Alanine aminotransferase (ALT)

ALT is a liver enzyme test measuring hepatocellular damage. It can often be elevated in metabolic syndrome and obesity, due to non-alcoholic fatty liver disease (NAFLD.)

When to check

Baseline. If the baseline result is abnormal, repeat every 6 months.

Standard reference ranges
Women: 10-25 IU/L
Men: 10-33 IU/L
Women: 0,25-0,60 µkat/L
Men: 0,25-0,75 µkat/L
 

Low-carb considerations

Elevated ALT due to metabolic syndrome or NAFLD tends to improve on a low carb, at least longer term.

Occasionally, ALT might increase during the initial three months on low carb, coinciding with weight loss. Once the weight loss is over, this elevation tends to disappear and ALT usually normalizes.

 

Elevated levels

Higher than normal values may be caused by:

  • NAFLD (most commonly), or liver cirrhosis
  • High alcohol consumption
  • Drug side effects, e.g. statins, aspirin, some sleep aids
  • Mononucleosis

Extremely high values may be caused by:

  • Acute viral hepatitis
  • Overdose of drugs like acetaminophen (Tylenol)
  • Liver cancer

 

More

ALT is found in serum and in various body tissues, but is primarily associated with the liver. It is commonly measured as part of a diagnostic liver function test to determine liver health. The transaminases (ALT and AST) are the most sensitive tests of hepatocellular damage but are not very specific. Since many patients with NAFLD have normal ALT levels, an abdominal ultrasound is recommended to diagnose NAFLD.

 

Fasting glucose

Fasting blood glucose (FBG)is most commonly used to diagnose or assess diabetes, monitor hyperglycemia and hypoglycemia, and aid in diabetes treatment decisions.

When to check

Baseline and annually.

Standard reference ranges
Average diet: 65 – 100 mg/dL
On low carb: 54 – 100 mg/dL (or higher, see below)
3.8 – 5.5 mmol/L
On low carb: 3.0 – 5.5 mmol/L (or higher, see below)

 

Elevated levels

Higher than normal values may be caused by:

  • Type 1 or type 2 diabetes
  • Acromegaly
  • Acute/chronic pancreatitis
  • Cushing’s syndrome
  • Arug side effects: glucocorticoids
  • Pheochromocytoma
  • Stress

 

Decreased levels

Lower than normal values may be caused by:

  • Adrenal insufficiency
  • Alcohol consumption
  • Exogenous insulin
  • Hypopituitarism
  • Hypothyroidism
  • Insulinoma
  • Malignancy
  • Malnutrition
  • Drug side effects, e.g oral hypoglycemic agents
  • Sepsis

 

Low-carb considerations

Patients eating low carb may have much lower FBG levels than patients following the traditional food pyramid. Standard reference ranges reflect a society of carb-burners, not fat-burners. Once a low carb patient transitions into a fat-burner, they will have a lower demand for glucose to maintain normal body function. FBG levels may consistently lie between 3.0 to 3.9 mmol/L or 54 to 70 mg/dL once the patient has been following low-carb for several months.

However, FBG numbers can also go up on low carb, which can surprise patients and doctors alike. This common occurrence is the “dawn phenomenon” and reflects that muscles are in “glucose refusal mode” — or what some low carb doctors have dubbed “adaptive glucose sparing.” Generally, this is not a concern as the rest of the day blood glucose will remain low. The FBG may be the highest value of the day.

 

 

Hemoglobin A1c (HbA1c)

Hemoglobin A1c (HBA1c) estimates the average glucose level in the blood over the previous three months by counting the number of glucose molecules stuck on red blood cells. Glucose molecules on hemoglobin is called glycated, or glycosated hemoglobin.

When to check

Baseline. If abnormal, repeat every 3 months.

Standard reference ranges

Normal values: 4.0 to 5.5%

Pre-diabetes: 5.6 to 6.4%

Diabetes: ≥ 6.5% 

Critical value: >7.0%

 

Elevated values

Higher than normal values may be caused by:

  • Diabetes (type 1 and 2)
  • Pre-diabetes
  • Low red blood cell (RBC) turn over, e.g. anemia of iron deficiency
  • B12 deficiency, folate deficiency

 

Decreased values

Lower than normal values may be caused by:

  • High RBC turn over, e.g.hemolytic anemia
  • Use or abuse of erythropoietin (EPO)
  • Treatment for iron deficiency, B12 deficiency, or folate deficiency
  • Patients on hemodialysis (which alters the RBC turn over)

 

Low-carb considerations

Ordering HbA1c tests every three months can motivate and empower patients to continue the low carb diet. If values are dropping they get positive reinforcement; if values rise, they may be motivated to adhere more strictly to the low-carb diet. Rising values in formerly successful patients who may be slipping back into old dietary habits can convince them to get back on track.

