A Patient’s Guide to Collecting Blood, Urine, and Stool Samples

Laboratory testing does not end when a test is ordered. The quality of the specimen itself can influence whether the laboratory is able to process the sample and how useful the result may be.

Blood, urine, and stool specimens each have different collection requirements. Some are collected by healthcare professionals, while others can be completed at home using a laboratory kit.

The most important rule is simple:

Follow the instructions provided with your specific laboratory test.

Different tests may require different collection times, containers, preservatives, storage temperatures, fasting conditions, or shipping schedules. An instruction that is correct for one test may be wrong for another.

This guide explains the general principles of collecting blood, urine, and stool specimens, common mistakes to avoid, and what to do when a collection does not go according to plan.

If you are new to advanced testing, you may want to begin with What Is Specialty Laboratory Testing? A Patient’s Guide. You can also explore our full Specialty Laboratory Testing Resource Center.

Why Does Sample Collection Matter?

A laboratory can only analyze the specimen it receives.

If the specimen was collected at the wrong time, contaminated, stored incorrectly, incompletely collected, or shipped outside the laboratory's requirements, the result may be less useful or the laboratory may need a new sample.

This is sometimes called a pre-analytical issue because the problem occurs before the laboratory actually analyzes the specimen.

Important variables can include:

• Collection time

• Fasting status

• Hydration

• Medications and supplements

• The collection container used

• The amount of specimen collected

• Contamination from urine, water, skin, or other material

• Storage temperature

• Time between collection and laboratory processing

• Shipping conditions

Specialty laboratory testing can be especially sensitive to these variables because some panels require multiple specimens, timed collections, preservatives, freezing, refrigeration, or collection on particular days.

Before you collect anything, read the entire set of instructions.

Before Collecting Any Laboratory Sample

Do not wait until you are already holding a specimen container to figure out what you are supposed to do.

Review your kit first.

Confirm which specimens you need to collect and whether you have all of the required containers, tubes, collection cards, labels, applicators, preservative vials, shipping materials, and laboratory forms.

Also confirm:

• Whether you need to fast

• Whether medications should be taken normally

• Whether supplements need special consideration

• Whether the specimen must be collected in the morning

• Whether multiple collections are required

• Whether a urine collection is a single specimen or timed collection

• Whether a stool specimen needs to be refrigerated or frozen

• Whether a blood sample requires a professional blood draw

• Whether collection can occur on a weekend

• How quickly the specimen must be shipped

• Whether you must schedule a pickup in advance

For blood-testing preparation specifically, see How to Prepare for Your Laboratory Appointment.

Do not stop prescription medications simply because you are collecting a laboratory specimen unless your physician has specifically instructed you to do so.

How Are Blood Samples Collected?

Blood specimens can be collected in several ways.

The two methods patients are most likely to encounter are a conventional venous blood draw and an at-home fingerstick or dried-blood-spot collection.

Conventional Blood Draw

Most routine blood testing and many specialty laboratory panels require venous blood.

This is usually performed by a trained phlebotomist at a laboratory, medical office, hospital, mobile phlebotomy service, or another appropriate collection site.

During a typical blood draw, the phlebotomist places a tourniquet around your arm, cleans the skin, inserts a sterile needle into a vein, and fills one or more collection tubes.

Different tubes may contain different additives or may need to be handled differently after collection. For that reason, venous blood collection should generally be left to properly trained personnel.

Your responsibility is mainly to arrive properly prepared.

That may mean following instructions about:

• Fasting

• Hydration

• Medication timing

• Supplement use

• Exercise

• Alcohol

• Time of day

• Timing relative to hormone treatment or medication doses

MedlinePlus notes that some laboratory tests require fasting while many do not, which is why preparation should be based on the specific tests ordered rather than a universal rule.

If you have a history of becoming dizzy or fainting during blood draws, tell the phlebotomist beforehand.

What Is a Dried Blood Spot or Fingerstick Collection?

Some specialty laboratories use small amounts of capillary blood obtained from a fingertip.

Instead of filling a standard blood tube, you may be asked to place blood onto a collection card or into a small collection device.

These kits are often designed for home use.

Although the process appears simple, the laboratory still needs an adequate specimen.

Before beginning:

Wash and dry your hands according to the kit instructions. Make sure the collection card or device is ready before using the lancet.

Some kits recommend warming the hands first because this may improve blood flow.

Use the lancet exactly as directed and allow the blood to enter the collection area specified by the laboratory.

Avoid touching the collection surface with your fingers.

If the kit uses a dried blood spot card, allow it to dry for the amount of time specified before packaging it. Do not place a wet collection card into its shipping envelope unless the instructions specifically direct you to do so.

