What is “Vitamin D”

What is Vitamin D

Vitamin D has received a lot of attention over the past decades, because of the extensive health-related research that has been published on it. Vitamin D, also called the sunshine vitamin, is a fat-soluble vitamin that is produced mainly when the skin comes into contact with the sun’s UV radiation. There are approximately 2,700 binding sites for vitamin D in the human genome (DNA), which suggests that vitamin D exerts influence on various nearby genes associated with autoimmune diseases.

There are two main forms of vitamin D that are taken from food or supplements –ergocalciferol, also known as D2, and cholecalciferol, or D3. Vitamin D3 is converted into 25-hydroxycholecalciferol in the body, and then 1,25-dihydroxyvitamin D (calcitriol) in the kidneys. Calcitriol is the most potent and active steroid form of vitamin D3, but is generally not measured unless an individual has kidney disease or if there is reason to believe the body is not converting the vitamin into its active form.

Vitamin D plays an important role in the absorption of calcium from the intestines and is vital to bone strength. Measured in nanograms per milliliter (ng/mL), adult ranges of vitamin D may be found in the table below. Reference ranges for high and low values may vary according to the lab, so be sure to look at the ranges provided on your blood test form. Although getting vitamin D count on a routine blood test is becoming more popular, not all doctors request it. Make sure to ask your doctor to include this marker when you get your blood drawn.

25 Hydroxy D
Deficient Optimal Excess
<40 ng/mL 40 – 60 ng/mL 60 + ng/mL

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What is Progesterone?

progesteroneAlthough progesterone is found in both males and females, it is primarily known for its role in conception, pregnancy, and the regulation of a woman’s menstrual cycle. Produced in the ovaries, adrenal glands, and the placenta of pregnant women, progesterone has several functions in addition to its role as a sex hormone. It supports bone density, protects against the proliferation of breast and uterine cells, and acts as a coating for the nerve fibers of the brain, reducing hyperexcitability. A female’s progesterone levels rise and fall according to the stages of her life. While men also synthesize a small amount of this hormone, it is much less important than testosterone when it comes to sexual maturity. Synthetic forms of progesterone (progestins) are widely used in birth control pills and hormone replacement therapy.

Natural progesterone levels are suppressed in women who take synthetic forms, so blood tests are inaccurate in these case. Otherwise, a blood test is usually administered twenty-one days after the start of a woman’s period, if she is still menstruating. Because progesterone readings normally fluctuate in women, there are a number of normal ranges for this hormone, as shown here:

Follicular phase 0.2-1.4 0.64 – 4.45
Luteal phase 4 – 25 12.7 – 79.5
Post-Menopausal 0.1 – 1 0.32 – 3.18
Males 0.1 – 1 0.32 – 3.18
Conversion factor: 1 ng/ml = 3.18 nmol/l

While variations in progesterone levels may be perfectly normal, sometimes a high reading is cause for further testing.

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How to prepare for a blood test

It’s best to ask the lab or your doctor before going for testing to make sure that there are no special requirements for preparation for the tests you have scheduled, and if there are specific requirements, to adhere to these carefully to avoid invalid test results and waste your time and money. Most tests do not require special preparation, but check it out before arriving at the test location.


For cholesterol and glucose tests, you must fast for at least 8 hours prior to having your blood drawn, unless your doctor tells you otherwise. Fasting means no eating or drinking for at least 8 hours before the test, except water. After your blood is drawn, you may resume your regular diet. Most blood lab tests that don’t mention “fasting” in their names do not require any special preparation. However, a few tests, like the Fasting Blood Sugar and the Glucose Tolerance (which does not mentioned “fasting” in the title) do require special preparation and the lab will provide that information at your request prior to your arrival for testing. Some panels, such as Cardiac Risk include a test (e.g., Apo A and B, triglycerides) that should be done on a fasting specimen, often this is mistakenly or overlooked.


Drink plenty of water before your blood test. This helps keep your blood pressure from dropping. The leading cause of fainting during a blood test is a drop in blood pressure. Avoid coffee or other caffeinated drinks before your test because they actually cause your body to expel water.


Unless fasting is required for your testing, eat breakfast to help keep your blood sugar up. This will help you feel better after your blood draw and prevent lightheadedness and dizziness. If you think you might be nauseous during the blood draw don’t eat immediately before your appointment.


If you take a blood-thinning medication, such as heparin or Coumadin (warfarin), tell the phlebotomist about these medications before your blood is drawn. After your blood is drawn, the phlebotomist will closely observe the puncture site to see that bleeding has stopped before you leave the collection location.


