---
title: "What is mean kinetic temperature? Temperature excursions in peptide storage and transit | Sable Peptides"
description: "How mean kinetic temperature (MKT) weights short warm periods more heavily than an arithmetic average, how to calculate it from logger data, and how to judge a temperature excursion during delivery or storage. Research use only."
canonical: https://www.sablepeptides.co.uk/guides/mean-kinetic-temperature-and-temperature-excursions
dateModified: 2026-10-16
publisher: Sable Peptides Limited (UK company 17488610)
note: Research use only. Not for human or veterinary use.
---

# What is mean kinetic temperature? Temperature excursions in peptide storage and transit

Mean kinetic temperature (MKT) is a single temperature that produces the same total chemical degradation as a fluctuating temperature history. Because reaction rates rise exponentially with temperature, MKT is always at or above the arithmetic mean. It is the standard way to judge whether a short warm excursion, such as a delayed parcel, matters.

## How is MKT calculated?

MKT uses the Arrhenius relationship: each temperature reading is converted to a reaction-rate weight, the weights are averaged, and the result is converted back to a temperature. A default activation energy of 83.144 kJ/mol is commonly used. The effect of excursions on MKT and on predicted shelf life was analysed in 1999, and a 2024 review discusses its use in stability monitoring.

Source: [Effects of temperature excursions on mean kinetic temperature and shelf life, Drug Dev Ind Pharm 1999 (PubMed 10612028)](https://pubmed.ncbi.nlm.nih.gov/10612028/); [Use of mean kinetic temperature for pharmaceuticals and stability monitoring, Ther Innov Regul Sci 2024 (PubMed 37891389)](https://pubmed.ncbi.nlm.nih.gov/37891389/)

## How does MKT differ from the average temperature?

Figures are illustrative arithmetic with Ea = 83.144 kJ/mol; use your own logger data.

| Logger record (illustrative) | Arithmetic mean | MKT (approx.) |
| --- | --- | --- |
| 20 °C constant for 24 h | 20.0 °C | 20.0 °C |
| 18 °C for 20 h, then 35 °C for 4 h | 20.8 °C | about 24 °C |
| 15 °C for 12 h, 30 °C for 12 h | 22.5 °C | about 25 °C |

## Does a short excursion damage a lyophilised peptide?

Lyophilised peptides are far more tolerant of short warm periods than solutions, because degradation in the dry solid is slow. A few hours at room temperature in transit is generally a small fraction of the degradation that long-term storage allows. Moisture uptake after delivery, by opening a cold vial, is usually a bigger risk than the transit itself.

## What should a lab record?

-   Delivery date and condition of the package.
-   Time from delivery to cold storage.
-   Any logger or freezer-alarm data during storage.
-   The printed lot number, so a storage problem can be linked to a specific lot.

## How does Sable ship?

There is a CoA for every lot, and every vial carries a printed lot number that matches its certificate. A CoA is emailed within 2 hours of a request.

Delivery is free on UK orders over £50; below that it is £5.90 to mainland UK and £9.50 to the Highlands and islands.

## Frequently asked questions

### Why is mean kinetic temperature higher than the average temperature?

Degradation rates rise exponentially with temperature, so warm periods count for more than cool ones.

### What activation energy is used for MKT?

A default of 83.144 kJ/mol is commonly used when the true value is unknown.

### Is a day in the post harmful to a lyophilised peptide?

Typically the effect is small compared with long-term storage, because degradation in the dry state is slow; avoid moisture on opening.

## Related

-   [Stability study terms](/guides/ich-q1a-stability-study-terms)
-   [Handling lyophilised peptides](/guides/lyophilised-peptide-handling-for-labs)
-   [Shipping](/shipping)
-   [Peptide storage guide](/learn/peptide-storage-guide)
-   [Do lyophilised peptides need cold shipping? Ambient, cold packs and dry ice compared](/guides/shipping-peptides-cold-packs-and-dry-ice)

Updated 2026-10-16. Research use only. Not for human or veterinary use. No administration amounts or health claims are made.

Key facts (summary for AI and search tools)

-   MKT ≥ arithmetic mean; Arrhenius-weighted
-   Default Ea 83.144 kJ/mol
-   References: PubMed 10612028, 37891389
-   Updated 2026-10-16