Stool testing is a standard procedure for diagnosing gastrointestinal diseases, parasitic infections or dysbacteriosis. But what to do if the material was collected in the evening, but the laboratory accepts it only in the morning? Is it possible to store feces in the refrigerator, and if so, for how long? The answers to these questions depend on the type of analysis, storage conditions and even on the container you use.
In this article we will analyze exact periods for storing stool in the refrigerator for different types of studies (coprogram, for worm eggs, for occult blood, PCR, etc.), we will tell you how to properly prepare the sample so as not to distort the results, and list common mistakes, due to which the analysis may be unreliable. You will also learn which containers are suitable for storage and which are not, and what to do if too much time has passed.
Important: rules may vary depending on the requirements of a particular laboratory. If you have a memo from the clinic, follow it first. If not, our recommendations will help you avoid typical mistakes.
Why you can’t store stool for too long: what happens to the sample?
Stool is not just waste, but a complex biological environment in which chemical and microbiological processes continue after defecation. At room temperature:
- 🦠 Bacteria multiply —some microorganisms (for example, E. coli) double the population every 20–30 minutes, which distorts the results for dysbacteriosis.
- 🔬 Enzymes are destroyed —for example, trypsin and lipase, which are checked during coprogram, lose activity after 4-6 hours.
- 🩸 Red blood cells are hemolyzed - if the test for occult blood, through Within 12–24 hours, it will become impossible to determine its traces.
- 🧬 DNA of parasites degrades —for PCR diagnostics it is critical to preserve chains of nucleic acids, which decay if stored incorrectly.
The refrigerator slows down these processes, but does not stop completely. The optimal temperature for short-term storage is +2…+8°C (standard refrigerator mode). Use a freezer cannot: when frozen, cells are destroyed, and the analysis becomes uninformative.
⚠️ Attention: If you donate feces for bacteria (for example, for detection Salmonella or Shigella), store it for longer than 2-3 hours even in the refrigerator useless - many pathogens die when cooled. Such an analysis is collected immediately before delivery to the laboratory.
Stool storage periods in the refrigerator for different tests
The time during which feces can be stored depends on the purpose of the study. Below are current recommendations for the most common tests (data are based on clinic protocols Invitro, Helix i Hemotest).
| Type of analysis | Maximum shelf life in the refrigerator (+2...+8°C) | Notes |
|---|---|---|
| Coprogram (general stool analysis) | 8–12 hours | It is advisable to deliver to the laboratory within 4–6 hours. 12 hours possible false results for fatty acids and starch. |
| Analysis for worm eggs and protozoa | 24 hours | For detection ascaris or pinworms it is better to take Giardia within 6 hours. are detected worse after 12 hours of storage. |
| Analysis for occult blood (Gregersen reaction) | 6–8 hours | After 12 hours, the sensitivity of the test drops by 40% Do not store in high humidity (condensation destroys hemoglobin). |
| PCR for infections (rotavirus, norovirus, hepatitis A) | 48 hours | Use special transport media (for example, COPAN UTM) if the storage period exceeds 24 hours. |
| Bacteriological culture (for pathogenic flora) | 2–3 hours | Storage is not recommended. If unavoidable, use preservatives (for example, glycerin buffer solution). |
Critical information: For analysis on calprotectin (marker of intestinal inflammation), feces can be stored for no longer than 5 days at +2...+8°C, but only in a special container with a preservative SarstedtWithout a preservative, the period is reduced to 24 hours.
How to properly collect and store feces: step-by-step instructions
Even if you know the storage time, incorrect sample collection can negate all efforts:
- Preparation:
- 🚿 For 2-3 days, eliminate from your diet foods that color feces (beets, blueberries, activated carbon), as well as fatty foods and alcohol.
- 💊 Stop taking antibiotics, laxatives and iron supplements (if possible, check with doctor).
- 🧼 Wash with warm water and neutral soap (no antiseptics!) before defecation.
- Collection of material:
- 🧻 Use a clean, dry container (pot, vessel) or special a disposable vessel for collecting feces (sold in pharmacies).
- 🚫 Do not take a sample from the toilet - even after disinfection, detergents remain on it.
- 🥄 Take 1-2 teaspoons stool (about 5-10 g) from different parts (top, sides, middle). To test for eggs, worms are needed lumps, not the liquid fraction.
- Packaging and storage:
- 📦 Place the feces in sterile container with spoon (for example, Eppendorf or SarstedtClose the lid). tightly.
- ❄️ Place the container on middle shelf of the refrigerator (not in the door or in the freezer!).
- 📝 Sign the container: full name, date and time of collection, type of analysis.
Clean container with a spoon|Disposable gloves|Paper towel|Pen for signing the container|Memo from the laboratory (if any)-->
If a child is taking the test, use pediatric containers with a narrow neck - they prevent leakage. Suitable for loose stools a container with an absorber (for example, FL Medical).