Do not assume that you should repeatedly add blood to a partially dried spot. Different collection cards have different requirements.

The instructions supplied by the laboratory take priority over generic fingerstick advice.

If you cannot obtain enough blood, contact the laboratory rather than improvising a collection technique that may make the specimen unusable.

How Do You Collect a Urine Sample?

Urine testing can range from a simple single specimen to a carefully timed collection lasting many hours.

That means there is no single correct method for every urine test.

Common collection types include:

• Random urine specimens

• Clean-catch urine specimens

• First-morning urine

• Timed urine collections

• 24-hour urine collections

• Multiple urine samples collected at different times of day

• Specialty urine collections for hormones, metabolites, nutrients, environmental exposures, or other biomarkers

Always determine which type you have been asked to collect before beginning.

How to Collect a Clean-Catch Urine Sample

A clean-catch or midstream urine specimen is commonly used when the goal is to reduce contamination from skin or genital bacteria.

When a clean-catch sample has specifically been requested, you will typically be given cleansing materials and a sterile collection cup.

The general process involves cleaning the genital area as directed, beginning to urinate into the toilet, then moving the collection cup into the urine stream without touching the inside of the cup or lid.

After enough urine has been collected, you finish urinating into the toilet and close the container securely.

MedlinePlus specifically notes that proper clean-catch technique helps reduce contamination from germs on the skin.

However, do not automatically use midstream clean-catch technique for every specialty urine test.

Some specialty panels intentionally require the first urine of the morning, the entire void, or urine collected during particular time windows.

Follow the instructions for the test you were given.

What Is a First-Morning Urine Sample?

Some tests request the first urine after waking.

This type of sample may provide a more standardized collection because the urine has accumulated in the bladder overnight.

If your instructions specify first-morning urine, collect it when you first wake unless the laboratory defines the timing differently.

Do not substitute an afternoon specimen simply because it is more convenient without first checking whether timing matters.

What Is a Timed or 24-Hour Urine Collection?

Some laboratory tests measure substances excreted over a period of time rather than in a single urine sample.

You may therefore receive a large collection container and instructions to collect urine during a defined period.

The accuracy of a timed urine collection depends heavily on collecting the specimens during the required interval.

If you accidentally miss a collection, spill urine, start at the wrong time, or forget part of the collection, contact the laboratory or your healthcare professional before submitting the container.

Do not simply continue and assume the missing specimen does not matter.

Some timed collections also need refrigeration or another specific storage condition during the collection period.

Use the storage instructions supplied with your test.

Common Urine Collection Mistakes

Urine collection problems often happen because the patient assumes every urine test is performed the same way.

Avoid:

• Collecting at the wrong time of day

• Using a household container instead of the supplied container

• Touching the inside of a sterile collection cup

• Failing to complete an entire timed collection

• Discarding a preservative from the collection container

• Adding anything to the specimen that was not specifically instructed

• Refrigerating a sample that should remain at room temperature

• Leaving a specimen unrefrigerated when refrigeration is required

• Sending an unlabeled container

If you are uncertain, contact the laboratory before altering, discarding, refrigerating, freezing, or shipping the sample.

How Do You Collect a Stool Sample?

Stool testing is commonly used for gastrointestinal evaluations and may assess pathogens, inflammation, digestion-related markers, blood, or other selected measurements.

Specialty gastrointestinal panels may evaluate additional markers, which you can learn about in Specialty Testing for Gastrointestinal Health: Stool, Microbiome, and Digestive Markers.

The basic principle of stool collection is to obtain the requested stool without contaminating it with toilet water, urine, cleaning products, or other material.

The CDC recommends collecting stool into a clean, dry, leakproof container and preventing urine, water, soil, or other materials from contaminating the specimen.

Your kit may contain a collection tray, paper collection device, plastic collection device, or another method for catching the bowel movement before it enters the toilet water.

Follow that method rather than attempting to retrieve a specimen directly from toilet water.

Transferring Stool Into Collection Containers

Specialty stool kits may contain several different containers.

Some may be empty.

Others may already contain a liquid preservative.

Do not pour out a liquid simply because you assume the container should be empty.

The preservative may be an intentional and necessary part of the testing process.

Your kit may instruct you to use a small scoop or applicator attached to the lid to transfer a particular amount of stool into the vial.

Some tests request sampling from more than one area of the bowel movement.

Others require only a very small amount.

More stool is not necessarily better.

If the vial has a fill line, follow it.

Overfilling a container can interfere with the laboratory's required specimen-to-preservative ratio or make the container difficult to seal.

