Getting a CT scan starts with a doctor’s order. In the United States, you cannot walk into an imaging center and request one on your own. A physician, nurse practitioner, or other qualified provider must determine that the scan is medically necessary, write the order, and specify what body part needs to be imaged. From there, the process involves insurance approval, scheduling, and a short appointment that typically takes about a minute of actual scan time.
Why You Need a Doctor’s Order
CT scans use X-ray radiation, and the FDA regulates them accordingly. Before ordering one, your provider is expected to confirm that the scan is necessary to answer a specific clinical question, that alternatives using less or no radiation (like ultrasound or MRI) aren’t suitable, and that you haven’t already had a recent scan that would make this one redundant. This isn’t just a formality. It’s a safety check built into federal guidelines.
If you don’t already have a doctor raising the possibility of a CT scan, start with your primary care provider. Describe your symptoms, and they’ll decide whether imaging is warranted. If your situation calls for it, they may refer you to a specialist who then orders the scan. In an emergency, the process is much faster: an ER physician can order a CT scan on the spot and have results within the same visit.
Conditions That Typically Call for a CT Scan
Doctors order CT scans for a wide range of problems. Common reasons include suspected broken bones, internal bleeding, kidney stones, blood clots, appendicitis, bowel blockages, brain and spinal cord injuries, heart disease, pneumonia, and cancer. CT is particularly useful in emergencies because the scan itself is fast and produces highly detailed images. It’s often preferred over MRI for trauma cases, such as car accidents or falls, where speed matters and fractures need to be ruled out quickly. People who can’t have an MRI due to metal implants or pacemakers are also typically routed to CT instead.
Insurance and Prior Authorization
Most insurance plans cover CT scans that are deemed medically necessary, but many require prior authorization before the scan takes place. This means your doctor’s office submits a request along with supporting medical documentation explaining why the scan is needed. The insurance company reviews it and sends back an approval or denial, usually within a few business days. For Medicare, the process works the same way: providers submit the request to their Medicare contractor and receive a decision before rendering services.
If you’re uninsured or paying out of pocket, where you go makes a significant difference in cost. Hospital-based CT scans typically run $1,500 to $3,000 or more, while outpatient imaging centers and urgent care facilities charge $300 to $1,200 for the same scan. Outpatient centers also tend to offer more transparent pricing with fewer surprise charges. If your doctor gives you a choice of facilities, it’s worth calling ahead to compare prices.
How to Prepare for Your Scan
Preparation depends on what type of CT scan you’re having. Many scans require no special prep at all. If your scan uses contrast dye (a substance injected into a vein to make certain structures more visible), current guidelines from both European and American radiology organizations say that fasting beforehand is not required for routine IV contrast. This is a change from older practices, and some facilities haven’t updated their instructions, so you may still be told to skip meals. The one exception is scans of the stomach or small intestine, which may require fasting for four to eight hours and drinking a large volume of water beforehand.
If you’re getting contrast, your doctor may check your kidney function with a blood test first. Contrast dye is processed by the kidneys, and people with reduced kidney function face a higher risk of a complication called contrast-induced kidney injury. The key measurement is your estimated glomerular filtration rate, or eGFR, which tells your doctor how well your kidneys are filtering. Patients with an eGFR below 60 are considered higher risk and may need extra IV fluids before and after the scan, or your doctor may choose a different type of imaging altogether. If your kidney function is stable, a blood test within the past three months is generally sufficient. For acute illness or hospitalized patients, it should be within seven days.
Staying well hydrated in the 6 to 12 hours before a contrast scan and for 24 hours afterward is encouraged for everyone, especially those at higher risk of kidney complications.
What Happens During the Scan
The scan itself is straightforward. You’ll lie on a flat table that slides into a large, donut-shaped machine. Unlike an MRI, the opening is wide and shallow, so claustrophobia is rarely an issue. The actual imaging takes roughly one minute, though your total time in the room will be longer as the technologist positions you and runs through any contrast injection. You may be asked to hold your breath briefly. If contrast is used, you might feel a warm sensation or a metallic taste in your mouth for a few seconds. The whole visit, from check-in to walking out, typically takes 15 to 30 minutes.
Getting Your Results
After the scan, a radiologist reviews the images and writes a report that goes to the doctor who ordered the scan. For emergency scans, preliminary results can come within minutes. For outpatient scans, expect results within one to three business days, though some facilities are faster. Many health systems now post imaging reports to online patient portals, so you may see the radiologist’s report before your doctor calls. If the language in the report is confusing, wait to discuss it with your ordering physician, who can explain what the findings mean for your specific situation and what comes next.
ER Versus Outpatient: Two Different Paths
If you’re experiencing a medical emergency, such as sudden severe abdominal pain, signs of a stroke, major trauma, or difficulty breathing, go to the emergency room. The ER physician can order and perform a CT scan immediately without any prior authorization or scheduling. Results are read in real time, and treatment decisions happen the same day. The tradeoff is cost: ER visits come with facility fees on top of the imaging charges, making them significantly more expensive than a planned outpatient scan.
For non-urgent concerns, the outpatient route is almost always better. Your doctor writes the order, insurance authorization is handled, and you schedule the scan at a time that works for you, often at a standalone imaging center where prices are lower and wait times shorter. The images are the same quality either way.