Vitamins - Deficiency and Toxicity

Indications for Testing

Laboratory testing for vitamins is used to:

• Assess nutritional status (deficiency, sufficiency, or toxicity)
• Monitor therapeutic supplementation

Vitamin A

Vitamin A refers to a group of fat-soluble retinoids with the biologic activity of all-trans retinol, including retinol, retinal, retinoic acid, and retinyl esters.  Vitamin A is best known for its role in vision and eye health, but it is also important for immunity and reproduction. ^, ,  Vitamin A is found in animal foods, such as fish liver oils and liver, and occurs in the form of a carotenoid or provitamin A (eg, beta carotene) in plant foods, such as yellow- and orange-colored fruits and vegetables. ^,  Carotenoids are metabolized into vitamin A within the body.  Vitamin A deficiency is the leading preventable cause of childhood blindness throughout the world and is associated with significant morbidity and mortality from common childhood infections.  Deficiency may arise from bariatric surgery, fat malabsorption disorders (eg, celiac disease, Crohn disease), cystic fibrosis, and liver disease. ^,  Excessive preformed vitamin A in body stores (hypervitaminosis A) can occur as a result of chronic or acute excess intake, such as from consumption of supplements, and may lead to adverse consequences before symptoms become apparent. 

Laboratory Testing

Assessment of Status

Retinol or Associated Proteins in Serum or Plasma

Vitamin A concentration is tightly regulated in the circulation and may not decrease until liver stores are nearly depleted. ^,  Serum or plasma concentrations of retinol (the main circulating form of vitamin A) and/or the proteins that circulate with it (particularly retinol-binding protein) are widely used and considered sufficient to determine vitamin A status. ^,  Because retinol-binding protein is a negative acute-phase reactant, retinol concentration will decrease if inflammation is present; consider measurement of C-reactive protein (CRP) to distinguish between nutritional and inflammatory causes of reduced concentration.  Retinol-binding protein is also affected by liver disease, zinc deficiency, and protein malnutrition, all of which may lead to decreased plasma retinol concentration. 

Retinol Palmitate or Retinol Esters in Liver Tissue

The gold standard for the assessment of vitamin A status is evaluation of hepatic reserves via biopsy.  Hepatic reserves may also be indirectly assessed with plasma dose-response tests that involve evaluation of retinol in serum before and after administration of a small amount of vitamin A. ^, , 

Carotenoids in Plasma

Measurement of carotenoids (eg, beta [β]-carotene) in plasma can be a useful supplemental test for the assessment of vitamin A status but should not be used alone. 

Monitoring

Patients with a fat malabsorption disease who are receiving high-dose vitamin A supplementation should be monitored to verify proper dosing and avoid toxicity.

Patients with cystic fibrosis are particularly prone to malabsorption of fat-soluble vitamins, including vitamin A.  Many cystic fibrosis organizations recommend supplementation and careful monitoring. 

Regular monitoring is recommended for patients who have had bariatric surgery. Testing should also be considered if signs or symptoms of deficiency are present, regardless of how much time has passed since the surgery was performed. Refer to the ARUP Consult Bariatric Surgery - Nutritional Assessment topic for specific recommendations.

Vitamin B₁

Vitamin B₁, or thiamine (thiamin), is a water-soluble vitamin that is important in energy metabolism.  Sources of thiamine include meat, fish, whole grains, and fortified products (including infant formula).  The primary active form of thiamine in the body is thiamine diphosphate (TDP, also known as thiamine pyrophosphate).  Risk factors for thiamine deficiency include alcohol dependence, bariatric surgery, malabsorption, older age, and HIV/AIDS.  Because plasma thiamine concentration does not directly reflect thiamine concentration in tissue, plasma testing is not recommended for nutritional assessment; TDP should be measured in whole blood or erythrocytes instead.

Laboratory Testing

Assessment of Status

Vitamin B₆ testing is frequently ordered in conjunction with thiamine testing. Although plasma can be used for B₆ testing, B₁ tests will not yield accurate results in plasma; thus, whole blood is the preferred specimen when ordering both tests.

Thiamine Diphosphate in Erythrocytes or Whole Blood

TDP can be measured in erythrocytes or whole blood and is the preferred analyte for assessment of thiamine status.  Erythrocyte thiamine concentration reflects thiamine status, and whole blood concentration correlates well with erythrocyte concentration, especially when corrected for hemoglobin. 