Some patients have HbA1c levels that stall or even rise at the start of low-carb, especially as they reduce their diabetic medications. Let them know this is okay.

Example: a patient has a baseline HbA1c of 7.4%, but daily was taking 100 units of long acting insulin, a high dosage of a sulfonylurea, and an SGLT2-inhibitor. After going low-carb, the patient was able to discontinue all her diabetic medications within six months. Her six month HbA1c level is still 7.4%. The patient feels frustrated and confused that her HbA1c did not go down despite all her hard work.

This is a common situation in low-carb clinics. Tell patients this is a huge improvement! A lot of insulin plus three additional diabetic medications used to control their diabetes; now they don’t need any medications to have an HbA1c of the same level. Tell patients their body is functioning better and demonstrating increased insulin sensitivity.
 

More

HbA1c results may not be accurate for patients with chronic kidney disease (CKD), underestimating true blood glucose values. Results may also be inaccurate with some genetic hemoglobin variants, such as persistence of fetal hemoglobin (HbF) or existence of sickle cell anemia, either measuring too high or too low against real blood glucose values.

 

Complete lipid panel

The complete lipid panel measures total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglycerides. It is primarily used to assess cardiac risk and make decisions regarding treatment for patients who appear to be at high-risk.

When to check

Baseline. Repeat every 6 months. If a patient appears to be a hyper-responder — having LDL-C levels significantly higher on low carb — repeat every 3 months until stable, then repeat every 6 months.

Standard reference ranges
Total cholesterol
<200 mg/dL
<5.2 mmol/L
HDL-C
>40 mg/dL
>1.0 mmol/LL
LDL-C
<160 mg/dL
<4.0 mmol/L
Triglycerides
<160 mg/dL
<1.8 mmol/L
 

Low-carb considerations

Patients should fast for 12 hours prior to a lab test for a complete lipid panel as eating can cause large fluctuations in triglyceride levels. Most patients eating low carb will have much lower triglyceride levels. Low carb doctors consider the optimal triglyceride levels for patients on low-carb to be 70 mg/dL (<0.8 mmol/L).

Patients may experience unpredictable changes to their cholesterol values within the first three months of starting low-carb, such as elevations in all markers. The values appear to normalize once patients’ weight-loss stabilizes, between three to six months on low-carb. Checking cholesterol levels within the first three months can often cause unnecessary concern. It is recommended doctors wait to check cholesterol levels until patients’ weight-loss stabilizes.

Often low-carb doctors observe a dramatic improvement in their patients’ cholesterol markers after six months on low-carb. However, some patients have an elevation in total cholesterol, HDL-C and LDL-C, but a dramatic reduction in triglyceride levels. Doctors should correlate these results with a high-sensitivity c-reactive protein (hs-CRP) test to measure cardiac risk. Most doctors find that hs-CRP levels are extremely low, warranting no concern. These patients are called hyper-responders. To learn more about hyper-responders, and to better understand the current, rapidly changing role of cholesterol as a marker of cardiac risk. Please read our elevated cholesterol guide.


Creatinine

The creatinine test is a clinical marker for kidney function. Serum levels of creatinine, a waste product from the normal wear and tear of muscles, will vary depending on patients’ muscle mass, age, sex, and their glomerular filtration rate (GFR).

When to check

Baseline. Repeat every 6 months if abnormal or the patient is known to have CKD.

Standard reference ranges
0.8-1.4 mg/dL
61-107 µmol/L
 

Increased values

Higher than normal values may be caused by:

  • Acute tubular necrosis
  • Drug side effects, e.g. aminoglycoside antibiotics
  • Congestive heart failure
  • Dehydration
  • Diabetic nephropathy
  • Glomerulonephritis
  • Renal failure
  • Hypothyroidism
  • Muscular dystrophy
  • Pyelonephritis
  • Rhabdomyolysis
  • Shock
  • Urinary track obstruction

 

Decreased values

Lower than normal values may be caused by:

  • Decreased muscle mass
  • Myasthenia gravis
  • Muscular dystrophy

 

Low-carb considerations

Low-carb patients lose excess water weight in the first three months of adopting their new diet. Low-carb doctors often observe an initial increase in creatinine levels as a result. These levels return to normal within six months of maintaining a low-carb diet.

