Frequently Asked Questions

Peptides are short chains of amino acids — the fundamental building blocks of proteins. They are commonly synthesised using solid-phase peptide synthesis (SPPS), a precisely controlled process that assembles amino acid sequences one residue at a time. The resulting material is lyophilised (freeze-dried) into a stable powder and supplied in sealed vials.

Products sold by PeptidesNextDay are not approved for human or veterinary administration.

No. They have not been evaluated by the MHRA and are not approved for human or veterinary administration. By purchasing from us, you confirm you will handle products only where lawful and appropriate, in compliance with all applicable UK regulations.

We stock peptides in a range of sizes, typically from 1mg up to 10mg per vial — with some products available in larger quantities. Sizes available vary by peptide, so please check the individual product page. If you need a specific quantity not listed, contact us and we will do our best to help.

Properly stored lyophilised peptides are stable for 24 months or more. Store sealed vials at −20°C for long-term stability, or at 2–8°C for short-term use (up to 4 weeks). Keep vials away from moisture, heat, and light.

Once reconstituted in bacteriostatic water, solutions should be refrigerated at 2–8°C and used within 28 days. Avoid repeated freeze-thaw cycles, which degrade peptide integrity over time.

This is completely normal. Lyophilised peptides are exceptionally lightweight — even a 10mg amount may appear as barely a trace of white powder or a thin film on the bottom of the vial. Product quantity is measured by mass, not by visual volume.

The absence of a vacuum seal does not indicate tampering or reduced quality — it is simply a result of the sealing method used. The peptide content is unaffected.

Please check our shop for current bacteriostatic water availability. Bacteriostatic water (0.9% benzyl alcohol in sterile water for injection) is commonly used for reconstituting peptides and can help preserve a solution for a limited refrigerated period.

If bacteriostatic water is not in stock, sterile water for injection is a suitable alternative for immediate single-use reconstitution.

Cloudiness after reconstitution can occur for several reasons. The most common is adding water too quickly — always add bacteriostatic water slowly down the side of the vial and swirl gently rather than shaking. Some peptides are naturally less soluble and may require gentle warming or sonication to fully dissolve.

If cloudiness persists, contact us with your order details. A clear solution is generally expected for correctly stored peptide products.

Where batch files, product notes, or additional documents are available, they will be shown on the product page or supplied by support on request. We do not want to imply that every item has the same level of certification.

No. Not every product includes the same level of supporting information. Where extra files are available, we will list them clearly. If you need details before ordering, contact us and we can confirm what is available for that item.

Contact us with the product name and the detail you need. We will confirm what information is currently available before you place an order.

Even with careful production, minor by-products can arise. Common examples include deletion sequences, oxidised or deamidated residues, and residual synthesis reagents such as TFA. Available product notes can vary by item.

Our standard peptide products should not be treated as endotoxin-free unless that is explicitly stated on the product listing. If you require low-endotoxin or LAL-tested peptides, please contact us before ordering so we can confirm whether suitable information is available.

We recommend PayByBank® at checkout. It works through your mobile banking app, confirms payment quickly, and does not require you to enter card or bank details on the website. Bank transfer may also be available, but it can take longer to confirm. If you have a query about payment options before placing your order, please contact our team and we will assist.

Orders placed before 2pm on a working day are processed and dispatched the same day. Orders placed after 2pm, or on weekends and bank holidays, are processed the next working day. You will receive a dispatch confirmation email with tracking information once your order has been shipped.

We process orders quickly, so please contact us immediately if you need to make a change. We will do our best to accommodate amendments if your order has not yet been packed. Once dispatched, we are unable to modify or cancel orders.

No minimum order value applies. You are welcome to order a single vial. Our flat-rate shipping covers your full order regardless of size, so ordering multiple products in one shipment is more cost-effective per item.

Yes. Quantity-based discounts are available and displayed on each individual product page — the more you order, the lower the per-unit cost. For institutional, wholesale, or ongoing supply arrangements, please contact us directly to discuss bespoke pricing.

All UK orders are shipped via Royal Mail Special Delivery Guaranteed, providing next-day delivery by 1pm with full end-to-end tracking and signature on delivery. The service also includes up to £500 of standard compensation cover.

For UK orders placed before 2pm on a working day, delivery is the next working day by 1pm as standard. Orders placed after 2pm or on non-working days are dispatched the following working day, delivering the day after. We do not dispatch on weekends or bank holidays.

All orders are packed in robust, tamper-evident packaging. Lyophilised peptides are chemically stable at ambient temperature during transit — no cold packs are required for standard UK overnight delivery. Vials are individually cushioned to prevent damage. All parcels are shipped discreetly with no external indication of the contents.

Our primary service is UK next-day delivery. For international enquiries, please contact us before ordering so we can advise on options, timelines, and any customs considerations for your destination. Import regulations for peptide products vary significantly by country — the buyer is solely responsible for ensuring compliance with local laws and any applicable duties or taxes.

Royal Mail Special Delivery requires a signature on delivery. If no one is available, the carrier will leave a notification card and retain the parcel at your local sorting office for up to 18 days for collection. You can also use your tracking number to rearrange a delivery attempt via the Royal Mail website or app.

Due to the specialist nature of peptide products, we cannot accept returns of opened or used products. However, if you receive a damaged, incorrect, or missing item, please contact us within 48 hours of delivery with your order number and photos where applicable. We will arrange a replacement or full refund as quickly as possible.

First, check your tracking number (included in your dispatch confirmation email) for the latest status. If your parcel shows as delivered but you have not received it, check with neighbours and your local Royal Mail sorting office — misdeliveries can occur.

If tracking shows no update for more than 48 hours past the expected delivery date, please contact us. We will open an investigation with Royal Mail and, once concluded, arrange a replacement or refund if the parcel is confirmed lost.

Please photograph the damaged packaging and any affected vials immediately and contact us within 48 hours of receipt. Include your order number and images in your message. We will assess the situation and arrange a replacement at no cost to you as promptly as possible.

The fastest way to reach us is via our contact page. We aim to respond to all enquiries within 2–4 hours during working hours (Monday to Friday, 9am–5pm GMT). For order-related queries, please include your order number to help us respond faster.