Thiamine and Thiamine Monophosphate in Plasma or Serum

Free thiamine and thiamine monophosphate can be measured in plasma or serum.  However, concentrations in plasma reflect recent intake, not body stores.  Therefore, measurement of TDP in erythrocytes or whole blood is the preferred test for evaluating vitamin B₁ stores.

Thiamine Transketolase Activity in Erythrocytes

Erythrocyte thiamine transketolase activity was previously measured to indirectly assess tissue thiamine stores.  However, this activity test is no longer routinely performed in the United States. Instead, direct measurement of thiamine in erythrocytes or whole blood is preferred. 

Thiamine in Urine

Although not widely used, tests for excreted thiamine in urine may help determine thiamine intake. However, urine thiamine concentration does not reflect tissue stores.  Urinary concentration of thiamine in a 4-hour specimen compared before and after a test load of thiamine may assist in determining thiamine status. 

Monitoring

Regular monitoring is recommended for patients who have had bariatric surgery and have risk factors for thiamine deficiency. Testing should also be considered if signs or symptoms of deficiency are present, regardless of how much time has passed since the surgery was performed. Refer to the ARUP Consult Bariatric Surgery - Nutritional Assessment topic for specific recommendations.

Serial measurements of thiamine (eg, in patients with Wernicke-Korsakoff syndrome) should be performed using the same assay, preferably using a whole blood specimen.

Vitamin B₂

Vitamin B­₂ (riboflavin) is a water-soluble vitamin that is a critical part of the flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) coenzymes, which are involved in energy production and numerous other metabolic and cellular functions.  Sources of riboflavin include organ meats, lean meats, eggs, milk, green vegetables, and fortified grain products.  Risk factors for riboflavin deficiency include endocrine disorders (eg, thyroid hormone insufficiency), vegan diet, vegetarian diet (in athletes), low consumption of meat or dairy products during pregnancy, and riboflavin transporter deficiency neuropathy.  Riboflavin deficiency is often associated with deficiency in other B vitamins because riboflavin plays a role in the activation of vitamins B₃ and B₆.  Testing of riboflavin status is not routinely performed in healthy individuals. 

Laboratory Testing

Assessment of Status

Riboflavin and Metabolites in Erythrocytes, Plasma, or Whole Blood

Direct measurement of riboflavin and its metabolites (FAD and FMN) can be made in erythrocytes, plasma, or whole blood.  All of these measurements except for FAD concentration in plasma are considered adequate indicators of B₂ status.  FAD measurements in plasma are affected by inflammation; therefore, testing for erythrocyte FAD concentration is recommended in critically ill patients. 

Erythrocyte Glutathione Reductase Activity Coefficient

The erythrocyte glutathione reductase activity coefficient is an indirect but sensitive measure of riboflavin status.  Erythrocyte glutathione reductase activity is measured as the ratio of erythrocyte glutathione reductase in freshly lysed erythrocytes without and with stimulation with exogenous FAD. ^,  Thresholds for diagnosing deficiency have not been firmly established,  however, and variation between methods may lead to differences in results.  This assay is not useful in patients with glucose-6-phosphate dehydrogenase deficiency. 

Riboflavin in Urine

Fluorometrically measured urine riboflavin excretion reflects recent intake, although concentration may be affected by age, stress, and certain drugs. 

Vitamin B₃

Vitamin B₃ (niacin) is a collective term for nicotinic acid, nicotinamide, and derivatives with the same biologic activity.  The main active form of niacin is the coenzyme nicotinamide adenine dinucleotide (NAD), which is converted into nicotinamide adenine dinucleotide phosphate (NADP), both of which are required for numerous enzymatic reactions within the body.  Sources of niacin include beans, eggs, meat, milk, fish, nuts, grains, and fortified grain products.  Risk factors for niacin deficiency include malabsorption; inflammatory bowel disease; vitamin B₂, B₆, or iron deficiency; alcohol dependence; anorexia; cirrhosis of the liver; HIV/AIDS; carcinoid syndrome; and Hartnup disease.  Very high-dose niacin is used as a medication for hyperlipidemia and other conditions. 