An increase in creatinine levels can be temporarily observed in patients who go off the low-carb diet for several weeks and then return to a low-carb lifestyle. This is a result of increased water retention from the return to a high-carb diet that is then lost once more as patients resume eating low-carb. Levels will return to normal within a few months of low-carb eating.

 

Microalbumin/creatinine ratio, urine

Microalbumin/creatinine ratio (urine) is commonly used as a marker to detect early diabetic nephropathy. Also known as microalbumin, ACR, UACR, urine albumin, the test measures when kidneys leak small amounts of albumin into the urine. Microalbuminuria is diagnosed either from a 24-h urine collection or from elevated concentration in a spot urine sample. Both must be measured on at least two of three measurements over a two to three-month period.

When to check

Baseline. If abnormal or the patient has CKD, repeat every 6 months. Once levels are stable, repeat annually.

Standard reference ranges
30-300 mg/L
30 to 300 mg/L

 

Increased values

Higher than normal values may be caused by:

  • Chronic kidney disease (CKD)
  • Cardiovascular disease
  • Type 1 or type 2 diabetes
  • Diabetic nephropathy
  • Hypertension
  • Vascular endothelial dysfunction

 

Low-carb reference considerations

Patients with CKD often hope that their renal function will improve once they lose weight and/or reverse their diabetes, but low-carb doctors rarely notice more than a slight improvement in renal function. Improved microalbumin/creatinine ratios for patients whose baseline level was below 30 mg/L may be observed over the course of five years. Patients whose baseline levels were greater than 30 mg/L do not demonstrate much improvement in their overall renal function.
 


Optional blood tests

Depending on other medical complications your patients may have — such as chronic kidney disease or hypothyroidism — you may want to order other tests. Patients may also struggle with the induction or keto flu when transitioning to a low-carb diet. Certain tests, such as sodium and vitamin B12, may help rule out any other factors that may be causing their symptoms.


Complete blood count (CBC)

CBC (complete blood count) measures the red, white and platelet blood cells in the blood. Red blood cells (erythrocytes) deliver oxygen for burning. White blood cells (leucocytes) are part of the immune system. Platelets (thrombocytes) help in the clotting process. Red blood cells live approximately 120 days, or 3 months, which is why the HbA1c is measured at least 3 months apart.

When to check

If your patient is struggling with fatigue.

Standard reference ranges
WBCs (white blood cells)
4,500-10,000 cells/mcL
RBC (red blood ceel count)
Women: 4 million-5 million cells/mcL
Men: 5 million-6 million cells/mcL
Women: X
Men:X
Hb or Hbg (hemoglobin)
Women: 12 to 15 gm/dL
Men: 14-17 gm/dL
Women: X
Men:X
Hct (hematocrit)
Women: between 36% and 44%
Men: between 41% and 50%
Women: X
Men:X
MCV (mean corpuscular volume)
MCV score is 80 to 95
Platelets
140,000-450,000 cells/mcL
 

Increased values

Higher than normal values may be caused by:

  • Congenital heart disease
  • Dehydration
  • High altitude
  • Hypoxia (such as from undiagnosed sleep apnea)
  • Malignancy
  • Polycythemia vera
  • Pulmonary fibrosis
  • Thalassemia

 

Decreased values

Lower than normal values may be caused by:

  • Anemia
  • Chronic renal failure
  • Alcohol dependence
  • Drug side effect, e.g. allopurinol
  • Liver disease

 

Low-carb considerations

Checking CBC may be helpful if your patient is experiencing unexplained fatigue or mental fog. These symptoms can also occur if the patient has a sub-optimal intake of fat or salt (leading to hyponatremia) or has the induction or keto-flu.

 

Electrolytes (sodium and potassium)

Sodium

Testing for sodium levels can help troubleshoot concerning symptoms, such as fatigue, muscle cramps and headache on a low carb diet. Sodium is an essential electrolyte that helps with blood volume regulation, blood pressure, fluid balance, nerve induction, muscle contraction, maintenance of osmotic equilibrium, and acid-base balance.

