Blood, pH & Specific Gravity in Urine: What BLO, pH and SG Mean on a Urine Test Strip
Dr Pramod kumar
What Do BLO, pH and SG Mean on a Urine Test Strip?
On a multi-parameter urine reagent strip:
- BLO = Blood
- pH = Relative acidity or alkalinity of urine
- SG = Specific Gravity
These three parameters provide different types of urine chemistry information.
BLO screens for blood-related reactions, pH indicates whether the specimen is relatively acidic or alkaline, and SG provides an estimate of urine concentration.
They are commonly included in broader multi-parameter urinalysis strips such as Microsidd URS10T and Mission 10U.
For an overview of all common urinalysis parameters, read our 10 Urine Test Strip Parameters Explained.
1. BLO – Blood in Urine
BLO refers to the blood reagent area on a urine test strip.
Depending on the product chemistry, this reagent pad can respond to the peroxidase-like activity associated with:
- Intact red blood cells
- Hemoglobin
- Myoglobin
This means a positive BLO reagent result does not by itself tell you exactly which of these is responsible.
What Does Blood in Urine Mean?
Blood-related reactions in urine may occur for many reasons.
Possible explanations can include:
- Urinary tract inflammation or infection
- Urinary stones
- Menstrual contamination
- Strenuous exercise
- Trauma
- Other urinary or systemic conditions
A positive blood pad does not identify the cause.
Unexpected or persistent findings should be interpreted together with symptoms, specimen quality, microscopy and other clinical information where appropriate.
Does Positive BLO Mean Visible Blood Must Be Present?
No.
A reagent strip may detect a blood-related reaction even when the urine does not visibly appear red or pink.
This is one reason urine dipsticks can be useful as screening tools.
Can a Positive BLO Result Diagnose a UTI?
No.
Blood may occur during urinary tract infection, but it has many other possible causes.
For urinary tract screening, parameters such as leukocytes and nitrite are generally more directly relevant.
Read our Leukocytes & Nitrite in Urine: LEU + NIT UTI Screening Guide →
Blood on Dipstick vs Red Blood Cells Under Microscopy
| Urine Dipstick BLO | Urine Microscopy |
|---|---|
| Screens for blood-related chemical reaction | Can directly identify red blood cells in the sediment |
| May respond to hemoglobin or myoglobin | Shows formed cellular elements |
| Rapid screening method | Requires microscopic examination |
| Does not determine the exact cause | Can provide additional morphological information |
The two methods provide different information and may be used together where clinically appropriate.
Can Exercise Affect the BLO Result?
Strenuous exercise can sometimes be associated with temporary blood-related findings in urine.
If the result is unexpected, repeat testing or additional assessment may be appropriate depending on the circumstances.
Can Menstrual Contamination Affect BLO?
Yes.
Blood from menstruation or other external contamination can potentially cause a positive blood reagent-pad result.
Appropriate specimen collection is therefore important when interpreting an unexpected positive BLO result.
2. What Does Urine pH Mean?
Urine pH indicates whether a urine specimen is relatively acidic or alkaline.
The pH scale ranges from acidic at lower values to alkaline at higher values.
Urine pH varies naturally and should not be interpreted as a disease-specific marker by itself.
What Can Affect Urine pH?
Urine pH may be influenced by factors such as:
- Diet
- Metabolism
- Medications
- Hydration
- Timing of specimen collection
- Urinary bacteria
- Specimen storage
- Other physiological or clinical factors
What Does Acidic Urine Mean?
An acidic urine result simply means the measured pH is on the acidic side of the product's scale.
Urine may become relatively acidic under different physiological or dietary circumstances.
An acidic pH alone does not diagnose a medical condition.
What Does Alkaline Urine Mean?
An alkaline result means the urine pH is toward the alkaline side of the scale.
Urine can become more alkaline because of diet, medication, bacterial activity or specimen changes after collection.
Interpretation should therefore consider the broader context.
Why Can an Old Urine Sample Become More Alkaline?
Urine can change after collection.
If a specimen is left standing for an extended period, bacterial growth and chemical changes may alter its pH.
This is one reason fresh urine is generally preferred for routine reagent-strip testing unless a specific laboratory protocol states otherwise.
Can Urine pH Diagnose a UTI?
No.
Some urinary bacteria can influence urine pH, but pH by itself does not diagnose infection.
LEU, NIT, symptoms, microscopy and culture may provide more relevant information in suspected UTI.
Can Urine pH Tell You Your Blood pH?
No.
Urine pH and blood pH are different measurements.
The body's blood acid-base balance is tightly regulated, while urine pH can vary much more widely as the kidneys excrete acids and bases.
A urine pH strip should therefore not be used as a substitute for blood acid-base testing.
