Normal Lab Values

Partial pressure of oxygen

75 - 100 mmHg

Partial pressure of CO2

38 - 42 mmHg

Arterial Blood pH

7.38-7.42

Oxygen saturation

94-100

Bicarbonate

22-28 mEq/L

Ammonia

15-50 µmol/L

-Levels are received from amino acid breakdown, gut bacteria that are digesting proteins in our food, and the breakdown of nucleic acids

-If ammonia levels increase, this is typically due to some liver dysfunction since the liver (cirrhosis, liver failure) is the detoxifying organ that converts ammonia to urea

Chloride

95-105 mmol/L

-Helps keep water normally distributed inside and out of the cell (this occurs mainly by working with sodium)

-Always stabilizes itself according to bicarb content. If there is lots of bicarb, there's typically little chloride, but if there is low bicarb, there's typically high chloride

------->Why? Well, consider emesis. When you vomit, you're releasing the contents of your stomach, HCl. This makes chloride levels go down, but increases bicarb content. Since there's more base in the body, your respiration rate will start to slow to increase CO2 (thus increasing blood acidity). So, the labs for someone who is vomiting should have a higher partial pressure of CO2, higher bicarb content, and lower chloride content.

------->Why? Well, consider diarrhea. Once entering the small intestine, chyme must be neutralized with bicarb to reduce its acidity. This means fecal content is more basic in nature. When one has multiple watery BMs, they're losing a lot of bicarb, which naturally increases chloride content to neutralize charges within the body. Increased chloride content also increases the acidity of the blood, which stimulates the individual to hyperventilate to lose more CO2, thus losing more acidity. In a person with diarrhea, you'd expect a lower partial pressure of CO2, low bicarb, and high chloride.

Copper

70-150 µgrams/dL

-Key part of many enzymes, like those found in the ETC in mitochondria, and in melanin production (hair and skin)

-Key player in a protein that oxidizes iron so that it can bind to transferrin in the bloodstream (without copper, iron cannot be mobilized properly and can lead to anemia even if there are enough iron stores in the body)

-Helps form bones and connective tissue

-Helps form myelin sheaths in the nervous system

**If there is defective copper excretion through the bile, then Wilson's disease can occur, where copper accumulates in the liver, kidneys, brain, and cornea, and may cause tissue damage.

Creatinine

0.8-1.3 mg/dL

-Waste product formed from creatine phosphate breakdown in the muscle (amount of creatinine is relatively proportional to muscle mass)

-Major indicator of kidney function. Creatinine levels determine the glomerular filtration rate. If creatinine is high, that means the kidneys are not filtering well

-Normally, creatinine will be low if you have low muscle mass or are malnourished

-Creatinine will be higher if you have higher muscle mass

Blood urea nitrogen

8-21 mg/dL

-Urea is created from protein and amino acid breakdown (ammonia) in the liver

-Urea is the major form of nitrogen waste in the body

-If BUN is high, that indicates decreased kidney function and possible dehydration

---->Sometimes the kidneys work fine, but because of dehydration, not enough BUN is being filtered out of the body

-If BUN is low, that indicates decreased liver function since the liver is the major detoxifier that converts ammonia to urea. In liver failure, we might expect ammonia levels to be high, but BUN to be low.

Ferritin

12-300 ng/mL (men), 12-150 ng/mL (women)

-Major indicator of iron levels in the body

-Ferritin is the storage protein for iron and is found mostly in the liver, spleen, bone marrow, and lymph, but also in the blood, which is how we measure ferritin levels

-Can be used as an early marker for iron deficiency anemia (if there's low ferritin, it likely means the patient has anemia)

-If ferritin levels are high, that could mean inflammation, infection, or cancer. In these situations, ferritin levels will be high even if iron is low, which means you have to be careful about detecting possible anemia (it will be harder to tell).

-If ferritin is extremely high, that could indicate iron overload syndrome, likely due to repeated blood transfusions as in sickle cell anemia, or in hereditary hemochromatosis, in which the gut absorbs too much iron from the diet and could cause cirrhosis (immense liver scar tissue), diabetes (due to iron deposition in the pancreas), and skin hyperpigmentation (bronze skin).