When to check

Baseline. Repeat every 6 months for patients with CKD

Standard reference ranges
134-144 mEq/L
134-144 mmol/L

 

Increased values

Higher than normal values may be caused by:

  • Cushing’s syndrome/disease
  • Dehydration
  • Too high dietary sodium intake
  • Type 1 or type 2 diabetes
  • Diabetes insipidus
  • Excessive diaphoresis
  • Ddvanced age
  • Hyperaldosteronism
  • Oral contraceptive pills
  • Vomiting

 
 

Decreased values

Lower than normal values may be caused by:

  • Drug side effects: e.g. ACE inhibitors, thiazide diuretics
  • Acute tubular necrosis
  • Adrenal insufficiency
  • Congestive heart failure
  • Cirrhosis
  • Diarrhea
  • Excessive exercise
  • Heavy sweating
  • Hypothyroidism
  • Malnutrition
  • Nephrotic syndrome
  • Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
  • Vomiting
  • Water intoxication
  • Too low dietary sodium intake

 

Low-carb considerations

Sometimes healthy patients and even renal patients, despite their CKD, must supplement with some good quality salt when adopting a low-carb diet. Patients who are no longer consuming excess sodium in processed food items will lose water weight, and may be less prone to water retention. Low-carb nephrologists often find that their CKD patients’ sodium levels may stay within the lower end of the normal reference range, but decrease enough to correlate with the patient experiencing minor symptoms of hyponatremia, such as headache, confusion, muscle cramps, weakness, and fatigue.

 

Potassium

Testing potassium (K+) levels can help trouble shoot muscle cramps, fatigue and other symptoms. Potassium is an essential electrolyte that is involved in a wide array of body functions, particularly muscle contraction, nerve conduction, heart rhythm, and acid-base balance.

When to check

Baseline. Repeat every 6 months for patients with CKD

Standard reference ranges

US units: 3.6-5.0 mEq/L
SI units: 3.6-5.0 mmol/L

 

Increased values

Higher than normal values may be caused by:

  • Drug side effects: e.g ACE inhibitors, angiotensen receptor blockers (ARBs), beta blockers, spironolactone and NSAIDs
  • Acidosis
  • Acute/chronic renal failure
  • Addison’s disease
  • Dehydration
  • Type 1 and 2 diabetes
  • Infection
  • Massive tissue damage
  • Massive hemolysis
  • Renal tubular acidosis

 

Decreased values

Lower than normal values may be caused by:

  • Ascites
  • Burns
  • Chronic pyelonephritis
  • Cushing’s syndrome
  • Drug side effects, e.g. diuretics, salicylates, prolong corticosteriods, exogenous insulin
  • Diarrhea
  • Eating disorders, especially bulimia and/or laxative abuse
  • Hyperaldosteronism
  • Hypothyroidism
  • Low potassium intake
  • Metabolic alkalosis
  • Renal tubular acidosis
  • Vomiting

 

Low-carb considerations

Potassium supplementation is generally not needed for most low-carb patients. However, it may be required for hypokalemia caused by other factors, such as Addision’s disease, corticosteroid treatment, use of diuretics, alcohol abuse, and Crohn’s disease. If, instead, your patient has hyperkalemia, see if adjustments to medications, such as for blood pressure, can be made. If they cannot, you will need to advise patients to avoid high potassium foods on low carb, such as avocados, mushrooms, spinach, and salmon.


Fasting insulin or c-peptides

Testing fasting insulin, or c-peptide, can provide insight into a patient’s degree of insulin production, insulin sensitivity or insulin resistance. Both tests give similar information so doing both is not necessary —choose the one most available in your region.

Both tests assess the body’s creation and use of insulin, a hormone secreted by the isles of Langerhans in the pancreas. Central to regulating carbohydrates and fat metabolism in the body, insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood. Insulin resistance is the underlying cause of type 2 diabetes.

A fasting insulin test is not as informative as a full Kraft Test (multiple insulin measurements tracking the response to glucose intake). However, it provides a much better snapshot of metabolic syndrome than simply fasting blood glucose or HbA1c and perhaps should considered a standard, not optional treatment.

Dr. Jason Fung: Why high insulin precedes type 2 diabetes

A c-peptide test is often measured as a means of distinguishing between type 1 and type 2 diabetes. C-peptide is a remnant from the multi-step creation of insulin by the pancreas. Its levels can indicate the amount of insulin the pancreas is making, or whether it is still producing any insulin at all. C-peptide levels in type 2 diabetes are normal or elevated. C-peptide in type 1 diabetes is low or non-existent.

