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Sources

• Klaviyo Help Center: Understanding Klaviyo’s predictive analytics
• Klaviyo Help Center: Shopify data reference