Is measuring vitamin C (Ascorbic Acid) levels clinically significant?

From the Guidelines

Testing vitamin C levels is only clinically significant in specific situations, such as suspected scurvy or chronic low intake, as recommended by the most recent guideline 1. When considering the clinical significance of testing vitamin C levels, it's essential to prioritize situations where deficiency is likely to have a significant impact on morbidity, mortality, and quality of life.

• The general population consuming a varied diet with fruits and vegetables does not require routine vitamin C testing, as deficiency is uncommon in developed countries.
• High-risk individuals, such as those with malnutrition, alcoholism, or certain medical conditions, may benefit from vitamin C testing if deficiency is suspected.
• In cases of suspected scurvy or chronic low intake, measuring plasma vitamin C concentrations is recommended 1, and a clinical trial of vitamin C supplementation should not be delayed in the presence of clinical symptoms.
• However, measurement of plasma vitamin C is not recommended in critical illness or severe inflammation due to the difficulty in interpretation of results 1.
• If testing is needed, serum or plasma vitamin C levels can be measured, with normal ranges typically between 0.4-2.0 mg/dL (23-114 μmol/L).
• Most people can maintain adequate vitamin C status by consuming the recommended daily allowance of 75-90 mg for adults, which is easily achieved through diet or basic supplementation without the need for monitoring blood levels.

From the Research

Clinical Significance of Vitamin Testing

• The testing of vitamins, such as vitamin C, can be clinically significant in certain cases, particularly in the diagnosis and treatment of scurvy 2, 3, 4.
• Scurvy is a nutritional disorder that can develop after prolonged severe vitamin C deficiency, and its symptoms can be nonspecific, making early recognition difficult 2, 3, 4.
• Laboratory testing for vitamin C concentration is not necessary to confirm scurvy, as it tends to reflect recent dietary intake of vitamin C, but it may be useful to identify less typical cases 2.

Risk Factors and Diagnosis

• Risk factors for scurvy development include undernutrition, low socioeconomic status, older age, male sex, alcoholism, tobacco smoking, and severe psychiatric illnesses 2, 3, 4.
• The differential diagnosis of scurvy includes skin infections, hematologic disorders, collagen vascular disorders, and anticoagulant/antiplatelet side-effects 2.
• Pathognomonic skin findings, such as perifollicular bleedings and "corkscrew" hair, can help raise suspicion of scurvy 2.

Treatment and Prevention

• Vitamin C supplementation is a simple and rapidly effective treatment for scurvy, and it should be administered without hesitation in suspected cases 2, 3, 4.
• The required daily intake for vitamin C is ~60 mg, and this amount can be found in a medium-sized orange, making scurvy a rare disease in developed countries 2.
• However, scurvy can still occur in people with poor diet, malabsorption, or certain medical conditions, and healthcare personnel should be aware of its symptoms and treatment 2, 3, 4.

Reducing Unnecessary Vitamin Testing

• There has been an increase in unnecessary vitamin testing in general practice, causing increasing healthcare expenditures and medicalisation of patients 5.
• The most important factor hampering vitamin-test reduction programmes is the mismatch between patients and medical professionals regarding the presumed appropriate indications for testing for vitamins 5.
• Updating general practitioners' knowledge about test indications and their awareness of their own testing behaviour can be an important facilitator for vitamin-test reduction 5.