When to check

Baseline and every 6 months

Standard reference ranges
Fasting insulin levels: 6-35 mU/mL
Fasting c-Peptides levels: 0.78-1.89 mg/mL
Fasting insulin levels: 42-243 pmol/L
Fasting c-Peptides levels:0.26-0.62 nmol/L

 

Increased fasting insulin

Higher than normal values may be caused by:

  • Acromegaly
  • Cushing’s syndrome
  • Type 2 diabetes
  • Drug side effects, e.g. glucocorticoids, hypoglycemic agents, insulin (exogenous)
  • Liver disease
  • Insulinoma
  • Obesity
  • Uremia

 

Decreased fasting insulin

Lower than normal values may be caused by:

  • chronic pancreatitis
  • Type 1 diabetes
  • Hypopituitarism.

 

Increased c-peptide values

Higher than normal values may be caused by:

  • Type 2 diabetes
  • Insulinoma
  • Renal failure

 

Decreased c-peptide values

Lower than normal values may be caused by:

  • Type 1 diabetes
  • Radical pancreatectomy
  • Latent adult onset diabetes (LADA)

 

Low-carb reference considerations

Educating patients about hyperinsulinemia and insulin resistance and checking either fasting insulin or c-peptide levels can motivate your patients. They will understand they are obese or diabetic because their insulin levels are too high. Results can reward them for sticking to the diet or encourage them to try harder.

However, insulin and c-peptide levels are very sensitive to stress, infection, lack of sleep or a recent high carb meal. Significant short term variations can be very frustrating for patients. Checking these levels every six months will capture longer-term trends.

Like fasting glucose, insulin over time is in less demand in a fat-burner than in a carb-burner. Once a low carb patient is fat-adapted, test results for both fasting insulin or c-peptide will be much lower.

Low-carb reference ranges for fasting insulin

US units: 0.3 – 5.8 mU/mL
SI units: 2 – 40 pmol/L

Many low carb experts try to target levels between 0.3 – 2.9 mU/mL

Low-carb reference ranges for fasting c-peptides

US units: 0.39 – 1.98 mg/mL
SI units:0.13 – 0.62 nmol/L

These are normal ranges for low carb patients, however, if they are consuming carbohydrates these levels could indicate the onset of juvenile type 1 diabetes or late onset type 1 diabetes (LADA). LADA should be considered in low carb patients whose insulin or c-peptide remains low but their blood glucose continues to rise [hyperlink to LADA section]

 

High-sensitivity c-reactive protein (hs-CRP)

The high-sensitivity c-reactive protein test (hs-CRP) is used as a marker for inflammation. Measuring and charting CRP values can help determine disease progress or the effectiveness of treatments. It can be a warning sign that the body is reacting to something in the diet (e.g. gluten or vegetable oils) or body (e.g. infection, chronic inflammation, damaged arteries).

CRP is synthesized by the liver as part of the body’s immune complement system, binding to dead or dying cells to help mark them for clearance by phagocytes.

When to check

Baseline. Repeat every 6 months for patients who have an inflammatory condition or appear to be hyper-responders.

Standard reference ranges

<3 mg/L

 

Increased values

Higher than normal values may be caused by:

  • Atherosclerosis
  • Rheumatoid arthritis
  • Autoimmune disease
  • Infections
  • Inflammatory disease
  • Malignancy

 

Low-carb considerations

CRP levels often reduce in patients on low carb diets, providing tangible evidence that inflammation is decreasing and reinforcing commitment to the lifestyle. If patients begin to consume more carbohydrates, CRP levels will often rise again and patients may describe increased symptoms of inflammation (e.g. joint pain.) Both the physical symptoms of increased inflammation and the elevation in CRP levels from the test can motivate patients to get back on track.

As discussed under the lipid panel test, when a low-carb patient appears to be a hyper-responder, having a concerning increase in LDL-C levels, CRP levels often decrease. This result can provide some reassurance to patients and healthcare practitioners that despite the elevation in LDL-C levels, markers for cardiac inflammation and CVD risk have reduced.


Nuclear magnetic resonance (NMR) lipoprofile

A nuclear magnetic resonance (NMR) lipoprofile, or particle test, is a more detailed test of total cholesterol that can help evaluate a patient’s risk of developing cardiovascular disease. This test can be particularly helpful in measuring low-density lipoproteins (LDL) particles, evaluating them according to their number, particle size and density. It is commonly ordered for patients believed to be at high-risk of cardiovascular disease or who have had a heart attack, but have normal LDL-C levels on the standard lipid panel.

When to check

Baseline and annually.
 

Low-carb considerations

This test is not available everywhere and usually is not required for most patients on a low carb diet. It may be helpful, however, for hyper-responder patients who see their LDL-C rises significantly on a low carb diet. The test can determine LDL particle size and density, distinguishing between the more concerning small dense LDL particles and larger, less-worrisome “fluffier” LDL particles. The Vertical Auto Profile (VAP) test can also determine LDL particle size and density where the NMR test is not available.