Laboratory Testing

Assessment of Status

Niacin in Plasma

Niacin concentration may be measured in plasma, although plasma concentration is not a reliable indicator of niacin status. ^, 

Monitoring

Niacin may lead to adverse side effects when taken in pharmacologic doses; therefore, multiple organizations recommend testing hepatic transaminase, fasting blood glucose or hemoglobin A1c, and uric acid in supplement users before the initiation of therapy, when dosage is increased, and every 6 months after reaching a maintenance dose. 

Vitamin B₅

Vitamin B₅ (pantothenic acid) is a water-soluble vitamin that is required for the synthesis of coenzyme A (CoA), a critical coenzyme in numerous reactions within the body.  Sources of pantothenic acid include whole grains, some vegetables, meats, fortified cereals and drinks, and other plant- and animal-derived foods.  Although pantothenic acid status is not usually assessed in healthy individuals, it can be measured by a variety of assays in blood, urine, and tissue. 

Laboratory Testing

Assessment of Status

There are currently no widely used functional tests for pantothenic acid. 

Pantothenic Acid in Serum or Plasma

Serum or plasma contains only the free pantothenic acid form, rather than the active form, and does not accurately reflect pantothenic acid intake or status. ^,  Pantothenic acid serum or plasma testing is primarily used for investigational purposes.

Vitamin B₆

Vitamin B₆ is a general term for pyridoxine, pyridoxamine, pyridoxal, and their esters. Pyridoxal 5’ phosphate (PLP) and pyridoxamine 5’ phosphate are the active forms and are involved in numerous enzymatic reactions; 4-pyridoxic acid is a catabolic product of vitamin B₆ metabolism. ^,  Sources of vitamin B₆ include meats, whole grains, fish, vegetables, nuts, noncitrus fruits, and fortified grain products. ^,  Although studies have shown that almost a quarter of people in the U.S. have low plasma PLP concentrations,  clinically relevant vitamin B₆ deficiency is rare in otherwise healthy individuals and usually occurs in conjunction with other B vitamin deficiencies. Risk factors for deficiency include obesity, malabsorption (eg, due to celiac disease or Crohn disease), pregnancy, hemodialysis, alcohol dependence, chronic renal insufficiency, and pyridoxine-dependent epilepsy.  Vitamin B₆ supplements may be used to treat nausea and vomiting in pregnancy.  Testing for vitamin B₆ includes the measurement of PLP or other forms of vitamin B₆ in urine, plasma, or whole blood.

Laboratory Testing

Assessment of Status

No single marker reflects vitamin B₆ status; therefore, use of a combination of tests is recommended.  Thiamine (vitamin B₁) testing is frequently ordered in conjunction with B₆ testing. Although plasma can be used for B₆ testing, B₁ tests will not yield accurate results in plasma; thus, whole blood is the preferred specimen when ordering both tests.

Pyridoxal 5’ Phosphate in Plasma or Erythrocytes

PLP concentration in plasma is the most common measure of vitamin B₆ status  and may be the best indicator of tissue stores, given that it is thought to reflect the concentration of PLP in liver.  Increases in PLP concentration in plasma occur within 3 days of supplementation. 

4-Pyridoxic Acid in Plasma

4-pyridoxic acid is a product of vitamin B₆ metabolism. Increases in 4-pyridoxic acid concentration in plasma occur within 3 days of supplementation.  Reduced concentration may be observed in vitamin B₆ deficiency.

Homocysteine in Plasma

Plasma homocysteine is elevated in individuals with suboptimal vitamin B₆, B₉, or B₁₂ status, or impaired renal function. 

Aspartate Aminotransferase and Alanine Aminotransferase Functional Testing in Erythrocytes

Erythrocyte aspartate aminotransferase and erythrocyte alanine aminotransferase can be activated with PLP to evaluate long-term B₆ status.  However, results may vary based on the method used, and variability is greater for vitamin B₆ assays than it is for corresponding assays for vitamins B₁ and B₂.  For more information on liver enzyme tests, see Liver Disease Evaluation.

PLP is used as an activating reagent in some alanine aminotransferase assays for the evaluation of liver disease.  Thus, if a patient has an abnormal vitamin B₆ status, there is the potential for misinterpretation of liver function tests results.