Glucose

65-110 mg/dL

-Important for fueling the cells, especially the brain and red blood cells, both of which depend mainly on glucose for energy

-Important for maintaining homeostasis (Too much glucose would result in increased insulin produced by beta cells. Too little glucose would result in increased glucagon production by alpha cells to increase blood glucose levels)

-Indicator of metabolic health (high glucose means hyperglycemia, which can also indicate diabetes) (low glucose means hypoglycemia, which can indicate high insulin production or liver disease)

-In instances like DKA, frequent urination can occur (the body needs to get rid of excess glucose, so it will urinate it out), and as a result, the individual feels severely dehydrated

-Hypoglycemia can cause neurological disorders, confusion, seizures

-Hyperglycemia can lead to atherosclerosis and subsequent hypertension

Inorganic phosphorus

2.5-4.5 mg/dL

-Important in bone and teeth health

-Key component in ATP and energy currency

-Important in cell structure (phospholipids)

-Important in the DNA and RNA backbones

-Low phosphate is typically due to malnutrition and alcoholism, and will cause muscle weakness, bone pain, confusion, impaired oxygen delivery

-High phosphate is typically due to kidney disease and tumor lysis syndrome, which can cause vascular calcification and bone/joint problems

Ionized calcium

1.03-1.23 mmol/L

-Regulates nerve conduction and contraction by binding to troponin

-Regulates cardiac function through cardiac action potentials and the plateau phase

-Important in blood clotting and clotting factors

-Will help with calcium deposition or mobilization in bone

-Low calcium: hypoparathyroidism, vitamin D deficiency, kidney failure, sepsis (could cause tetany, seizures, arrhythmia)

---->Why kidney failure? When there's a lack of calcium, PTH is stimulated, which increases calcium resorption from the bone, but also stimulates the kidney to reabsorb more calcium. If you top that off with a Vitamin D deficiency, which means very little calcium is being absorbed from the diet, then this places lots of strain on the kidneys

-High calcium: hyperparathyroidism, malignancy, excessive vitamin D intake (could cause fatigue, nausea, seizures, kidney stones)

---->Why kidney stones? When there's too much calcium, excess calcium will be excreted by the kidneys, leading to possible calcium deposits

Magnesium

1.7-2.2 mg/dL

-Works as an enzymatic cofactor for DNA synthesis, ATP production, and protein synthesis

-Helps regulate nerve impulses and muscle contraction

---->Low: muscle cramps, tremors

---->High: muscle weakness, diminished reflexes

-Cardiac rhythm stability

-Balances calcium and potassium levels

-Diuretics can cause low magnesium (urinating more magnesium), while renal failure can cause high magnesium due to decreased GFR and less magnesium excreted out

Phosphate

0.8-1.5 mmol/L

-Key component of ATP

-Bone and teeth formation

-Acts as a buffer in the blood to maintain pH balance (can bind with protons to reduce acidity)

-Component of DNA, RNA, and phospholipids

Potassium

3.5-5 mmol/L

-Maintains RMP for nerve impulses and muscle contractions to be conducted properly

-Neuromuscular function

-Low potassium: muscle weakness, cramps, paralysis, tachycardia

-High potassium: bradycardia, weakness, muscle twitching, paralysis

-Buffers pH (when acidic, K+ will move out of the cell, and when basic, K+ will move into the cell) --> this is because potassium is basic in nature

Pyruvate

300-900 µg/dL

-End product of glycolysis (will either go on to produce ATP under aerobic conditions, or lactic acid under anaerobic conditions)

-Precursor for glucose in the liver (gluconeogenesis), precursor for alanine in amino acid synthesis, and precursor for lipids (lipogenesis)

Sodium

135-145 mmol/L

-Primary extracellular cation regulating blood volume and osmolarity (hyponatremia will swell the cells, whereas hypernatremia will dehydrate the cells)

-Critical for generating APs in neurons and muscle cells

-Works with bicarb to buffer blood pH

-Hypernatremia can lead to high blood pressure (keeping water in), whereas hyponatremia can lead to low blood pressure

Total calcium

8.5-10.5 mg/dL

-Included ionized calcium, protein-bound calcium as in albumin (acts as a carrier for many substances in the liver, and prevents fluid from leaking out of blood vessels/edema), and complex calcium as in citrate, phosphate, and bicarbonate