 

Thyroid stimulating hormone (TSH)

A thyroid-stimulating hormone test checks whether a patient’s thyroid may be underactive or overactive. The test measures blood levels of TSH, secreted by the pituitary to tell the thyroid how much T3 and T4 to produce. An abnormal TSH value does not always indicate hypo or hyperthyroidism. The interpretation of TSH also depends on blood levels of T3 and T4, as well as the clinical symptoms of thyroid conditions and a physical exam.

When to check

Baseline if the patient has a history of hypothyroidism and Hashimoto’s disease, and takes thyroid medication. Repeat every 3 months until levels stabilize, then repeat annually.

Standard reference ranges
0.35-5.5 µU/mL
0.35-5.5 mU/L

 

Increased values

Higher than normal values may be caused by:

  • Hypothyroidism
  • Hashimoto’s disease
  • The recovery phase of acute illness

 

Decreased values

Lower than normal values may be caused by:

  • Acute medical or surgical illness
  • Grave’s disease
  • Hyperthyroidism
  • Drug treatments, e.g. glucocorticoids or somatostatin analogs

 

Low-carb considerations

Patients with pre-existing hypothyroidism or Hashimoto’s disease may experience mild or even significant improvement of their thyroid function on a low carb diet. Some low-carb doctors have even been able to discontinue the thyroid medication of their hypothyroid patient. Other patients may need their thyroid medication reduced if they experience symptoms of hyperthyroidism, which may come in waves over a few months on a low carb diet. The low-carb diet does not need to be stopped during periods where the patient experiences symptoms of hyperthyroidism, but any fasting should be stopped until the patient is stable on the adjusted dosage of medication.

A frequent symptom of hypothyroidism is fatigue. This can be confused with a sub-optimal intake of fat, hyponatremia and the induction or keto-flu. Checking TSH levels can help determine why your patient may be experiencing these symptoms.


Uric acid

The uric acid test helps assess the patient on the metabolic syndrome spectrum. A product of purine breakdown, found in urine, uric acid levels are an independent risk factor for diabetes. Excess uric acid can cause gout and kidney stones. Levels can be affected by diet, alcohol consumption, and kidney function.

When to check

Baseline. Repeat every 6 months in patients with a history of gout.

Standard reference ranges
4.0 to 8.0 mg/dL
240 – 480 umol/L

 

Low-carb considerations

Uric acid can temporarily increase when patients start low-carb, especially if they also fast. This is only observed within the first six weeks as patients transition into a fat-burning state. Uric acid levels normalize within three months on low-carb.

Patients with a history of gout are more at risk of triggering another one in the first six weeks of going low carb. The pros and cons of prophylaxis treatment, such as using a short term prescription for allopurinol should be discussed with patients at risk for gout.

 

Vitamin B12

The vitamin B12 (cobalamin) test helps distinguish reasons for fatigue or other symptoms that may be related to diet, malabsorption, or malnutrition. Vitamin B12 is a water-soluble vitamin that plays a key role in the functioning of the brain and nervous system and the formation of red blood cells. It is involved in the metabolism of every cell of the human body, especially DNA synthesis and regulation, fatty acid synthesis, and energy production.

When to check

Baseline for vegetarian and vegan patients, and patients with a history of gastric bypass or lap-band surgery. If abnormal, repeat every 6 months.

Standard reference ranges
130-700 ng/L
150-500 pmol/L

 

Decreased values

Lower than normal values may be caused by:

  • Macrocytic anemia
  • Bowel resection (gastric bypass surgery, gastrectomy)
  • Celiac disease
  • Crohn’s disease
  • Dietary deficiency (veganism)
  • Helminth infection
  • Hyperthyroidism
  • Malabsorption
  • Drug side effects, e.g, metformin, oral contraceptive pill
  • Pernicious anemia
  • Pregnancy

 

Low-carb reference considerations

Excellent B12 levels should be expected on a low carb diet rich in animal products. If the patient has macrocytic anemia related to a B12 deficiency, this can lead to an inaccurate(higher) HbA1c test result. One of the most frequent symptoms of vitamin B12 deficiency is fatigue and mental fog, which can be confused with a sub-optimal intake of fat, hyponatremia or the induction or keto-flu. Checking vitamin B12 levels can help determine why your patient may be experiencing these symptoms.