Vitamin B₇

Vitamin B₇, or biotin, is a cofactor for enzymes involved in metabolism and is also involved in histone modification, cell signaling, and gene regulation.  Sources of biotin include meats, fish, nuts, and some vegetables.  Dietary biotin deficiency is rare but can occur in individuals with biotinidase deficiency.  Other risk factors include malabsorption, pregnancy, breastfeeding, and alcohol dependence. 

Laboratory Testing

Assessment of Status

Biotin supplements, many containing more than 500 times the recommended daily intake of biotin, are promoted to improve hair, skin, and nail health.  Such high-dose supplementation may interfere with laboratory tests that use biotin-streptavidin to measure analyte concentrations.  For more information, including a list of tests potentially affected by biotin interference, see the ARUP Laboratories Biotin Interference page.

Biotin in Plasma or Serum

Measurement of biotin in plasma or serum assesses biotin concentration but does not indicate biotin status.  Low biotin concentrations in plasma and serum are not sensitive markers of inadequate biotin intake because they do not decrease substantially with mild biotin deficiency. ^, 

Vitamin B₉

Vitamin B₉ (folate, folic acid, or folacin) is essential for gene expression and cell division.  Sources of folate include fortified breads, fortified cereals and grain products, fruits, leafy green vegetables, and dried legumes. ^,  Risk factors for folate deficiency and corresponding megaloblastic anemia include malabsorptive disorders (celiac disease, tropical sprue, Crohn disease), alcohol dependence, SLC46A1 (protein-coupled folate transporter) variants, and the 677C>T MTHFR gene variant. ^, ,  Folate deficiency is usually accompanied by deficiency of multiple other nutrients, especially vitamin B₁₂; folate supplementation is thought to mask the symptoms of vitamin B₁₂ deficiency.  Pregnant women require increased folate intake to reduce the risk of neural tube defects in their infants. 

Laboratory Testing

Assessment of Status

Coexisting iron deficiency or vitamin B₁₂ deficiency may interfere with the diagnosis of folate deficiency, given that supplemental folate may treat the anemia associated with B₁₂ and folate deficiency while allowing progression of neurologic complications of B₁₂ deficiency. ^, 

Folate in Serum or Plasma

Measurement of folate in serum or plasma is the preferred initial test for folate status,  although results may reflect recent dietary intake of folate. Assessment of cobalamin (vitamin B₁₂) and folate status is often performed concurrently because the biochemical pathways for the two vitamins are closely related, and deficiency of either vitamin results in similar clinical features.  Serum folate testing is preferred over erythrocyte folate in cases of vitamin B₁₂ deficiency. 

Folate in Erythrocytes

Erythrocyte folate concentration is a longer-term indicator of folate intake than serum folate.  Because the folate content of red blood cells is fixed during erythropoiesis, erythrocyte folate is indicative of folate status over the preceding 120 days. ^, 

Homocysteine in Plasma

Plasma homocysteine concentration increases in cases of folate deficiency, although it may also be elevated due to vitamin B₆ or B₁₂ deficiency or other factors (eg, impaired renal function). ^,  Thus, plasma homocysteine can be used as a nonspecific functional indicator of folate status, particularly in combination with serum or erythrocyte folate. 

Monitoring

Regular monitoring is recommended for patients who have had bariatric surgery. Testing should also be considered if signs or symptoms of deficiency are present, regardless of how much time has passed since the surgery was performed. Refer to the ARUP Consult Bariatric Surgery - Nutritional Assessment topic for specific recommendations.

Vitamin B₁₂

Vitamin B₁₂, or cobalamin, is the name for several forms of cobalt-containing compounds with vitamin B₁₂ activity.  Cobalamins, specifically the active forms methylcobalamin and 5-deoxyadenosylcobalamin, are essential coenzymes for methyl transfer reactions in the body.  Vitamin B₁₂ is also necessary for proper blood formation, DNA synthesis, and neurologic health.  Sources of vitamin B₁₂ include animal products, dairy products, and fortified products. ^,  Although most people in the U.S. consume more than the recommended amounts of vitamin B₁₂, vitamin B₁₂ deficiency is still a common condition and may lead to megaloblastic anemia.  Risk factors for vitamin B₁₂ deficiency include short bowel syndrome, alcohol dependence, vegan diet, gastrointestinal disorders (eg, celiac disease), older age, pernicious anemia, and low stomach acidity. ^, 

Laboratory Testing

Assessment of Status

Long-term consumption of large amounts of folic acid (folate) may delay the diagnosis of anemia in the case of vitamin B₁₂ deficiency, which may increase the risk of neurologic damage. 

