Can ferritin levels be low in dehydration?

Ferritin Levels in Dehydration

Ferritin levels are not typically low in dehydration; in fact, dehydration can lead to hemoconcentration which may falsely elevate ferritin levels. 1

Relationship Between Dehydration and Ferritin

Dehydration affects laboratory values through hemoconcentration, which can impact the interpretation of various biomarkers including ferritin:

• When dehydrated, the concentration of blood components increases due to reduced plasma volume
• This concentration effect can cause ferritin levels to appear falsely elevated, not lowered
• Ferritin is primarily a marker of iron stores and an acute phase reactant, not directly affected by hydration status 1

Factors That Actually Lower Ferritin

Ferritin is typically lowered by:

1. Iron deficiency - The most common cause of low ferritin

   • A ferritin level <15 μg/L is highly specific (99%) for iron deficiency 1
   • In the absence of inflammation, a level <45 μg/L is considered the optimal diagnostic cutoff for iron deficiency 1

2. Blood loss - Chronic or acute bleeding can deplete iron stores

   • In men and postmenopausal women, iron deficiency should prompt investigation for underlying causes, particularly gastrointestinal sources 1

3. Malabsorption - Conditions affecting iron absorption

   • Celiac disease, inflammatory bowel disease, and other malabsorptive conditions 1

Factors That Elevate Ferritin

Ferritin can be elevated by:

1. Inflammation - Ferritin is an acute phase reactant

   • With inflammation (elevated CRP), a ferritin level <100 μg/L may still indicate iron deficiency 1
   • Inflammatory conditions can mask underlying iron deficiency 2

2. Liver disease - Hepatocellular damage releases stored ferritin

3. Malignancy - Can cause elevated ferritin levels

4. Infection - Part of the acute phase response

5. Dehydration - Through hemoconcentration effect 3

Clinical Implications

When interpreting ferritin levels:

• Always consider hydration status when interpreting ferritin results
• In dehydrated patients, recheck ferritin after rehydration for more accurate assessment
• Consider measuring additional markers of iron status such as transferrin saturation, especially when inflammation is present 1
• In patients with chronic kidney disease, ferritin can be particularly misleading due to inflammation 4

Common Pitfalls in Ferritin Interpretation

• Failing to consider hydration status when interpreting laboratory values
• Not accounting for inflammation when interpreting ferritin (check CRP when in doubt)
• Using inappropriate cutoff values for different patient populations
• Relying solely on ferritin without considering clinical context and other iron markers

In conclusion, dehydration does not lower ferritin levels but may actually cause falsely elevated values due to hemoconcentration. When evaluating iron status in a dehydrated patient, ensure proper hydration before drawing definitive conclusions from ferritin levels.