A general urinalysis (UU) is a standard procedure when diagnosing diseases, preventive examinations or preparing for surgery. However, it is not always possible to deliver biomaterial to the laboratory immediately after collection. In such cases, the question arises: can urine be stored in the refrigerator and how long will it remain suitable for research?
The answer depends on several factors: storage temperature, type of container, time of day when the urine was collected, and even on the purpose of the analysis. Doctors and laboratory technicians warn: improper storage can lead to false results the appearance of bacteria, changes in acidity or cell destruction. In this article, we will look at how to store urine for OAM in the refrigerator without risking the accuracy of diagnosis, as well as what mistakes patients most often make.
Why does urine sometimes need to be stored before analysis?
The ideal scenario is to deliver urine to the laboratory within 1–2 hours after collection. But in practice this is not always possible. Here are the situations when storage is required:
- 🕒 Morning collection, but the laboratory opens later (for example, urine is collected at 6:00, and the reception of biomaterial begins at 8:30).
- 🏥 Referral for analysis is issued in the evening, and the morning portion of urine is more informative for diagnosis.
- 🚗 Long journey to the laboratory (for example, in rural areas or during traffic jams in the city).
- 👶 Urine collection from infantswhen the process can take several hours.
In these cases, the refrigerator becomes temporary storage. However, it is important to understand: even at low temperatures, processes begin in the urine that can distort the results. For example, at room temperature, after 1 hour, bacteria multiply in it, and at +4°C this process slows down, but does not stop.
Once a year (prevention)|Only as prescribed by a doctor|More than 2 times a year|Never donated-->
Permissible periods for storing urine in the refrigerator
According to clinical recommendations the maximum shelf life of urine for general analysis in the refrigerator is 24 hours at a temperature of +2...+8°C. However, this extreme limit, and the sooner the biomaterial is delivered to the laboratory, the more accurate the results will be. Let's take a closer look:
| Storage temperature | Maximum period | What happens to urine | Risk of analysis distortion |
|---|---|---|---|
| +2...+4°C (bottom shelf of the refrigerator) | up to 24 hours | The growth of bacteria slows down, but pH changes and cell destruction are possible | Low (subject to collection rules) |
| +4...+8°C (refrigerator door) | up to 12 hours | Moderate growth of microorganisms, false positive results for infections are possible | Medium |
| Room temperature (+18...+25°C) | up to 2 hours | Rapid proliferation of bacteria, change in color and odor, destruction of formed elements | High |
| Freezer compartment (below 0°C) | Storage is prohibited! | Crystallization of salts, destruction of cells, complete unsuitability for analysis | 100% distortion |
Important: if urine was stored for more than 2 hours at room temperature, its not allowed place in the refrigerator and submit for analysis. In this case, it is necessary to collect a new portion.
⚠️ Attention! Some laboratories establish their own rules for receiving biomaterial. For example, private clinics may refuse to accept urine that has been stored for more than 4–6 hours, even in the refrigerator. Check the requirements in advance.
How to properly store urine in the refrigerator: step-by-step instructions
To minimize the risk of distorted results, follow these rules:
Collect urine in a sterile container (pharmacy or laboratory)|Close tightly lid to prevent air from entering| Label the container (full name, date and time of collection)| Place the container on the bottom shelf of the refrigerator (coldest zone)| Do not place next to foods with a strong odor (fish, onions, spices)-->
Additional nuances:
- 🧊 Temperature: optimal -
+2…+4°C. Measure it with a thermometer if the refrigerator is not equipped with a display. - 🕒 Collection time: for OAM it is preferable morning portion (the first one after sleep). If collected in the evening, store no longer than 12 hours.
- 🧴 Container: use only sterile containers from a pharmacy or laboratory. Homemade jars (even washed) may contain microorganisms.
- 🚫 Freezing: strictly prohibited! When thawing, urine becomes cloudy, and cells and salts are destroyed.
If the urine was collected catheter or child using a urinal, the shelf life is reduced to 4-6 hours even in the refrigerator due to more high risk of bacterial contamination.
What happens to urine if stored improperly?
Even a short-term violation of storage conditions can lead to the following changes:
- 🦠 Bacteriuria: false detection of bacteria (for example, E. coli), which in fact no.
- 🔬 Change in pH: urine becomes more alkaline, which masks renal pathology.
- 🩸 Hemolysis: destruction of red blood cells, which is why the analysis will not show microhematuria.
- 🌫️ Closure: precipitation of salts (phosphates, urates), which are mistakenly mistaken for infection.
- 🧪 False increase in glucose: due to the breakdown of cells, “sugar” may appear that is not actually there.
For example, if urine was stored at room temperature for 3 hours, ammonia smell may appear in it - this is a sign of decomposition of urea by bacteria. The laboratory technician will write down on the form: “The smell of ammonia,” which the doctor can interpret as a urinary tract infection.