Vitamin B₁₂ in Serum or Plasma

A variety of methods are used to determine the concentration of vitamin B₁₂ in serum or plasma.  Serum or plasma B₁₂ concentration reflects both intake and stores.  However, serum concentrations may be maintained even when tissue stores are depleted; thus, although a low concentration may indicate a long-term abnormality or low intake, an adequate concentration does not necessarily indicate adequate tissue stores.  Concentration in serum or plasma may be abnormally high if the patient has received vitamin B₁₂ injections within the 2 weeks before the test.

Methylmalonic Acid in Serum, Plasma, or Urine

Insufficient vitamin B₁₂ causes methylmalonic acid (MMA) concentration to rise.  Because elevated MMA concentration is tightly correlated with vitamin B₁₂ status, MMA concentration might be a more sensitive, more reliable, and earlier indicator of vitamin B₁₂ deficiency than vitamin B₁₂ plasma concentration. ^,  Furthermore, MMA concentration is not affected by folate deficiency and is therefore more specific than other indirect measures of vitamin B₁₂ status.  MMA concentration is increased in individuals with impaired renal function and in older individuals (>65 years of age) in the absence of B₁₂ deficiency. ^, 

Homocysteine in Plasma

Plasma homocysteine concentration may increase in the case of vitamin B₁₂ deficiency, although it may also be elevated due to vitamin B₆ or folate deficiency or other factors (eg, impaired renal function). ^,  Thus, plasma homocysteine can be used as a nonspecific indicator of B₁₂ status, particularly in combination with other tests.

Monitoring

Monitoring for vitamin B₁₂ deficiency should be considered for the following patients:

• Patients who have had bariatric surgery; refer to the ARUP Consult Bariatric Surgery - Nutritional Assessment topic for specific recommendations
• Individuals using metformin, particularly those with anemia or peripheral neuropathy 
• Individuals using proton pump inhibitors for prolonged periods 

Vitamin C

Vitamin C (ascorbic acid), a key antioxidant within the body, is involved in a variety of biosynthetic reactions and plays a role in immunity and iron absorption. ^,  Sources of vitamin C include fruits (especially citrus fruits), vegetables, and fortified grains. ^,  Vitamin C deficiency and toxicity are rare in the U.S. Insufficiency, however, may be present in infants not receiving breast milk or formula and in individuals who smoke, consume a diet with limited food variety, or have certain medical conditions (eg, cancer). ^,  High-dose vitamin C may be provided intravenously for therapeutic purposes in patients with cancer. 

Laboratory Testing

Assessment of Status

There are currently no widely used functional indicators of vitamin C status; direct measurements are used instead.  Vitamin C is light, temperature, and oxidant sensitive, and is unstable in plasma.  Addition of a preservative should be considered,  and samples should be carefully prepared and rapidly frozen to minimize exposure to light and heat.

Vitamin C in Plasma, Serum, or Urine

Vitamin C status is usually measured via high-performance liquid chromatography with electrochemical detection as total ascorbic acid in plasma or serum, although other detection methods can be used.  Measurements in plasma and serum indicate the availability of circulating vitamin C and are considered reliable indicators of intake. ^,  However, concentration of vitamin C in plasma or serum may be extremely high if the patient is receiving intravenous vitamin C for therapeutic purposes. Urine ascorbic acid concentration following a load of vitamin C may be useful in the diagnosis of scurvy. 

Vitamin C in Leukocytes

Ascorbic acid may also be measured in buffy coat or leukocytes.  Vitamin C in leukocytes may reflect the tissue vitamin C concentration more accurately than plasma measurements.  However, the performance of these assays is difficult; thus, they are not widely used. 