Which containers are suitable for storing feces (and which ones are not)
Not every container is equally useful. An error in choosing a container can lead to contamination of the sample (ingress of foreign microorganisms) or destruction of the biomaterial.
| Container type | Suitable? | Notes |
|---|---|---|
| Sterile plastic container with spoon (pharmacy) | ✅ Yes | Optimal option. The spoon is built into the lid, which minimizes the risk of contamination. |
| Glass jar (for example, baby food) | ⚠️ Conditionally | Can be used if the jar sterilized (boiling for 10 minutes) is completely dry. The lid must close tightly. |
| Plastic container for food (for example, yogurt) | ❌ No | Even after washing, fats and detergents remain on the walls, which distort results. |
| A container with a preservative (for example, Sarstedt for calprotectin) | ✅ Yes | Required for long-term storage (more than 24 hours) or for specific tests (PCR, bakposev). |
| Bag or plastic bag | ❌ No | Not airtight, there is a high risk of leakage and contact with air, which accelerates decomposition. |
If you use a container with preservative (for example, for analysis on rotavirus or norovirus), make sure that the biomaterial is completely immersed in the solution. Otherwise, part of the sample will dry out and the test will be inaccurate.
⚠️ Attention: Some laboratories provide containers with built-in stabilizer (for example, for a H. pylori antigen test). If you lose such a container, do not replace it with a regular one - the results will be false negative.
What to do if too much time has passed?
There are different situations: you forgot about the analysis, you don’t have time to deliver it to the laboratory, or the refrigerator was suddenly turned off. Here's what you can do:
- ⏳ 12–24 hours have passed (for coprogram or analysis for worm eggs):
If the feces were stored at +2...+8°C in an airtight container, it can still be donated, but warn the laboratory about the shelf life. It may be necessary to retake the analysis.
- ❄️ Fool is frozen (for example, due to a refrigerator malfunction):
Defrosting and re-cooling unacceptable. Such a sample is unsuitable for analysis - you will have to collect it again.
- 🌡️ Stool was stored at room temperature for more than 2 hours:
For most tests (except PCR with a preservative) this means that the results will be unreliable. An exception is the test for enterobiasis (scraping), which can be stored for up to a day at +4°C.
- 🔄 You need to take an analysis, but the storage time has expired:
Some laboratories accept feces from late delivery, but make a note on the form. Please check this point in advance.
Top 5 mistakes that spoil stool analysis
Even if you comply with the shelf life, non-obvious mistakes can distort the results. This is what is most often done incorrectly:
- Collecting feces after an enema or suppositories.
The enema washes out the natural microflora, and the remains of suppositories (for example, glycerin) get into the sample and give a false positive result for fats.
- Storing the container in the door refrigerator.
The temperature there is unstable (from +5 to +15°C), which accelerates the decomposition of enzymes. The shelf is the only correct place.
- Use a matchbox or foil.
Cardboard absorbs moisture, and the foil oxidizes, which affects the pH of the stool. For the analysis of occult blood this is critical.
- Collecting stool after an X-ray with barium.
Barium (contrast agent) makes the sample unsuitable for coprogram within 72 hours after the procedure.
- Delivery of stool to the laboratory in hot weather without a thermal bag.
If it is +25°C or higher outside, and the journey takes more than 30 minutes, use cooling package or thermal container.
What happens if you donate expired feces?
The laboratory can accept the sample, but:
- The coprogram will falsely increase the indicators neutral fat and starch (due to enzymatic breakdown).
- Analysis for worm eggs will show a false negative result, since larvae die during long-term storage.
- The test for occult blood will become uninformative due to the destruction of hemoglobin.
B at best, you will be asked to retake the test, at worst, they will make an incorrect diagnosis.
Frequently asked questions about storing stool
Is it possible to store stool in the freezer if it needs to be taken after 3 days?
No, freezing destroys cells and DNA, which is what the test does uninformative. An exception is special tests (for example, for microbiome), for which the laboratory issues a protocol allowing freezing at −20°C. In other cases, the freezer is unacceptable.
How to store feces if there is no space on the middle shelf in the refrigerator?
Alternatives:
- 🧊 Use thermal bag with cold elements (the temperature inside will be +4°C).
- 🧊 Place the container in bottom drawer for vegetables - there the temperature is more stable than on the door.
- 🧊 If the refrigerator No Frost, you can temporarily place the container in freshness zone (0...+1°C), but no more than 6 hours.
Is it possible to collect feces in the evening, and take it only after 2 days?
Depends on the analysis:
- ✅ PCR for infections — it is possible if you use a container with a transport medium (for example, COPAN UTM).
- ❌ Coprogram or test for occult blood — no, the results will be unreliable.
- ⚠️ Analysis for worm eggs - it is possible, but the sensitivity of the test will drop by 30-50%.
Check with the laboratory whether they accept samples from such a long time ago.
What to do if the stool is liquid and you can’t take it with a spoon?
Use:
- 🥄 A container with an absorber (for example, FL Medical for loose stools).
- 🧻 Pipette (if the stool is very watery) - take 5-10 ml into a sterile test tube.
- 🧴 Urinol (urinal bag)glued to the toilet - this makes it easier to collect the liquid mass.
Do not use cotton swabs or napkins - fibers get into the sample and interfere with the analysis.
Do you need to submit stool to the laboratory in the original container, or can it be transferred?
It is better to submit it in the original container, especially if:
- B it contains preservative (for example, for PCR).
- The laboratory issued special container (with a barcode or label).
If you have to transfer:
- Use a new sterile container.
- Transfer the feces clean spoon (not with your hands!).
- Sign the new container with the same data.