***Albumin is often combined with diuretics to help edematous pts

Total iron-binding capacity

45-85 µmol/L

-Measures the maximum amount of iron that all transferrin in the blood can carry

-Transferrin carries iron from the absorption site in the intestine to the storage site in the liver (ferritin) and to other tissues (bone marrow, spleen)

-TIBC estimates transferrin availability indirectly

--->Low TIBC -->less transferrin to bind to iron or is saturated with iron (very common with iron overload or with chronic disease --> the body has too much iron leading to greater iron stores

--->High TIBC -->more transferrin to bind to iron (typically means there's an iron deficiency because the body is making more transferrin to pick up as much iron as possible) --> this means that more iron will be stored in ferritin

Total serum iron

65-180 µg/dL (men), 30-170 µg/dL (women)

-Tells us how much iron is circulating in the blood bound to transferrin

-Could indicate iron deficiency (low) or iron overload (high)

-Note that iron levels in the body could be fine (there could be a ton stored in the liver), but we would still have anemia if transferrin and TIBC levels were low

Transferrin

200-350 mg/dL

-Carries iron throughout the body

-Essentially has the same function as TIBC (check out the TIBC flashcard if there are questions)

Urea

Waste molecule of ammonia

-Measures the actual molecule circulating in the blood

-BUN measures the nitrogen content of urea in the blood (this is more commonly monitored here, but in other countries they monitor only urea)

-Both are important in determining kidney function, liver function, and hydration status

-Remember if BUN and urea is high, that indicates poor kidney function, but if they're low, that's indicative of liver dysfunction. This would mean that ammonia levels are also high.

Uric acid

0.18-0.48 mmol/L

-Derives from purine metabolism (DNA/RNA breakdown, nutritious foods)

-Uric acid is excreted mainly by the kidneys and is indicative of kidney health (high uric acid = poor GFR)

-High uric acid: gout (will crystallize in joints), kidney stones (uric acid forms in acidic urine), tumor lysis syndrome (increased DNA breakdown from cell death), metabolic syndrome (obesity, insulin resistance, hypertension)

-Low uric acid: seen in liver disease, SIADH (increased ADH leading to increased water retention), genetic defects

Zinc

70-100 µmol/L

-Required for DNA and RNA synthesis, cell growth, and repair

-Crucial for T-cell and antibody production

-Necessary for normal growth in children

-Important for keratinocyte and collagen synthesis

-Required for taste and smell

-Required for sperm production, testosterone synthesis, and ovulation

-Low zinc: malnutrition, diarrhea, liver disease, nephrotic syndrome (impaired immunity, hair loss, dermatitis, delayed growth)

-High zinc (rare): nausea, vomiting, anemia

Hemoglobin

13-17 g/dL in men and 12-15 g/dL in women

-Important in O2 and CO2 transport

-Will bind hydrogen ions to maintain blood pH

-Important level in CBC (complete blood count)

Hematocrit

0%-52% (men), 36%-47% (women)

-Indicates how much oxygen the blood can carry

-Low hematocrit means anemia, fatigue, and SOB

-High hematocrit means more oxygen potential but higher blood thickness

-Note that hematocrit can appear higher if dehydrated due to decreased plasma volume, and may appear lower if overhydrated due to increased plasma volume

-Important value in CBC

Mean Corpuscular Volume (MCV)

80-100 fL

-measure of the average size of RBCs

-If less than 80 fL, RBCs are smaller than normal, which could be due to iron-deficiency anemia, chronic disease, or thalassemia (less oxygen-carrying Hb)

-If over 100, RBCs are larger than normal, which could be caused by vitamin B12 deficiency (B12 and folate are both involved in DNA synthesis in rapidly multiplying cells like RBCs. When there is a deficiency, DNA synthesis will slow down, but the cytoplasm will continue to grow thus creating these large immature cells that don't typically reach max Hb capacity. This means that even with the larger cell, there's still not enough Hb), folate deficiency, alcoholism, liver disease, hypothyroidism, and certain meds

-Note that iron makes RBCs full, so if there is not enough iron, then the bone marrow cannot produce large amounts of hemoglobin, thus leading to a smaller, pale RBC.

