Cologuard Instructions: A Step-by-Step Walkthrough of the At-Home Test

Cologuard vs Other At-Home Stool Tests

Before unpacking the kit, it helps to know what Cologuard is doing differently from the older FIT and FOBT tests that have been around for decades.

The pattern: Cologuard is more sensitive than FIT, but less specific. That trade-off matters when you read your result and is the whole reason the instructions emphasize follow-up.

Who the Test Is For

Cologuard is FDA-approved for adults age 45 and older at average risk for colorectal cancer. The US Preventive Services Task Force lowered the start age from 50 to 45 in May 2021.

"Average risk" rules a lot of people out. The test is not appropriate if you have a personal history of colorectal cancer, advanced adenomas, or inflammatory bowel disease.

It is also not validated for people with a family history of colorectal cancer in a first-degree relative, certain hereditary syndromes (Lynch, familial adenomatous polyposis), or symptoms like rectal bleeding, unexplained iron deficiency anemia, or recent unintentional weight loss. People in those groups need a colonoscopy, not a stool test.

Instalab's Cologuard test ($599) ships the kit, processes the sample, and routes a positive result to follow-up care.

What the Kit Contains

When the box arrives, you should find five components: a sample bracket that fits across your toilet, a large sample container, a smaller probe tube of preservative liquid, a bottle of liquid preservative for the container, and a return shipping label with prepaid postage.

The bracket and container do the real work. Cologuard requires the entire stool sample, not just a smear, because the test looks for DNA shed by precancerous cells anywhere along the colon. A small smear from one spot would miss right-sided lesions, which is where about 80% of the neoplasia detected by mt-sDNA testing actually sits.

The Actual Collection Steps

The instruction card inside the kit reduces to four phases.

• Phase 1: register the kit. The box has a unique barcode. You call the number on the kit or go to the Cologuard website and link the barcode to your name and provider. If you skip this step, the lab has no way to send the result back to your doctor.
• Phase 2: collect the sample. Place the bracket across your toilet seat with the container locked into the bracket. Have a bowel movement directly into the container. Before you flush, take the small probe tube and scrape the stool, then seal the probe back into its tube and shake. The probe captures a representative DNA sample. Pour the bottle of preservative into the main container until it covers the stool, then close the container.
• Phase 3: pack and ship the same day. Drop it off or schedule a UPS pickup that same day. The preservative is designed to keep the DNA stable in transit, but the manufacturer's stability data is based on samples received at the lab within a few days.
• Phase 4: wait for results. Cologuard typically returns a result to your provider within two weeks of the lab receiving the sample. The result is binary: positive or negative.

The Cologuard instructions do not require any dietary restrictions, bowel prep, or fasting beforehand. This is a real practical advantage over colonoscopy and one reason adherence has been higher than expected.

What a Negative Result Means

A negative Cologuard result means the lab did not detect cancer-associated DNA markers or blood at a level above the test's threshold. In the pivotal validation trials, the next-generation Cologuard had a specificity of about 92% for people with no lesions, meaning roughly 8 out of 100 healthy people without disease will still get a positive result.

Negative does not mean cancer-free forever. It means cancer-free in a three-year window, which is the basis for the every-three-years repeat interval. The studies that established the repeat interval found that the positive predictive value of a second mt-sDNA test, three years after a negative first test, was essentially identical to the first test (24% for advanced precancerous lesions vs 28% on first round, no statistical difference).

In practical terms: if you get a negative result, mark your calendar for three years.

What a Positive Result Means

A positive Cologuard result is not a cancer diagnosis. It is a referral to colonoscopy. The instructions for what to do next are unambiguous: schedule a diagnostic colonoscopy.

Cologuard's positive predictive value sits around 27% for cancer or advanced precancerous lesions in the pivotal FDA approval study. That means roughly 1 in 4 positive results turns out to be a real lesion that the colonoscopy team needs to remove. The rest are false positives, often from bleeding hemorrhoids, menstrual blood that contaminated the sample, or DNA shed from non-cancerous tissue elsewhere in the digestive tract.

Real-world data show this follow-up step is where the screening pipeline often breaks down. In one analysis of 385 patients who tested positive on Cologuard, only 44% completed a colonoscopy within 12 months. A larger regional health system did better, with 68% of positive-result patients completing follow-up colonoscopy within a year. Either way, a meaningful share of people who get a positive result do nothing, which negates the whole reason for screening.

If your result is positive, the diagnostic colonoscopy is the test that actually finds and removes polyps. Skipping it after a positive Cologuard is the worst possible outcome.

How Many People Actually Complete the Kit

Adherence to the at-home portion is high by medical-test standards. Among 1.5 million insured adults shipped a Cologuard kit between January and June 2023, 71% returned a valid completed test within 365 days. Older adults (79% in the 76-85 age group) and people referred by a gastroenterologist (83%) had higher rates, while Medicaid patients had lower rates (52%).

For repeat screening at the three-year interval, adherence climbs even higher. A 2025 study of 793,567 patients in their second or later round of mt-sDNA testing found 84% returned the kit, with rates as high as 90% in Medicare.

Three observations from the adherence data help explain why the Cologuard instructions are written the way they are:

• Designed for solo use. The test was built to be completed without coming back to a clinical setting, which is why the kit is shippable and the preservatives are stable at room temperature.
• Navigation support matters. The calls and texts reminding people to ship the kit appear to add meaningfully to completion rates.
• Reach is the harder problem. The people most likely to complete the test are also the ones most likely to be screened by some other method anyway, so the population health gain depends heavily on bringing in patients who would otherwise skip screening entirely.

Common Reasons a Sample Gets Rejected

The lab can reject a sample if the preservative was not added, if too little stool was collected, if the sample arrived more than the validated transit window after collection, or if the barcode was not registered. The kit instructions include each of these checks, but rejection rates in real-world use have been a known operational issue. If your kit is rejected, the lab ships you a new one and you start over.

A few practical things the official instructions warn against, drawn from the labeling: Practical guidance from the labeling: avoid using the kit if you have visible blood in urine or stool from menstruation, hemorrhoids, or other sources, since blood from non-cancer sources can affect the FIT-blood component of the test.. Wait until the bleeding has resolved.

A Note on Cologuard Plus

In 2024, the FDA approved Cologuard Plus, the next-generation version. The instructions for the patient are essentially unchanged.

The technology change sits on the lab side, where Cologuard Plus uses an updated panel of DNA methylation markers that pushed cancer sensitivity to about 94% and improved specificity slightly compared to the original test. If your kit shipped after late 2024, it is probably the Plus version, though the difference is invisible from the patient's side.

What to Do With the Instructions in Front of You

The summary version: register the kit, collect the entire stool sample into the bracket-mounted container, add the preservative liquid, scrape the probe, seal everything, and ship the same day. No diet changes, no fasting, no bowel prep. Wait two weeks for a result. If negative, repeat in three years. If positive, get a colonoscopy.

The longer version is that the test is only as good as what happens after the result lands. A negative result lasts three years. A positive result requires a follow-up colonoscopy that real-world data say a third or more of people skip.

The kit's instructions handle the mechanical part well. The decision part, what to do after the result, is where the screening actually succeeds or fails.