Vitamin Deficiencies on the NCLEX
B12, folate, D, C, K, and thiamine: who gets deficient and what you find.
Six vitamins carry almost all the deficiency questions. Learn the at-risk patient and the classic finding for each.
B12 (cobalamin)
At risk: pernicious anemia (no intrinsic factor), gastrectomy or gastric bypass, ileal resection or Crohn's disease, vegans, long-term metformin or PPI use. Findings: macrocytic anemia PLUS neuro signs: paresthesias, ataxia, loss of position sense, glossitis. Pernicious anemia needs parenteral or high-dose B12 for life; diet alone cannot fix an absorption problem.
Folate
At risk: alcohol use disorder, pregnancy, malnutrition, methotrexate, phenytoin, sulfasalazine. Findings: macrocytic anemia WITHOUT neuro signs. That one word separates it from B12 on the exam. Pregnancy needs 400 mcg daily before conception to prevent neural tube defects. Sources: leafy greens, fortified grains, legumes, citrus.
Vitamin D
At risk: homebound and long-term-care elders, CKD (failed activation), malabsorption, dark skin with low sun exposure, exclusively breastfed infants without supplementation. Findings: rickets in children, osteomalacia and osteoporosis in adults, bone pain, hypocalcemia. Sources: sunlight, fortified milk, fatty fish.
Vitamin C
At risk: diets with no fruits or vegetables, alcohol use disorder, smokers. Findings (scurvy): bleeding gums, petechiae, easy bruising, poor wound healing, joint pain. Vitamin C also boosts iron absorption, which is why OJ with iron tablets is a tested pairing.
Vitamin K
At risk: newborns (sterile gut, hence the IM vitamin K injection at birth), liver disease, prolonged broad-spectrum antibiotics, fat malabsorption. Findings: bleeding and a prolonged PT/INR. Vitamin K is the warfarin antidote, and dietary vitamin K (leafy greens) is why warfarin patients keep intake consistent.
Thiamine (B1)
At risk: alcohol use disorder above all, plus severe malnutrition and hyperemesis gravidarum. Findings: Wernicke encephalopathy (confusion, ataxia, ophthalmoplegia) and beriberi. The tested rule: give thiamine before or with IV glucose in at-risk patients, because glucose without thiamine can precipitate Wernicke.
Frequently asked
B12 vs folate on a stem?
Both give macrocytic anemia. Neuro symptoms mean B12. Treating B12 deficiency with folate alone fixes the blood but lets the neuro damage progress.
Which are fat-soluble?
A, D, E, K. They need dietary fat and bile to absorb, and they can build to toxicity because the body stores them.
Why does CKD cause vitamin D deficiency?
The kidney performs the final activation step. Failed kidneys mean inactive vitamin D, low calcium, and renal bone disease.
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