'Normal' Lab Values Don't Equal a Healthy Patient
Normal lab values aren't necessarily optimal for health. Have you ever gone to the doctor because you weren't feeling well -- only to have all the labwork come back normal? Have you treated a patient whose status declined, but his blood work showed nothing unusual?
Abnormal lab values represent the levels at which many patients will be symptomatic. However, patients can also have physical symptoms when clinical signs, such as lab values, are unremarkable. When this occurs, the doctor may discount the symptoms or render a diagnosis that includes the word "subclinical." Here are a few examples of lab values that appear normal even while patients are symptomatic.
Some researchers suggest that under-diagnosis of subclinical vitamin B12 deficiency in the U.S. explains our country's high Alzheimer's disease rate. In addition to decreased mental functioning, low vitamin B12 can cause fatigue, lightheadedness, paleness, sore tongue, easy bleeding, weight loss, GI symptoms and depression. Patients are commonly symptomatic with vitamin B12 values at the low end of what American labs deem normal (>200 pg/mL). Some doctors suggest a minimum value of 350 pg/mL is necessary for patients to be asymptomatic. Japan and some European countries set the bar even higher, with the lower limit of 500-550 pg/mL.
Like vitamin B12, normal thyroid hormone levels can be present in subclinical hypothyroidism. Primary care providers, who commonly sort out thyroid issues, are often ignorant of thyroid intricacies, leading patients to have to take charge and direct their own medical care.
Healthcare providers may also fail patients in the area of hair loss. The body considers hair growth a non-essential function, so it only provides nutrients to the hair after all other systems have been adequately nourished. Significant hair loss can occur with "normal" lab values. Serum ferritin is among labs that are used to evaluate possible medical causes of hair loss. "Normal" serum ferritin value is 20-300 ng/mL, but hair growth requires serum ferritin to maintain at a minimum of 70 ng/mL.
Here's a personal account. After months of extreme fatigue but normal hemoglobin and hematocrit levels, the doctor finally drew an anemia profile and sent me to a specialist. My serum ferritin level was 7 ng/mL. When that level doubled but my fatigue didn't change, the hematologist suggested the issue was vitamin B12, which had lowered to 284 pg/mL. Once my B12 jumped to >1000 pg/mL and my ferritin to 36 ng/mL, the hematologist informed me my levels were normal, discharged me and instructed me to wean off supplements.
While I wasn't ready for bed at 2 p.m., I didn't feel much better. Repeat bloodwork revealed normal values, so I just kept trudging along. Now I realize normal doesn't mean optimal. My serum ferritin level has been 70 ng/mL only once in the last three years, yet my doctor has considered that more than sufficient to forego supplementation. Vitamin D is another important level for hair growth. In July 2011, my Vitamin D was low, but not low enough to treat. In March 2012, my Vitamin D was nearly nonexistent and I was prescribed supplements. After one normal lab result in June 2012, my physician was content and refused my request for a repeat level to make sure it was maintaining. After losing, conservatively, one-third of my hair in the last year, I finally consulted a dermatologist specializing in hair loss who informed me retesting is crucial. (Yes, I'm changing primary care physicians).
Unknowledgeable physicians may overlook important symptoms and clinical signs. Worse, they may refuse to look beyond normal test results for answers. If you or your patients don't feel well, don't assume any doctor's interpretation of "normal" lab values is meaningful. "Normal" does not equal "optimal." Trust your instincts. Seek a second opinion.