Vitamin D

Vitamin D (calciferol) is the collective name for a group of fat-soluble compounds that includes ergocalciferol (vitamin D₂) and cholecalciferol (vitamin D₃). Vitamin D functions as a hormone precursor and is required for calcium absorption, bone metabolism, and regulation of cell development and immune function.  Unlike other vitamins, vitamin D in the body may be derived from the diet or may be synthesized in the skin in response to sun exposure.  The body converts vitamin D into 25-hydroxyvitamin D [25(OH)D], its major circulating form, and 1,25-dihydroxyvitamin D [1,25(OH)₂D], its major active form.  Vitamin D testing includes testing for 25-hydroxyvitamin D (the preferred test for nutritional status), as well as measurement of 1,25-dihydroxyvitamin D [25(OH)₂D] (discouraged unless the patient has hypercalcemia or decreased kidney function).  For specific recommendations on vitamin D monitoring following bariatric surgery, refer to the ARUP Consult Bariatric Surgery - Nutritional Assessment topic.

Vitamin E

Vitamin E is a term for the group of antioxidant tocopherols and tocotrienols.  Vitamin E occurs in eight forms, including alpha (α)-tocopherol and gamma (γ)-tocopherol. In addition to its antioxidant activity, vitamin E is involved in immunity, cell signaling, gene regulation, and metabolism.  Sources of vitamin E include seeds and nuts, vegetable oils, leafy green vegetables, and fortified products.  Risk factors for deficiency include fat malabsorption disorders (eg, Crohn disease, cystic fibrosis), and abetalipoproteinemia. ^, 

Laboratory Testing

Assessment of Status

Vitamin E in Serum or Plasma

Alpha- and γ-tocopherol are the vitamers most commonly used to assess vitamin E status.  High-performance liquid chromatography is the preferred method for measuring vitamin E in serum or plasma. 

Monitoring

Patients with cystic fibrosis are particularly prone to malabsorption of fat-soluble vitamins, including vitamin E.  Many cystic fibrosis organizations recommend supplementation and careful monitoring. 

Testing for vitamin E status in patients who have had bariatric surgery should be considered if signs or symptoms of deficiency are present, regardless of how much time has passed since the surgery was performed. Refer to the ARUP Consult Bariatric Surgery - Nutritional Assessment topic for specific recommendations.

Vitamin K

Vitamin K refers to fat-soluble compounds with a 2-methyl-1,4-naphthoquinone structure, including phylloquinone (K₁) and menaquinone (K₂).  Vitamin K is necessary for the formation of blood clots and bone metabolism, among other functions.  Phylloquinone is found in leafy green vegetables, whereas sources of menaquinone include bacteria (which synthesize menaquinone in the human gut), animal foods, and fermented foods.  Vitamin K deficiency is rare in adults, generally a result of malabsorption, cystic fibrosis, or liver disease, and is only clinically problematic when clotting time is increased. ^,  Newborns, however, may be born without sufficient vitamin K stores, leading to excessive bleeding. The American Academy of Pediatrics recommends that all newborns receive a one-time intramuscular dose of vitamin K.  Laboratory testing for vitamin K is generally not performed except in patients taking anticoagulant medication or with a bleeding disorder. 

Laboratory Testing

Assessment of Status

Phylloquinone in Serum or Plasma

Fasting serum or plasma phylloquinone concentration correlates with intake and is considered the best indicator of vitamin K₁ status. ^,  However, this test does not assess menaquinone (K₂), and patients with low phylloquinone concentration may not exhibit clinical symptoms of vitamin K deficiency. 

Vitamin K Indirect Functional Tests

Vitamin K status is generally determined indirectly by measuring the function of vitamin K-dependent proteins. ^,  Plasma prothrombin time (PT) and the international normalized ratio (INR, an expression of the prothrombin time as a fraction of control time) are the most commonly used tests.  PT and INR increase in the case of vitamin K deficiency, reflecting clinically significant reduced clotting ability. 

Monitoring

Functional vitamin K tests (eg, INR) are commonly used for monitoring in warfarin dosing and in bleeding disorders. For more information, refer to the ARUP Consult Prolonged Clotting Time Evaluation, Hemophilia, and Uncommon Factor Deficiencies topics.

Patients with cystic fibrosis are particularly prone to malabsorption of fat-soluble vitamins, including vitamin K.  Many cystic fibrosis organizations recommend supplementation and careful monitoring.  If liver disease is present, PT testing is recommended at 2 months after the initiation of supplementation and annually thereafter, or more often if results are abnormal. 

Testing for vitamin K status in patients who have had bariatric surgery should be considered if signs or symptoms of deficiency are present, regardless of how much time has passed since the surgery was performed. Refer to the ARUP Consult Bariatric Surgery - Nutritional Assessment topic for specific recommendations.