Vitamins can throw off lab tests

Published: Thursday, August 1, 2002 at 6:01 a.m.
Last Modified: Thursday, August 1, 2002 at 12:00 a.m.
Q:I feel perfectly healthy, but my latest physical showed an abnormal thyroid lab test. I take a handful of vitamins, no drugs, and I don't want to start any now.
My doctor wants me to begin prescription thyroid hormone. Should I get a second opinion?
K.S., Pueblo, Colo. A:That's up to you, but before you get a second opinion, you may want to repeat the lab work minus the "handful of vitamins."
Many natural, over-the-counter supplements can affect lab work related to numerous functions, including your thyroid gland.
Natural estrogens like soy can elevate thyroid stimulating hormone. Tyrosine, an ordinary amino acid, happens to be a thyroxine precursor, meaning it could lower a person's TSH. Tyrosine is taken for many conditions, including depression; it's found in protein shakes.
Other problematic supplements include biotin, kelp and bladderwrack. You don't have to stop taking these; you just need to know that they may throw off otherwise normal thyroid lab tests. This is important information because the last thing you want to do is take medicine for a condition that does not truly exist.
Why don't you go on a vitamin holiday? Stop taking everything for a week, then retake your lab tests.
n n n Q:I take a diuretic, furosemide (Lasix), for my high blood pressure, but now my potassium is also low. Before I begin a prescription dose of potassium, I was wondering if certain foods might help my situation. I'll eat anything.
L.L., Chicago A:Diuretics are designed to eliminate fluid and take pressure off the heart and blood vessels. Removal of fluid from the body upsets the ratio of potassium to water, which is why many people have to take a potassium supplement when they're on diuretics.
If you want, you can eat more bananas, avocados, peaches, sunflower seeds, lima beans, spinach, broccoli, cantaloupe and nuts.
n n n Q:I'm taking my baby aspirin every day. Don't think me silly or anything, but tell me why is it 81mg and not just 80 mg.
All right, so I'm slightly compulsive, but wouldn't it just be simpler to round it to 80 mg or does that 1 mg really make a difference?
G.D., Hollywood, Fla. A:The 1 mg makes no difference clinically; it's a question of convenience.
The makers of aspirin take the standard 325 milligram dose and divide it by four in order to determine the "baby" dose of 81mg. For you apothecary wizards, this is the equivalent of one and a quarter grain.
Now if you do the math, and I know you will, you'll see that a 325mg pill divided by four equals 81.25 mg. Don't ask me where the 0.25 went; even the representatives of this wonder pill don't know. Companies round it off to 81mg so thinking consumers won't be puzzled. So much for that.
This information is not intended to treat, cure or diagnose your condition. Always consult your physician. Suzy Cohen is a registered pharmacist. Write to Dear Pharmacist, c/o The Gainesville Sun, PO Box 147147, Gainesville, FL 32614-7147; or e-mail; or visit www.dearpharmacist

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