-Both can lead to tachycardia to increase CO and pick up more oxygen. Over time, anemia can cause cardiac hypertrophy due to the rapid beating.

WBCs

4-10 * 10^9/L

-Encompasses neutrophils, lymphocytes, eosinophils, basophils, monocytes

-High values (leukocytosis) could indicate infection, inflammation, and stress

-Low values (leukopenia) can indicate bone marrow suppression, autoimmune disease, or severe infection

Bands

1 x 10^9/L

-Baby neutrophils in the blood that tend to accumulate when someone is fighting off an infection, sepsis, or severe inflammation

-If total WBC is normal, but bands is super high, this is still a sign of major infection

-Left shift: increased bands and other immature neutrophils are present (bone marrow is working overtime against infection)

Prothrombin time (PT)

11-14 sec

-How long it takes for blood to clot through common coagulation pathways in the body

-Note that Vitamin K is important in the activation of many clotting factors. Deficiency of Vitamin K can lead to prolonged clotting time, which increases the risk of bleeding

-PT is an important test for identifying vitamin K deficiencies (if there's a prolonged clotting time, it suggests this)

----> Lots of newborns receive Vitamin K at birth since this vitamin does not pass through the placenta that well, and the baby has not produced any gut bacteria yet to make the vitamin K. It's vital for allowing the baby's blood to clot if needed

-PT is also important in understanding liver function, since the liver is the organ that makes the clotting factors

Internalized Normalized Ratio (INR)

0.9-1.2

-These are standardized results of PT that allow for the results to be used across different labs.

-If you have a PT/INR > 1.2 it suggests that you have a prolonged clotting time which can lead to increased bleeding

-If you have a PT/INR <0.8-0.9 it suggests that you have decreased clotting time and is typically not that concerning unless it pairs with other abnormal tests

**PT/INR is typically important in monitoring patients on Warfarin/Coumadin: Since this drug is an anticoagulant that blocks Vitamin K recycling in the liver, we would expect PT/INR to be around 2.0-3.0 and higher (depending on the condition). We specifically use PT/INR for warfarin because it's more reflective of the extrinsic pathway (PTT is more reflective of the intrinsic pathway) of clotting using tissue factors, and some of the clotting factors in the extrinsic pathway are highly dependent on Vitamin K. Since Warfarin blocks Vitamin K recycling, we should see an increase in the PT/INR of patients on warfarin.

-In instances of extremely elevated INR but no bleeding, you would typically skip a dose or reduce the normal dosing value (or in super extreme elevation maybe give low-dose vitamin K to help activate the clotting factors)

-In instances of extremely elevated INR with active bleeding, you'd typically hold warfarin and get a Vitamin K drip going to reduce PT

Activated Partial Thromboplastin Time

20-40 sec

-PTT is more reflective of the intrinsic pathway of clotting, and if any of the clotting factors are dysfunctional, PTT will be prolonged

-Typically useful in identifying congenital (usurped at birth) disorders like Hemophilia A & B, which both indicate different clotting factor deficiencies, thus leading to a prolonged PTT

-Also used for monitoring heparin therapy (heparin specifically enhances antithrombin's effect on clotting factors in the intrinsic pathway

-If both PTT and PT are high, it indicates liver damage or something called Disseminated Intravascular Coagulation (Death Is Coming). This is a condition in which multiple microclots form in smaller vessels, thereby depleting a significant amount of clotting factors and platelets. Since the body is using up its stores for these small clots, it leaves the rest of the body vulnerable to bleeding (the patient is basically clotting and bleeding at the same time)

-If one or the other is high or low, it could indicate things like Vitamin K deficiencies, hemophilia, or warfarin/heparin drug regimens, depending on which clotting pathways are being intercepted.

