Barium sulfate suspension
Barium sulfate suspensions are provided by a radiologist or radiographic technologist in advance of, or during a CT scan or fluoroscopic study to allow for better computer tomography of the gastrointestinal tract. The patient is instructed to take nothing by mouth, which means to abstain from eating and drinking (fasting), with the exception of drinking the barium sulfate suspension. The amount of time for this fast may vary, depending on the instructions given by the imaging facility and the area of the body to be scanned, but generally lasts for several hours prior to the scan. The patient generally skips one meal, along with abstaining from all liquids, clear or otherwise, during this time.
Consumption of the barium sulfate suspension begins 90 minutes to two hours prior to the CT/Flouroscopic scan, as instructed in the patient education provided. For a Barium Swallow or Dysphagiagram the barium is consumed after the study begins to discern if the patient has difficulties swallowing or masticating. Consumption is paced, beginning two hours before the scan is to occur, with levels marked on the provided container indicating how much is to be consumed between each of the two hours prior to the test. A small portion of the suspension is reserved for the minutes just before the test, to ensure that as much of the gastrointestinal tract as possible is coated.
After the scan is complete, the patient is encouraged to eat and drink normally, with special attention to plenty of fluids. The barium sulfate is excreted through defecation. Constipation is a possible side effect.
Taste and texture 
Barium sulfate suspensions could be described as having the consistency of a very thick glass of milk, or a very thin milkshake. Liquid chalk, with a not too unpleasant medicinal taste, is more accurate. The suspension is homogeneous, perfectly smooth, and white in color - very much like the color of milk. The suspension is stored at room temperature (labels suggest 25°C), so "warm, thick milk" is a common description of the general weight and consistency of the drink.
The taste is generally considered unpleasant, but not unbearably repulsive, and is dependent on the exact makeup of the drink. Descriptions range from "poor tasting, very runny vanilla pudding" to "mildly citrus, with a strong bitter aftertaste". In addition, the presence of the barium sulfate makes the drink have a mild acidic burning sensation. Because of the ease of the actual test, the paced two-hour consumption of the barium sulfate suspension is often considered the worst part of a CT scan.
Side effects 
Possible side effects are nausea and diarrhea, beginning roughly 15 minutes after consumption begins. For some patients, especially those drinking the suspension for the first time, the effect of the drink on the bowels may be moderately severe, so some times the required fasting period is voluntarily started earlier than a single meal before the test to allow for less contents in the stomach and bowels. Some patients with more sensitive stomachs may choose to discuss alternatives to the barium sulfate suspension with their radiologist, but most patients find this common side effect more of an annoyance than a serious problem.
The diarrhea and nausea may persist throughout the day after the test is completed, but returning to a normal diet helps limit this as much as possible. Patients are strongly warned to avoid vomiting, as expelling a substantial quantity of the suspension may void its effect on the CT scan and produce unusable results, requiring a retest.
Other side effects are generally limited to headaches.