3. SG – Specific Gravity in Urine
SG stands for specific gravity.
Urine specific gravity provides an estimate of how concentrated or dilute a urine specimen is relative to water.
A more concentrated specimen generally has a higher specific gravity, while a more dilute specimen generally has a lower specific gravity.
What Does High Urine Specific Gravity Mean?
A relatively high SG indicates a more concentrated urine specimen.
This may occur in circumstances such as:
- Reduced fluid intake
- Fluid loss
- Concentrated morning urine
- Presence of dissolved substances in urine
- Other physiological or clinical circumstances
A high strip result does not identify the cause by itself.
What Does Low Urine Specific Gravity Mean?
A relatively low SG indicates a more dilute urine specimen.
This may be influenced by:
- Higher fluid intake
- Timing of specimen collection
- Urine-concentrating ability
- Medication
- Other physiological factors
Again, SG alone should not be used as a standalone diagnosis.
Does Urine Specific Gravity Measure Hydration?
Specific gravity can provide useful information about urine concentration and may contribute to assessment of hydration status.
However, hydration is only one of several factors that can affect urine concentration.
SG should therefore not be treated as a precise standalone hydration test.
Does SG Measure Kidney Function?
No.
Specific gravity can contribute information about the urine's concentration, but it does not directly measure overall kidney filtration function.
Kidney assessment may require additional tests such as blood creatinine, estimated glomerular filtration rate, urine albumin measurements and other investigations depending on the clinical question.
Urine Strip SG vs Refractometer
Urine specific gravity may be estimated using a reagent strip or measured using instruments such as a refractometer.
| Reagent Strip SG | Refractometer |
|---|---|
| Rapid strip-based estimate | Instrument-based measurement |
| Part of multi-parameter urinalysis | Dedicated physical measurement |
| Primarily responds to ionic concentration according to strip chemistry | Responds to total dissolved-solute effect on refractive index |
| Convenient for routine screening | Often used where more detailed SG assessment is required |
The methods are not chemically identical and results may not always match exactly.
How BLO, pH and SG Work Together
These three parameters provide different pieces of information:
| Parameter | Main Screening Information |
|---|---|
| BLO | Blood-related reaction |
| pH | Relative urine acidity / alkalinity |
| SG | Relative urine concentration |
They should not be interpreted as a single diagnostic panel.
Instead, each contributes context to a broader urinalysis result.
Why a 10-Parameter Strip Is Useful for BLO, pH and SG
Focused 2-parameter strips such as glucose + protein or glucose + ketone do not normally include BLO, pH and SG.
When broader urine chemistry screening is required, a multi-parameter strip provides these parameters together with other markers.
Microsidd URS10T
Microsidd URS10T includes:
- Leukocytes
- Nitrite
- Urobilinogen
- Protein
- pH
- Blood
- Specific Gravity
- Ketones
- Bilirubin
- Glucose
View Microsidd URS10T 10-Parameter Urine Test Strips →
Mission 10U
Microsidd also supplies Mission 10U Urinalysis Reagent Strips for broad multi-parameter urine chemistry screening.
How to Test BLO, pH and SG with a Urine Strip
The exact procedure varies by product, so always follow the Instructions for Use supplied with the specific reagent strips.
A typical workflow includes:
- Collect a fresh urine specimen in a clean, suitable container.
- Check the strip expiry date and condition.
- Remove one strip without touching the reagent pads.
- Close the strip container immediately.
- Immerse the required reagent areas according to the product instructions.
- Remove the strip after the specified immersion time.
- Remove excess urine as directed.
- Start timing immediately.
- Compare BLO, pH and SG with their respective colour scales at the specified times.
- Record results where required.
- Dispose of the used strip appropriately.
For detailed technique guidance, read:
How to Read Urine Test Strips Correctly: Colour Chart, Timing & Common Errors →
Use a Suitable Urine Specimen Container
Reliable testing begins with appropriate specimen collection.
Contamination, detergent residues or unsuitable containers may interfere with urinalysis.
View Urine Specimen Container →
Why Reading Times Matter
BLO, pH and SG reagent chemistries may develop at different rates.
Do not assume that all pads should be interpreted at the same time.
Reading too early or too late can affect visual interpretation.
Always use the parameter-specific reading times shown on the product chart or IFU.
Why the Correct Colour Chart Matters
Each reagent-strip system has its own colour ranges and chemistry.
Do not use:
- A colour chart from another brand
- A chart from a different strip configuration
- A generic online chart
- A faded or damaged reference scale
Use only the chart supplied with the exact urine reagent strips being tested.
What Can Cause Misleading BLO Results?