MedlinePlus patient instructions for stool testing similarly emphasize collecting the specimen in a clean, dry manner, preventing contamination with urine or toilet water, sealing the container, and labeling or returning it as directed.

What If Your Stool Sample Touches Urine or Toilet Water?

If the specimen becomes contaminated, do not automatically submit it.

Urine and toilet water can alter the specimen or introduce material that was not intended to be analyzed.

The safest approach is usually to contact the laboratory and ask whether you should repeat the collection.

If you still have enough supplies to recollect properly, the laboratory may recommend doing so.

How Should Laboratory Samples Be Labeled?

Follow the labeling instructions that came with your kit.

Depending on the laboratory, you may need to record:

• Your name

• Date of birth

• Date of collection

• Exact collection time

• Specimen number

• Collection day

• Other identifying information

Some laboratories provide preprinted labels.

Others require you to complete the labels yourself.

Do not assume the laboratory will be able to identify an unlabeled tube from the shipping box alone.

Labeling is part of specimen collection.

Should Samples Be Refrigerated or Frozen?

There is no universal answer.

Some specimens must remain at room temperature.

Some require refrigeration.

Some need to be frozen completely before shipping.

Others contain preservatives specifically designed to keep them stable without refrigeration.

Never assume that colder is automatically better.

Freezing a specimen that should not be frozen can be just as problematic as leaving a specimen warm when it should have remained cold.

Use the exact storage instructions supplied by the laboratory.

If you cannot find them, contact the laboratory before storing the specimen.

When Should You Ship Your Samples?

Shipping requirements can be just as important as collection requirements.

Some specialty laboratories discourage shipping late in the week because a temperature-sensitive package could remain with the carrier over a weekend.

Other kits are specifically designed for routine mailing and have different requirements.

Before collecting your sample, determine:

• Which carrier you are supposed to use

• Whether shipping is prepaid

• Whether pickup must be scheduled

• Whether the specimen must be shipped the same day

• Whether frozen packs are required

• Whether weekend shipping is permitted

• Whether a laboratory requisition must be placed inside the package

If your sample requires freezing, do not collect it immediately before a scheduled pickup unless it will have enough time to reach the required temperature.

Planning the shipping step before collection can prevent unnecessary recollection.

What Are the Most Common Sample Collection Mistakes?

Most specimen problems are preventable.

Common mistakes include collecting the specimen at the wrong time, using the wrong container, contaminating a urine or stool sample, forgetting part of a timed urine collection, collecting too little material, overfilling a preservative vial, failing to label the specimen, storing it at the wrong temperature, or waiting too long to ship it.

Patients may also unintentionally alter test conditions by changing medications or supplements without medical guidance.

The goal is not to collect a specimen perfectly according to a universal set of rules.

The goal is to collect your specimen according to the rules for your particular laboratory test.

What Should You Do If Something Goes Wrong?

Mistakes happen.

Perhaps you accidentally ate before a fasting test.

Maybe you missed one urine collection.

Your stool touched toilet water.

A tube leaked.

A frozen sample thawed.

You forgot to ship the package.

Or you realized after collection that you used the wrong container.

Do not hide the mistake and hope the laboratory will not notice.

Contact the laboratory or the healthcare professional who ordered the test.

Explain exactly what happened.

They may tell you that the specimen remains acceptable, or they may recommend recollecting it.

Either answer is better than receiving a result based on a specimen that did not meet the laboratory's collection requirements.

Wash Your Hands and Handle Specimens Carefully

Blood, urine, and stool are biological specimens.

Wash your hands before and after specimen collection.

Keep collection materials away from food-preparation areas, children, and pets.

Close specimen containers securely.

Use the provided transport bags and packaging materials.

Do not reuse lancets, collection needles, or other single-use equipment.

If a container leaks, breaks, or is visibly damaged, contact the laboratory for instructions rather than transferring the sample into a household container.

What Happens After the Laboratory Receives Your Sample?

Once the laboratory receives the specimen, staff may verify identifying information, evaluate whether the specimen meets collection requirements, prepare the sample, perform the ordered analysis, and report the results.

Turnaround time varies substantially.

Some tests may be completed relatively quickly, while complex specialty panels can require considerably more time.

A laboratory result should then be interpreted in the context of why the test was ordered.

An abnormal number does not automatically establish a diagnosis, and a normal result does not necessarily exclude every possible medical condition.

Results may need to be considered alongside:

• Your symptoms

• Medical history

• Previous laboratory results

• Medications and supplements

• Physical examination

• Imaging

• Other conventional testing

• Risk factors

• Lifestyle

• Relevant exposures

This is why specimen collection and physician interpretation are both important components of laboratory testing.