An example of a distorted analysis
Suppose the patient stored urine for 12 hours in the refrigerator on the door (+6°C). In the results of OAM, the following may appear:
- Leukocytes: 10–15 in the visual field (norm up to 5) - false inflammation.
- Bacteria: "+" or "++" - although there is no infection.
- Epithelium: a large number - due to destruction cells.
The doctor may mistakenly prescribe antibiotics or additional examinations.
Frequent errors when storing urine
Even experienced patients sometimes make mistakes that nullify all efforts. Here are the most common:
- Storage in the freezer. After thawing, urine becomes unsuitable for microscopy.
- Use of non-sterile containers. Baby food or mayonnaise jars contain residual fat and microbes.
- Long-term storage on the refrigerator door. The temperature here is higher than on the lower shelves.
- Pouring urine from one container to another. This increases the risk of contamination.
- Storage near food. For example, next to cheese or sausage, urine can absorb foreign odors.
Another typical mistake is collect urine in the evening for morning delivery. Many people think that this is more convenient, but in 10–12 hours bacteria have time to multiply in it, even in the refrigerator. If the laboratory only takes tests in the morning, it is better to get up early and collect a fresh portion.
⚠️ Attention! If you are taking medications (for example, antibiotics, diuretics, or vitamins), tell your doctor. Some drugs change the composition of urine within 2-3 hours after administration, and even proper storage will not save you from false results.
Special cases: urine in children, pregnant women and during specific tests
For some categories of patients, the rules for storing urine are different:
- 👶 Infants and children under 3 years of age: urine collected using a urine bag is stored no longer 4 hours (even in the refrigerator). The reason is the high risk of contamination by skin microflora.
- 🤰 Pregnant women: due to the increased risk of urinary tract infections, it is advisable to deliver urine to the laboratory within 1–1.5 hours. If this is not possible, store no more than 6 hours at +4°C.
- 🩺 Analysis according to Nechiporenko or Zimnitsky: for these studies, urine is stored no longer 1.5–2 hours at room temperature. Storage in the refrigerator is allowed only in exceptional cases (maximum 4 hours).
- 💉 Analysis for steroids or hormones: some metabolites (for example, cortisol) are destroyed even at +4°C. Check with the laboratory whether special preservatives are needed.
To collect urine from children, use sterile urinals with an adhesive base (for example, Pee-Pee Collector). They minimize the risk of bacteria entering the skin. After collection, immediately pour the urine into a sterile container and store for no longer than 2 hours.
What to do if urine has been stored for too long?
If for some reason the urine has been stored longer than the permissible period, do not try to “save” the situation, for example, by diluting it with water or adding preservatives yourself. Here's what experts recommend:
- Collect a new portion. This is the only reliable way to get accurate results.
- Inform the doctor about the storage violation. He may reschedule the test or prescribe an alternative examination (for example, a blood test).
- Do not submit “suspicious” urine. False results can lead to incorrect diagnosis and unnecessary treatment.
An exception is cases when the laboratory uses special stabilizing solutions (for example, for daily urine analysis). In this case, urine can be stored for up to 48 hours, but only in laboratory conditions.
If you doubt whether urine is suitable for analysis, pay attention to its appearance:
- 🟢 Normal: light yellow, transparent, without sediment or pungent odor.
- 🟡 Suspicious: cloudy, with flakes, ammonia smell - even if stored in the refrigerator.
- 🔴 Unsuitable: with visible sediment, discolored (pink, green), putrid odor.
FAQ: Frequently asked questions about storing urine
Can urine be stored in the refrigerator in a regular jar?
No. Homemade jars are not sterile, even if washed with baking soda or boiling water. For analysis, use only pharmacy containers with a tight lid. They are made of chemically neutral materials and are sterilized.
How long can urine be stored for sugar analysis?
For glucose (sugar) analysis, urine is stored no longer 4-6 hours at +4°C. If stored for a longer period of time, the glucose is destroyed and the result will be false negative. If you need to store longer, use special preservatives (for example, sodium fluoride).
Can urine be transported in a refrigerated bag?
Yes, but only if the bag maintains the temperature +2…+8°C and transportation takes no more than 1-2 hours. For long trips (for example, to another city), use thermal containers with cold cells. Check with the laboratory whether they accept biomaterial after such transportation.
What happens if urine frozen in the refrigerator?
Frozen urine completely loses diagnostic value. When thawed:
- Cells (erythrocytes, leukocytes) are destroyed.
- Salts precipitate, which distorts the data on the crystals.
- Protein and glucose can give false positive or false negative results.
This test will have to be retaken.
Is it possible to store urine for bacterial culture in the refrigerator?
No For bacteriological culture, urine must be delivered to the refrigerator. laboratory within 1-2 hours without storage. The refrigerator distorts the number and species composition of microorganisms. If it is impossible to immediately deliver urine, use transport media (for example, Uricult).