Potential influences vary by product but may include:
- Menstrual contamination
- Oxidizing contaminants
- Improper specimen collection
- Expired strips
- Incorrect storage
- Incorrect reading time
- Product-specific chemical interferences
Always consult the product IFU for exact limitations.
What Can Cause Misleading pH Results?
Potential influences can include:
- Old urine specimens
- Bacterial growth after collection
- Improper storage
- Contaminants
- Incorrect reading time
What Can Affect SG Results?
Specific gravity interpretation can be affected by:
- Hydration
- Urine solute concentration
- Specimen pH
- Product-specific reagent chemistry
- Testing technique
- Method used to measure SG
Visual Reading vs Analyzer Reading
Many multi-parameter urine strips are designed for visual interpretation, while compatible professional reagent strips may also be read using urine chemistry analyzers.
| Visual Reading | Analyzer Reading |
|---|---|
| Operator compares reagent colours | Optical system measures reflectance |
| Useful for lower-volume testing | Useful for repeated professional workflows |
| Manual recording | May support result storage and printing |
| Lighting and operator perception may influence interpretation | Helps standardize compatible strip reading |
Professional analyzer options from Microsidd include:
Always verify exact reagent-strip compatibility before analyzer use.
When Should an Abnormal BLO, pH or SG Result Be Followed Up?
Further assessment may be appropriate when:
- Blood remains positive on repeat testing
- Urinary symptoms are present
- Visible blood is present
- Results are unexpected
- Several urine parameters are abnormal together
- A healthcare professional recommends repeat or confirmatory testing
The appropriate follow-up depends on the finding and clinical circumstances.
Explore the Microsidd Urine Chemistry Range
Microsidd's Urine Chemistry collection includes focused urine reagent strips, 10-parameter urinalysis strips, analyzers, specimen containers and accessories.
Explore the Complete Urine Chemistry Collection →
Continue Learning About Urinalysis
- Urinalysis & Urine Test Strips Complete Guide
- 10 Urine Test Strip Parameters Explained
- How to Read Urine Test Strips Correctly
- Leukocytes & Nitrite in Urine
- Urine Glucose Test Strips Complete Guide
- Protein in Urine Test Strips Complete Guide
- Ketones in Urine Test Strips Complete Guide
Frequently Asked Questions
What does BLO mean on a urine test strip?
BLO stands for blood. The reagent area screens for blood-related reactions in the urine specimen.
Does positive BLO always mean red blood cells are present?
No. Depending on the reagent system, the pad may also respond to hemoglobin or myoglobin.
Does blood in urine mean UTI?
Not necessarily. Blood can occur for many reasons and should not automatically be attributed to infection.
Can exercise cause a positive blood result?
Strenuous exercise can sometimes be associated with temporary blood-related findings in urine.
Can menstruation affect a urine blood strip?
Yes. Menstrual contamination can potentially produce a positive BLO result.
What does urine pH mean?
Urine pH indicates whether the urine specimen is relatively acidic or alkaline.
Does alkaline urine mean infection?
No. Urine pH can be influenced by many factors. pH alone does not diagnose a urinary infection.
Can urine pH tell me my blood pH?
No. Urine pH and blood pH are different measurements.
What does SG mean?
SG stands for specific gravity and provides an estimate of urine concentration.
Does high SG mean dehydration?
A higher SG can occur with concentrated urine and may be influenced by hydration, but dehydration cannot be diagnosed from SG alone.
Does low SG mean kidney disease?
No. A low result can occur for several reasons and does not diagnose kidney disease by itself.
Which urine strip tests BLO, pH and SG together?
Microsidd URS10T includes all three parameters as part of its 10-parameter profile.
Does Mission 10U include blood, pH and specific gravity?
Yes. Mission 10U includes BLO, pH and SG among its multi-parameter tests.
Can I use GLU + PRO or GLU + KET strips to test these parameters?
No. Focused 2-parameter strips do not include the full BLO + pH + SG combination.
Can the same urine strip be reused?
No. Urine reagent strips are intended for single use.
Medical Information Notice
This article is provided for general educational and product-selection information and is not a substitute for medical advice, diagnosis or treatment.
Blood, pH and specific gravity reagent-strip results are screening findings. An abnormal result does not by itself identify the underlying medical cause.
Results may be influenced by specimen collection, contamination, timing, hydration, exercise, medication, storage conditions and other physiological or clinical factors.
Persistent, unexpected or clinically significant abnormalities should be evaluated by an appropriately qualified healthcare professional and confirmed with additional laboratory or clinical investigations where necessary.
Do not begin, stop or modify medication or other medical treatment solely on the basis of a urine reagent-strip result.
Always follow the Instructions for Use supplied with the exact urine reagent strip being used.