Frequently Asked Questions About Collecting Laboratory Samples

Can I refrigerate every urine or stool sample?

No. Storage requirements vary by test. Some specimens require refrigeration, others need freezing, and others should remain at room temperature. Follow the instructions from the laboratory.

Can stool be collected directly from the toilet?

Generally, the stool specimen should not be allowed to mix with toilet water or urine. Use the collection device or clean, dry method supplied or recommended for your specific test.

What if I do not collect enough stool?

Do not automatically add more later unless the laboratory instructions allow it. Contact the laboratory if you are unsure whether the quantity is sufficient.

What happens if I miss one collection during a timed urine test?

Contact the laboratory or ordering clinician. Missing part of a timed collection may affect the usefulness of the test, and recollection may sometimes be necessary.

Can I take my medications before collecting a laboratory sample?

Often yes, but medication timing depends on the test. Do not stop or change prescription medications unless your physician specifically instructs you to do so.

Can I ship a specialty laboratory kit on Friday?

It depends on the laboratory and specimen. Some specimens are stable during ordinary shipping, while others have strict temperature or transit-time requirements. Check the shipping instructions before collection.

What should I do if my sample becomes contaminated?

Contact the laboratory. Depending on the test and the type of contamination, the laboratory may recommend recollecting the specimen.

The Most Important Rule: Follow Your Specific Kit

General laboratory education can help you understand why collection matters, but your actual laboratory instructions should always come first.

If the kit says to freeze the specimen, freeze it.

If it says not to refrigerate it, do not refrigerate it.

If it requires a first-morning collection, follow that timing.

If a professional blood draw is required, do not attempt to substitute an at-home fingerstick.

If something goes wrong, ask before submitting the specimen.

Careful collection helps reduce avoidable problems and gives the laboratory the best opportunity to analyze the specimen under the conditions intended for that test.

Considering Specialty Laboratory Testing?

Specialty testing can provide additional information when it is selected to answer a meaningful clinical question and interpreted alongside your overall medical evaluation.

At Ask Dr. Hu, we use a physician-guided approach to testing rather than ordering large panels simply because they are available.

Testing may be selected according to your symptoms, medical history, previous results, medications, exposures, health goals, and the specific questions your physician is trying to answer.

Learn more about our Specialty Laboratory Testing services or explore additional physician-written articles and patient guides in our Specialty Laboratory Testing Resource Center.

If you would like help determining whether specialty laboratory testing is appropriate for you, contact Ask Dr. Hu.

Medical Sources, Editorial Standards, and Transparency

This patient guide was written and medically reviewed by YiQiu Hu, NMD, an Arizona-licensed naturopathic physician.

General laboratory-preparation information was reviewed using resources from the National Library of Medicine's MedlinePlus laboratory-testing guidance.

Clean-catch urine collection guidance is consistent with MedlinePlus patient guidance regarding urine specimen collection.

General principles regarding clean, dry stool collection and avoidance of urine or water contamination are consistent with Centers for Disease Control and Prevention stool specimen collection guidance.

Additional patient-oriented stool collection information was reviewed using MedlinePlus guidance on stool testing.

Important: Individual laboratories and individual tests may have different preparation, collection, storage, and shipping requirements. Instructions supplied by your ordering clinician and testing laboratory should take priority over general educational guidance.

Transparency statement: Ask Dr. Hu offers paid specialty laboratory testing and physician interpretation services and therefore has a financial interest in this topic. Our educational content is intended to help patients understand both the potential usefulness and the practical limitations of laboratory testing. We do not believe that every patient needs specialty testing or that more testing is automatically better.

Information on this page is provided for general educational purposes and does not replace individualized medical advice, diagnosis, or treatment.

Author: YiQiu Hu, NMD
Medical Review: YiQiu Hu, NMD
Last Reviewed: August 2026
Clinical Focus: Concierge medicine, naturopathic medicine, preventive healthcare, laboratory evaluation, health optimization, and individualized treatment planning

About the Author

YiQiu Hu, NMD

Dr. YiQiu Hu is an Arizona-licensed naturopathic physician, founder of Ask Dr. Hu, and medical director. His clinical work focuses on concierge medicine, preventive healthcare, health optimization, laboratory evaluation, chronic disease management, medical weight management, hormone care, and individualized treatment planning.

His approach to laboratory testing emphasizes selecting tests for a clear clinical purpose, interpreting results within the context of the patient's complete health history, and helping patients understand which findings are meaningful rather than treating laboratory reports as isolated numbers.

Learn more about Dr. YiQiu Hu and the physicians at Ask Dr. Hu.