If you are anxious about what is going to take place, ask the person taking your blood to explain everything he or she is doing. Or think of something entirely different, like your vacation or what you are going to do after your blood test.


Eat a snack after you have your blood drawn. Take a snack with you if you will not be going directly back home or to work. That way you can eat it directly after the blood draw.

Here are a few tests with special preparation rules:

Stool examination for Occult Blood does require quite a rigorous adherence to diet for several days before and during collection of the specimen. False-positives may be the result of failure to observe these instructions, and the consequences involve extensive follow-up testing which can be as expensive as they might be unpleasant.

Sputum Cytology (sputum=mucus) specimens are best collected after deep coughing early in the morning because the richest accumulation of cells of diagnostic quality is to be found in this type of sputum sample.

Semen analysis must be performed on a clean, fresh, warm specimen, best collected at the laboratory facility.

Vitamin B12 blood specimens require testing after refraining from taking multivitamins for at least a week and may only be valid when a specimen is collected several weeks after the last B12 injection.

Remember, it is always wise to contact the doctor, lab rep or receptionist at the lab of your choice beforehand to be certain that there are no special preparations you need to undertake before going to the lab for any testing.

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Thyroid Hormones

What are “Thyroid Hormones”?

Located in the neck, the thyroid gland produces hormones that control metabolism and energy production. These hormones regulate how each cell converts food into calories and utilizes stored fats to create energy. They influence weight control, nerve and gastrointestinal health, nutrient absorption, and energy use. Initiated by thyroid-stimulating hormone (TSH) from the pituitary gland, thyroid hormone production includes two principal types: the active hormone triiodothyronine (T3) and the inactive hormone thyroxine (T4), which is converted to T3. In addition to TSH count, thyroid hormone measurements can include levels of total T3 and T4, and free T3 and T4. Free levels refer to the amount of circulating hormone available for use by your cell, while total levels also include the amount of hormone bound to proteins. Typically, free T3 and T4 readings are considered more reliable indicators of thyroid disturbances than total readings.

Thyroid Test Reference Range
TSH (Thyroid Stimulating Hormone) 0.5-4.70 mIU/L
Total T4 (Thyroxine) 4.5-12.5 mIU/L
Free T4 (Free Thyroxine) 0.8-1.8 mIU/L
Total T3 (Triiodothyronine) 80 -200 mIU/L
Free T3 (Free Triiodothyronine) 2.3- 4.2 mIU/L

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What is “Cortisol”?

Made in the adrenal glands, cortisol is a steroid hormone that increases blood sugar, suppresses the immune system, fights inflammation, decreases bone formation, and helps metabolize fat, protein, and carbohydrates when it is released in appropriate amounts. It is most commonly known as the “stress hormone,” as it is released in response to both physical and psychological stress. While this reaction is normal and healthy in short bursts, chronic stress leads to the creation of too much cortisol, which results in a variety of imbalances in the body. If cortisol is chronically elevated, it can block the growth of nerve cells in the brain and damage the brain’s memory center (hippocampus), which may begin to shrink when high cortisol and low DHEA occur together.

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What is “DHEA”?

What is DHEA? It stands for Dehydroepiandrosterone and is a building block of steroid hormones that is produced predominantly in the adrenal glands. It serves as a precursor to the sex hormone testosterone and estrogen in both men and women. DHEA is also a building block of the stress hormone cortisol and supports immune system function. DHEA may also increase insulin sensitivity, enhance fat metabolism, and act as an antioxidant. There are two type of dehydroepiandrosterone: DHEA and its sulfate form, dehydroepiandrosterone sulfate (DHEAS). Because DHEAS remains in the bloodstream longer than DHEA, doctors generally test DHEAS numbers when they suspect a problem with this hormone. Typically, DHEAS levels are high in newborns and drop significantly after birth. They increase during puberty, peak soon after, and decline with age.

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What are white blood cells?

What are ‘White Blood Cells’?

White blood cells (WBCs), also known as leukocytes, are an essential component  of the immune system, serving to protect the body from harmful microorganisms.

When an infection develops in the body, the number of white blood cells quickly increases, and the cells are transported to the infection site to attack and destroy the bacteria, virus, or other “bug” causing it.

There are five types of white blood cells that circulate in the blood:

types of white blood cells wbc

White Blood Cell Types – HealthMatters.io (copyright)

The concentrations of each can fluctuate on a day-to-day basis. Each type has a specific role and function. For more information on the individual types, check out these links:

Measuring the number of the different white blood cells in the body is useful for diagnosing infections and other diseases. This blood test is called white blood cell differential test, and it calculates the number of each WBC type as well as the total WBC count.

All white blood cells are measured in micrograms per liter (mcg/L)

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