Urine tests are commonly used to check for a variety of health conditions. The components of urine can provide important information about your health and help identify potential issues. However, many different factors can affect the results of urine tests. Being aware of what might influence your results can help ensure the accuracy of this simple diagnostic tool.
Medications
Many different prescription and over-the-counter medications can impact urine test results. Medications are filtered through the kidneys and can directly interact with the compounds being measured in a urine test. Some examples of medications that may affect test results include:
- Antibiotics like amoxicillin and ciprofloxacin, which can cause a false positive result for proteins or red blood cells
- Diuretics like furosemide, which increase urination and dilute urine
- Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs), which may cause a false positive result for blood
- Vitamin C supplements, which can turn urine more acidic and affect the detection of certain compounds
Always inform the personnel administering your urine test about all medications you are currently taking. They can then take this information into account when interpreting your test results.
Diet and Nutritional Supplements
What you eat and drink can significantly influence your urine composition and test findings. For example:
- Eating beets can turn urine pink or reddish, mimicking blood in the urine
- Taking B vitamin supplements can make urine bright yellow, resembling signs of liver or kidney problems
- Consuming a lot of protein from meat or supplements can cause high protein readings
- Caffeine and alcohol increase urination and affect concentration
For best accuracy, limit consumption of colored foods and supplements for 24-48 hours before a urine test. Drink normal amounts of fluids and avoid over-hydrating which can dilute results.
Medical Conditions
Certain medical conditions that affect kidney function, metabolite levels, or overall health can impact urine test findings. For instance:
- Kidney disease affects the kidneys’ ability to filter waste products and reabsorb electrolytes and nutrients.
- Diabetes can cause excess protein and sugar to spill into the urine with hyperglycemia.
- Urinary tract infections (UTIs) introduce bacteria, white blood cells, and proteins.
- Dehydration concentrates urine contents, while overhydration dilutes it.
Always inform the testing provider of any underlying medical conditions, as they may warrant different reference ranges for interpreting your lab work.
Contaminants
Blood, protein, or other compounds in your urine could be due to contamination rather than a health issue. Potential sources of contaminants include:
- Menstruation – Blood from your period can tint urine red.
- Vaginal discharge – Vaginal secretions can introduce proteins.
- Stool – Fecal matter from poor wiping can contaminate the urine sample.
- Bacterial contamination – Bacteria around the genitals or hands can get into the sample.
Use proper technique when collecting urine to avoid contamination. Women should not collect samples when actively menstruating. Let the provider know if contamination is a possibility so your results can be interpreted appropriately.
Collection and Storage Errors
How you collect and store the urine sample can introduce substantial errors. Problems may arise if:
- The sample sits unrefrigerated for too long before testing.
- You use an unclean collection cup or accidental touch the inside of the container.
- Too little urine is provided for the necessary tests.
- The first morning urine or random sample is not the optimal type needed.
- You contaminate the sample by not properly washing hands beforehand.
Follow collection instructions carefully for best results. Let the testing facility know of any potential issues with how you collected or stored the specimen.
Normal Variations
Urine contents can vary normally throughout the day and across seasons. For example:
- First morning urine is more concentrated while urine later in the day is more dilute.
- Eating a heavy meal can cause temporary protein and sugar spikes.
- You tend to urinate more in summer, diluting solutes.
- Strenuous exercise can break down muscle and cause proteinuria.
Understand that one-off results may reflect temporary variations. Serial testing may be needed if unusual findings require further monitoring.
Lab Errors
While uncommon with standard precautions, lab mistakes can generate inaccurate test results. Potential errors include:
- Mislabeled samples resulting in mixed-up results.
- Testing inaccuracies from equipment calibration issues.
- Clerical errors in reporting or entering results into records.
- Failure to account for interfering medications, medical conditions or other factors.
- Use of incorrect normal reference ranges for the patient.
Ask for a retest or second opinion if serious concerns arise about the accuracy of your urine testing results.
When to Retest
With so many variables at play, one-time urine testing may not offer definitive answers about your health. Repeat testing should be considered if:
- Results fall slightly outside the normal range and need rechecking.
- Findings are abnormal but you have no concerning symptoms.
- Results don’t align with your medical history and other test results.
- Unusual findings could have been temporary based on diet, medications or collection issues.
- Confirmation is needed to decide on a diagnosis or treatment plan.
Follow up abnormal or questionable results with repeat testing. Make sure proper protocol is followed for the most accurate findings.
Conclusion
Many factors can affect the composition of urine and results of urine testing. Being aware of potential influences can help you properly interpret your results. Abnormal findings may warrant repeat testing under optimal conditions. Make sure your healthcare provider knows your medications, supplements, diet, and medical history to contextualize urine screening results.