How it works and what you need to know.
Blood tests (aka blood work) can show us, obviously, what’s in our blood. (And, by extension, what’s in our bodies). That’s because blood gives us insight into what we can’t see from the outside.
In this article we outline how it works and what you need to know.
What is blood work?
Blood is a transport system for the body. We carry all kinds of things in the approximately 5 litres of blood that circulates constantly through our system.
Blood tests, aka blood work, can show us what’s in our blood — and by extension, what’s in our bodies. Blood can also show us changes in our bodies that we might not be able to see from the outside — such as our blood sugar levels or nutritional status.
Thus, we can use blood work to assess overall health, and it can give us a much more accurate and objective snapshot of wellness than “Gee, I think I had some veggies yesterday” or “I feel fat today”.
How is blood work done?
We get blood for testing from:
>Capillary skin puncture (finger stick)
>Dried blood samples
>Blood drawn from an artery
>Blood drawn from a vein (most common)
>Bone marrow aspiration
What happens to blood after it’s drawn?
Blood is analyzed in a lab. The blood is put into a centrifuge and spun until it separates.
Then, technicians compare results to a “reference range.” The reference range is the range of expected values for each test listed.
Expected ranges used in lab analyses include 95% of the “healthy” population. So, 95% of healthy people would have lab values within these ranges. This range varies depending on the lab, region (e.g. US vs EU) and type of blood component.
A number above or below this reference range can give valuable diagnostic information about body systems. High and low values are especially useful when taken in context with other symptoms, lifestyle factors, and tests.
Variation in results and ranges
Lab values vary for each person and must be assessed relative to other factors. While reference ranges are established after testing a large number of healthy people, everyone is slightly different.
Blood analyses vary based on:
>Time of year
Blood work: the tests
The basic test
A general lab ordered by a physician is typically called SMAC-20, SMA-20, or Chem-20.
This basic test looks at 20 different parts of the blood including levels of certain minerals, proteins, etc. This test is standard and should be done, although it’s not very telling of one’s overall health profile.
Beyond the basic SMAC-20, there are many different blood tests you can request. Highlighted below are some of the most useful tests.
Test What it is Higher with Lower with
1.Total cholesterol Cholesterol is necessary for building brain and nerve cells, along with various hormones.Too much of it floating around the blood is associated with cardiovascular disease (CVD). Some experts claim that if you keep this under 150 mg/dL – you’ll be “heart attack resistant.” Cholestasis, nephritic syndrome, chronic renal failure, hypothyroidism, alcoholism, a diet high in cholesterol and fat, obesity, pregnancy. Myeloproliferative disease (e.g., polycythemia vera, thrombocytosis, myelofibrosis, chronic myelogenous leukemia), hyperthyroidism, malnutrition, some lung diseases, warmer months, sitting (versus standing), certain drugs, estrogen medications.
2. Low density lipoprotein (LDL) This compound carries cholesterol to body cells from the liver. Small, dense LDL levels have a strong association to CVD. Overeating (and most folks overeat processed fats, sugars, and refined grains), hypothyroidism, nephrotic syndrome, multiple myeloma, hepatic obstruction, anorexia nervosa, diabetes, renal failure, porphyria, pregnancy, androgen use. Tangier disease, hyperthyroidism, anemia, Reye’s syndrome, inflammatory joint disease, estrogen use.
3. Apoplipoprotein A & B These are surface proteins of lipoprotein particles. Apo A is the main component of HDL. Apo B is the main component of LDL. Apo A: Not significant.Apo B: Diabetes, hypothyroidism, renal failure, hepatic disease, Cushing’s syndrome. Apo A: Diabetes, renal failure, diets very high in polyunsaturated fat, smoking, some drugs, genetic diseases.Apo B: Malnutrition, plant-based diets, high polyunsaturated fat diets, some drugs, genetic diseases.
4. Lipoprotein (a) (Lp(a)) This is another sub-fraction of cholesterol. High levels of this are associated with premature heart disease. Post-menopausal women, African-American race, renal failure/disease, estrogen depletion, hypothyroidism, diabetes. Not significant – levels might be slightly lower with niacin use.
5. High density lipoprotein (HDL) This compound carries cholesterol from cells back to the liver. There is a strong relationship between HDL and CVD. The ratio of total cholesterol to HDL is considered a better predictor of heart disease than total cholesterol or LDL. The goal is to have a ratio of 5:1 or lower in men; 4.4:1 in women. An optimum ratio is 3.5:1 or lower in men, 3.4:1 or lower in women. Lots of exercise for many years, estrogen use, low levels of alcohol consumption. Diabetes, cholestasis, renal failure, obesity, sedentary behavior, certain drugs, insulin resistance.
6. Triglycerides Fat in the blood levels predict the body’s ability to metabolize fat. When triglycerides are under 100, the LDL calculation is usually inflated. The triglyceride to HDL ratio might be the single best predictor of heart disease risk. A ratio above 4:1 is cause for concern. The goal is a ratio of 2:1; the lower the better. CVD, liver disease, alcoholism, renal disease, hypothyroidism, pregnancy, birth control medications, smoking, obesity, diabetes, gout, anorexia nervosa, a recent meal with fat. Malnutrition, hyperthyroidism, some lung diseases, strenuous exercise, a lean body.
7. C-reactive protein (CRP) A marker for low grade inflammation. Useful in predicting CVD. Pain, fever, infection, inflammatory bowel disease, arthritis, autoimmune disease. Not significant – can be an indication that inflammation is decreasing.
8. Homocysteine An amino acid found in small amounts in the blood resulting from the synthesis of cysteine from methionine. Only cleared from the body with adequate blood levels of vitamin B12, B6 and folate. Elevations of homocysteine are associated with CVD. Folic acid deficiency, vitamin B12 deficiency, vitamin B6 deficiency, heredity, older age, kidney disease, male gender, certain medications. Not significant.
