---
title: Why did my sample fail sequencing?
description: Curious why your sample failed sequencing? Learn about common reasons like too much bacteria or not enough volume, and how to resolve them.
---

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# Why did my sample fail sequencing?

A sample may not meet our quality assurance standards and cannot be sequenced for several reasons. In most cases, collecting another sample can resolve the issue.

If you provided a saliva sample, here are some common reasons why it could fail sequencing:

- **Excessive bacteria or contaminants:** Too much bacteria or food particles in saliva samples will impact sequencing. Avoid eating or drinking 30 minutes before providing a saliva sample.
- **Incorrect volume:** Providing too little or too much saliva can lead to failure. Please follow the instructions and fill the collection tube to the specified marking.
- **White blood cell issues:** Certain conditions or treatments (e.g., chemotherapy, bone marrow transplant, hematological cancer) affecting white blood cells, which contain DNA, can prevent sequencing.
- **DNA variations:** Underlying DNA variations, like an abnormal number of chromosomes, can cause sample failure.

**Important:** The Helix lab process is not intended to identify or diagnose the reasons why a sample fails. If your sample doesn’t pass our quality processes, we will let you know that it cannot be sequenced and request a new sample.

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