Nutrient deficiencies in patients who have had restrictive procedures have been reported although the exact prevalence is unknown. Because procedures like sleeve gastrectomy retain the use of the entire gastrointestinal tract, nutrient deficiencies are less common than in patients who have had gastric bypass procedures.After gastric bypass procedures, patients are prone to deficiencies of the fat-soluble vitamins (A, D, E, and K) and calcium. In addition, these patients have an increased risk of developing anaemia secondary to potentially inadequate amounts of iron, vitamin B12, and folate. Because of these deficits, all patients should receive a daily multivitamin and calcium supplementation indefinitely. In patients with anaemia, additional supplementation with iron, vitamin B12, and folate may be necessary.The partitioning of the stomach during bariatric surgery results in a dramatic decrease in the production of hydrochloric acid, affecting the absorption of calcium and iron. Decreased calcium absorption can increase the risk of osteoporosis.
Calcium carbonate depends on acid for its absorption; calcium citrate does not. Hence Calcium citrate is the preferred option for replacement.The duodenum is the primary site for absorption of iron and is bypassed in gastric bypass procedures, creating the potential for nutrient deficiencies. To be absorbed, iron must be in the ferrous state (Fe2+). However, most consumed iron is in the ferric form (Fe3+) and reduced to the ferrous state in the acidic environment of the stomach. The ferrous form is then absorbed in the duodenum. In patients who have had gastric bypass surgery, iron salts can be combined with ascorbic acid (vitamin C) to acidify the stomach environment and facilitate absorption. There are commercially available products that combine these two nutrients.
Vitamin B12 absorption is dependent on the presence of intrinsic factor, which is produced in the parietal cells of the stomach. In addition, hydrochloric acid is necessary to cleave vitamin B12 from protein in the stomach. These variations can lead to deficiencies in patients after gastric bypass surgery. Monthly B12 injections are effective however, appropriate supplementation can also be achieved by using the oral formulation (1000 µg daily).  This helps these patients avoid the inconvenience of frequent health care visits and the pain associated with injections.Ulceration in a patient after gastric bypass and bleeds have been reported with the use of nonsteroidal anti-inflammatory drug. 
Most bariatric surgery centres in the US recommend that patients avoid the use of these agents indefinitely to avoid this potentially fatal complication.Other options for oral pain medication include paracetamol, opioids, and tramadol.Decreased intestinal length and surface area after a gastric bypass leads to the reduced absorption of extended-release drug preparations because these formulations are absorbed over 2 to12 hours. The reduction in functional intestine length makes it likely that extended-release preparations have passed through the gastrointestinal tract before absorption is complete. These same principles can also apply to delayed-release and enteric- or film-coated product formulations. To overcome this problem, patients need to take the regular immediate-release dosage forms, which could require increased frequency of administration. Of course this needs supervision of your general practitioner.