Fibrinogen

1.8-4 g/L

-Also used to test clotting time since fibrinogen is an important protein involved in making the fibrin mesh of blood clotting

-Low fibrinogen is a bleeding risk, whereas high fibrinogen could be linked to thrombosis, followed by stroke and MI

Total Cholesterol

3-5.5 mmol/L

-High cholesterol is associated with a greater risk of atherosclerosis, stroke, and MI

-Indicative of lipid metabolism variabilities, like diabetes, liver/kidney disease, hypothyroidism

-Can be combined with High-density lipoprotein (HDL) and low-density lipoprotein (LDL) to determine overall cholesterol health

---->HDL is good cholesterol that helps to remove cholestrol from arteries

----->LDL is bad cholesterol that contributes to plaque buildup

Blood pH

7.35-7.45

Albumin

35-50 g/L

-contributes to colloid osmotic pressure

-keeps fluid inside blood vessels and stops it from leaking into the tissues

-acts as a transport protein for various substances (hormones, fatty acids, calcium)

-acts as a buffer for hydrogen ions (maintains pH balance)

-source of amino acids in malnutrition (AA breakdown for protein)

-Abnormal levels of albumin indicate nutritional status, liver damage, and renal damage

-Note that low albumin doesn't only cause edema but could lead to faster, stronger, and more toxic reaction

Alanine aminotransferase (ALT)

5-30 units/L

-Enzyme found mainly in the liver and will catalyze the conversion of alanine to pyruvate

-If higher than normal, it could indicate liver injury

-If mildly elevated, it could indicate fatty liver (high-fat diet leads to increased fat content in the hepatocytes of the liver, which stresses the cell, wears down the membrane, and causes apoptosis, thus leaking a ton of ALT out into the blood) medications (acetaminophen in high amounts can be dangerous for the liver as it overwhelms detox pathways and causes hepatic necrosis) and alcohol use (alcohol metabolism in the liver creates a very toxic substance that when accumulated in high amounts can cause cell damage and death thus leading to an increase in both ALT and AST)

-Very high levels could indicate acute viral hepatitis

Aspartate Aminotransferase (AST)

5-30 U/L

-Enzyme involved in A.A metabolism

-Unlike ALT, it's found in other tissues besides the liver, like the heart and muscle (plus RBCs)

-This means that MI, Rhabdomyolysis (muscle breakdown), and hemolysis (RBC breakdown), leads to increased AST

-AST levels typically increase in relation to alcohol liver disease, whereas ALT would increase in relation to nonalcoholic liver disease

Creatine Kinase (CK)

25-200 U/L

-Plays an important role in energy metabolism and is a biomarker for muscle energy, cardiac events like MI, drug-induced myopathy, etc

**CKMB relates to creatine kinase in the cardiac muscle

Troponin

0-0.4 ng/mL

A regulatory protein complex in skeletal and cardiac muscle cells that controls muscle contraction

-If heart muscle cells are damaged, troponin is released

-High levels of troponin in the blood can indicate MI, myocarditis (inflammation of the heart muscle due to an attack by the immune system if there's an infection)

-Can also detect sepsis, PE, renal failure, and heart failure

-Note that troponin is much more specific to the heart whereas CK could also indicate skeletal damage

Vitamin B12

130-700 ng/L

-Essential for rapidly dividing cells (like the bone marrow)

-Needed for normal maturation of RBCs

-Required for myelin synthesis creation (deficiency could lead to tingling, numbness, balance issues, etc

Angiotensin Converting Enzyme

23-57 U/L

-Converts angiotensin 1 to 2, which raises BP through vasoconstriction and increased sodium and water retention

-Will also degrade bradykinin (a vasodilator), which will lead to increased vasoconstriction

-Overly high ACE will lead to chronic hypertension, vascular damage, and heart strain

C-Reactive Protein

< 5 mg/L

-A protein made by the liver that increases in the blood whenever there is inflammation, infection, or tissue energy

-Will fall once inflammation dies back down

-Great lab for monitoring treatment response

D-Dimer

< 500 ng/mL

-A fragment is formed when a blood clot is broken down by fibrolysis

-Detects clot formation plus breakdown

-Used to rule out DVT, PE

-If D-dimer increases, it can indicate worsening clot breakdown

Erythrocyte sedimentation rate (ESR)

Less than age/2 mm/hour

-A simple, inexpensive blood test that measures how quickly RBCs sink to the bottom of the test tube

-Inflammation causes the RBCs to become stickier, thus becoming denser and sinking to the bottom of the test tube quickly

-Can help track progression of disease

-While ESR is better for tracking chronic trends, CRP is better for tracking acute changes