# Biological substances (diagnostic specimens) — Postal shipping restrictions by item category

For Biological substances (diagnostic specimens), carrier is Royal Mail / Parcelforce; restriction type is restricted; scope is UK (Post Office counter); conditions is Total sample volume/mass in any parcel must not exceed 50ml/50g; must be posted in packaging complying with Packaging Instruction 650, such as the Safebox product, recorded from its source on 2026-08-10.

- **Item category:** Biological substances (diagnostic specimens) _(verified: appears in the quote below)_
- **Carrier:** Royal Mail / Parcelforce _(our reading, not quoted from the source)_
- **Restriction type:** restricted _(our reading, not quoted from the source)_
- **Scope:** UK (Post Office counter) _(our reading, not quoted from the source)_
- **Conditions:** Total sample volume/mass in any parcel must not exceed 50ml/50g; must be posted in packaging complying with Packaging Instruction 650, such as the Safebox product. _(verified: appears in the quote below)_

## What the source says

> Packaging guidelines: The total sample volume/mass in any parcel must not exceed 50ml/50g. All biological substances must be posted in packaging that complies with Packaging Instruction 650, such as our Safebox product.

## Source

- https://corporate.postoffice.co.uk/media/w5dlus1c/foia-response_foi2025_00179_appendix-d_rm-dangerous-goods-and-prohibited-and-restricted.pdf

Last verified: 2026-08-10. Review by: 2027-08-10.
Part of [Postal shipping restrictions by item category](https://referencesource.org/shipping-restrictions-by-class/).