Vitamin Studies


Vitamin A: retinol, carotene; Vitamin B1: thiamine; Vitamin B6: pyroxidine, P-5′-P, pyridoxyl-5-phosphate; Vitamin B12: cyanocobalamin; Vitamin C: ascorbic acid; Vitamin D: cholecalciferol, vitamin D 25-hydroxy, vitamin D 1,25-dihydroxy; Vitamin E: alpha-tocopherol; Vitamin K: phylloquinone, phytonadione.

To assess vitamin deficiency or toxicity to assist in diagnosing nutritional disorders such as malabsorption; disorders that affect vision, blood coagulation, skin, and bones; and other diseases.

Patient Preparation
There are no activity or medication restrictions unless by medical direction. Patient should fast overnight for 12 hr prior to specimen collection for vitamins A, B6, E, and K and should not consume alcohol for 24 hr prior to specimen collection for vitamins A, E, and K.

Normal Findings
Method: High-performance liquid chromatography: vitamins A, B1, B6, C, E, and K; Chemiluminescent Immunoassay: vitamin B12 and vitamin D.

AgeConventional UnitsSI Units
Vitamin A(Conventional Units × 0.0349)
Birth–1 mo14–52 mcg/dL0.49–1.81 micromol/L
2 mo–12 yr20–49 mcg/dL0.7–1.71 micromol/L
13–17 yr26–72 mcg/dL0.91–2.51 micromol/L
18 yr-Adult30–120 mcg/dL1.05–4.19 micromol/L
Vitamin B1
0.14–0.51 mcg/dL4–15 nmol/L
Vitamin B6(Conventional Units × 4.046)
5–30 ng/mL20–121 nmol/L
Vitamin B12(Conventional Units × 0.7378)
Adult180–914 pg/mL132.8–674.3 pmol/L
Vitamin C(Conventional Units × 56.78)
0.6–1.9 mg/dL34.1–107.9 micromol/L
Vitamin D 25-hydroxy(Conventional Units × 2.496)
DeficientLess than 20 ng/mLLess than 49.9 nmol/L
Insufficient20–29 ng/mL49.9–72.4 nmol/L
Optimal30–80 ng/mL74.9–199.7 nmol/L
Possible ToxicityGreater than 150 ng/mLGreater than 374.4 nmol/L
Vitamin D 1, 25-dihydroxy(Conventional Units × 2.6)
Adult20–80 pg/mL52–208 pmol/L
Vitamin E(Conventional Units × 2.322)
Newborn–1 mo1–3.5 mg/L2.3–8.1 micromol/L
2–5 mo2–6 mg/L4.6–13.9 micromol/L
6–12 mo3.5–8 mg/L8.1–18.6 micromol/L
13 mo–12 yr5.5–9 mg/L12.8–20.9 micromol/L
13 yr–Adult5–18 mg/L11.6–41.8 micromol/L
Vitamin KConventional Units × 2.22
Adult0.1–2.2 ng/mL0.22–4.88 nmol/L
Vitamin B1, vitamin B6, vitamin B12, and vitamin C levels tend to decrease in older adults. Sustained elevations of Vitamin D 25-hydroxy (greater than 50 ng/mL) in conjunction with ongoing calcium supplementation may result in hypercalciuria and decreased renal function.

Critical Findings and Potential Interventions
Timely notification to the requesting health-care provider (HCP) of any critical findings and related symptoms is a role expectation of the professional nurse. A listing of these findings varies among facilities.

Vitamin toxicity can be as significant as problems brought about by vitamin deficiencies. The potential for toxicity is especially important to consider with respect to fat-soluble vitamins (A, D, E, and K), which are not eliminated from the body as quickly as water-soluble vitamins and can accumulate in the body. Most cases of toxicity are brought about by oversupplementing and can be avoided by consulting a registered dietitian for recommended daily dietary and supplemental allowances. Signs and symptoms of vitamin A toxicity may include headache, blurred vision, bone pain, joint pain, dry skin, and loss of appetite. Signs and symptoms of vitamin D toxicity include nausea, loss of appetite, vomiting, polyuria, muscle weakness, and constipation. Excessive supplementation of vitamin E (greater than 60 times the recommended dietary allowance over a period of 1 yr or longer) can result in excessive bleeding, delayed healing of wounds, and depression. The naturally occurring forms vitamins K1 and K2 do not cause toxicity. Signs and symptoms of vitamin K3 toxicity include bleeding and jaundice. Possible interventions include withholding the source.

There's more to see -- the rest of this topic is available only to subscribers.