Liver function tests
Test What it is Higher with Lower with
1. Alkaline phosphatase
If the bile duct is blocked (cholestasis), this enzyme gets backed up and spills into the bloodstream. Values can help to evaluate bone health since elevated levels show active bone growth or inflammation due to damaged or healing bones. If elevated in conjunction with GGT, we have a liver issue. Younger age, fatty liver, pregnancy, obstructive jaundice, liver disease, diabetes, alcohol consumption, eating a fatty meal, gallbladder conditions, bone growth, damaged bones, Paget’s disease, vitamin D deficiency. Not significant. May indicate celiac disease, malnutrition, scurvy, or magnesium/zinc deficiency.
2. GGT A cholestatic liver enzyme. If the bile duct is blocked (cholestasis), this enzyme gets backed up and spills into the blood stream. Evaluates liver and gallbladder function, but is also found in kidneys. Helpful when alkaline phosphatase levels are elevated. High alcohol intake, various liver disorders, stress, excess body fat, exercise, some drugs.If GGT and alkaline phosphatase are elevated, it’s likely a liver disorder. If GGT is low and alkaline phophatase is elevated, it’s likely a bone disorder (instead of a liver disorder). Otherwise, low GGT isn’t significant.
3. AST/SGOT An enzyme found mainly in the liver, heart, and muscles – organs with high metabolic activity. Liver damage, heart damage, muscle damage, high body fat, diabetes, mononucleosis, pregnancy, hypothyroidism, shock, some drugs. Azotemia, dialysis, vitamin B6 deficiency.
4. ALT/SGPT Enzyme found mainly in the liver. Damage to the liver from alcohol, inflammation, increased body fat, mononucleosis, some drugs, heart attack, aspirin, strenuous exercise. Not significant.
5. Bilirubin This is a normal, yellow fluid metabolic by-product of red blood cell breakdown that must be cleared by the liver. Bile flow impairment, carcinoma, liver disease, high levels of red blood cell breakdown, prolonged fasting, anorexia nervosa, niacin supplementation, some forms of anemia.Note: Exposing a blood sample to 1 hour of sunlight can decrease bilirubin. Rare and not significant.Note: Foods with lots of orange color (carrots, yams) can increase the yellow hue in serum and falsely increase bilirubin levels if tested with a spectrophotometer.
6. Ammonia The end product of protein metabolism. The liver normally removes ammonia via portal vein circulation with conversion to urea. Levels in our blood dramatically influence acid/base balance and brain function. Reye’s syndrome, liver disease, gut hemorrhage, renal disease, inborn errors of metabolism, excessive protein intake, some drugs, intense exercise, smoking, alcohol, constipation, gut infection. Not significant.
Kidney function tests
Test What it is Higher with Lower with
1. Creatinine This is a metabolic by-product of muscle metabolism that must be filtered by the kidneys. Since muscle creatine breaks down into creatinine, someone with more muscle will have abundant creatine and potentially higher creatinine levels. When there is disordered kidney function, the ability to excrete creatinine diminishes. Impaired kidney function (along with high BUN), obstruction of the urinary tract, muscle disease, shock, heart failure, dehydration, rhabdomyolysis, high meat diet, hyperthyroidism. Decreased muscle mass, inadequate protein intake, pregnancy. Low levels usually aren’t cause for concern.
2. BUN (blood urea nitrogen) Urea is a waste product of protein metabolism eliminated from the body through urine, feces, and perspiration. BUN is a measure for kidney function because if filtration in the kidneys can’t keep up with elimination, kidney function is likely diminished. Various kidney diseases, heart failure, urinary tract obstruction, gut hemorrhage, diabetes with ketoacidosis, steroid use, circulatory disorders, high animal protein intake, intense exercise, salt or water depletion from sweating, diarrhea, vomiting. Pregnancy, liver failure, acromegaly, Celiac disease, syndrome of inappropriate antidiuretic hormone (SIADH), malnutrition.
3. Creatinine/BUN ratio This provides more information about potential kidney problems. Increased ratio with normal creatinine occurs in: Salt depletion, dehydration, heart failure, catabolic states, gut hemorrhage, high animal protein intake.Increased ratio with elevated creatinine occurs in: Obstruction of the urinary tract, ketoacidosis, prerenal azotemia. Decreased ratio with decreased BUN occurs in: Tubular necrosis, malnutrition, dialysis, SIADH, pregnancy.Decreased ratio with elevated creatinine occurs in: Some drug use, rhabdomyolysis, muscular folks who are developing kidney failure.
Reproductive function tests
Carbohydrate tolerance tests
Protein status tests
Vitamin, mineral, acid/base status tests
White blood cell tests
Red blood cell tests
Mishaps with blood draws
If blood is drawn from your arm after the tourniquet is on for several minutes, values can be skewed because cells will concentrate in the lower arm.
If the needle used is too small, it can cause red blood cells to break, leading to a skewed analysis.
If the puncture site isn’t sanitized – infection can result.
If you tense up excessively during a blood draw, you can experience extensive bruising at the site.
Summary and recommendations
Getting annual blood work with a physician is a good idea for preventative health. This way you can observe trends and catch potential health problems before they spiral out of control.
Note: If you want to track your health trends over time, make sure to request a copy of your lab results and keep them in a file somewhere.
Also note: If you’re willing to pay for your own blood tests, or you doctor won’t order lab tests for you on a regular basis, check out the Wellness Complete panel by EXOS. It’s the most comprehensive health and wellness panel we’ve found.
Eat, move, and live… better.
Yep, we know… the health and fitness world can sometimes be a confusing place. But it doesn’t have to be.