Monitoring patients on low carb: Lab tests

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Below is the recommended list of blood tests and the frequency at which you may want to order them. Consider monitoring the tests listed in the “every 3 months” column at that frequency until the patient’s disease is reversed and stable.

Click on each test to see a comprehensive definition, a differential diagnosis for increased and decreased values, as well as the standard normal values.

Note that the normal ranges are sometimes slightly different for patients on low carb/keto, and our lab test guide goes into those differences as well.

Obesity, metabolic syndrome and type 2 diabetes

For patients with obesity, metabolic syndrome and type 2 diabetes, here are the core recommended lab tests to consider:

HbA1c
Fasting glucose
Complete lipid panel
Fasting insulin OR fasting c-peptide
Creatinine
ALT

Test	Baseline and annually	Every 3 months	Purpose
Hemoglobin A1c (HbA1c)	X	X (if elevated)	To measure the reduced risk of developing diabetes and/or monitor the improvement in a person’s diabetes, and to aid in treatment decisions. Also useful for motivational purposes, and to quickly identify carb creep.
Fasting glucose	X	X	To monitor for hyperglycemia and hypoglycemia, and to aid in treatment decisions.
Complete lipid panel (Total cholesterol, LDL, HDL, trigs)	X	X (initially)	To assess the risk of heart disease and to assess insulin resistance. Furthermore, patients often feel more at ease with regular cholesterol tests initially, especially until they’ve seen their triglycerides plummet and HDL go up (with explanations). Finally, though controversial and still of unproven benefit, it may be valuable to find the small percentage of patients who are “hyper-responders” and may end up with very high LDL, to potentially take precautions.
Fasting insulin	X	X	To help evaluate pancreatic function by measuring insulin production by beta cells, and to help identify patients with latent onset type 1 diabetes. *important to check at baseline if your patients will be fasting to ensure they are not latent onset type 1 diabetics.
C-peptide (Alternative to fasting insulin)	X		To help evaluate insulin production by the beta cells in the pancreas, and to help identify patients with latent onset type 1 diabetes. *important to check at baseline if your patients will be fasting to ensure they are not latent onset type 1 diabetics.
Alanine aminotransferase (ALT)	X	X	To screen for liver damage and/or diagnose liver disease, as well as measure improvements in liver function as NAFLD improves.
Creatinine	X	X	In addition to monitoring and diagnosing a patient’s renal function, this test helps us determine whether or not the patient is adequately hydrated.

Pre-existing conditions

Below you’ll find tests that are recommended with for patients with certain pre-existing conditions, on a very low-carb diet.

Electrolytes (if on diuretics, or with chronic kidney disease)
TSH (if on thyroid medication)
Uric acid (if history of gout)
Hs-CRP (for people with inflammatory disease, sometimes improves on low carb)
Albumin/creatinine ratio (for people with diabetes, may improve, can be helpful for motivational purposes and show that their kidneys are getting healthier)

Test	Baseline and annually	Every 3 months	Purpose
Sodium	X	X	To ensure the patient is adequately hydrated and at risk for hyponatreamia or hypernatreamia. Sodium supplementation may be necessary in some cases.
Potassium	X	X	To ensure the patient’s potassium levels are not affected by medications or other health conditions, and assess their risk for hypokalemia and hyperkalemia. Potassium supplementation may be necessary in some cases, or a low-potassium diet may be required in others.
Uric acid	X	X	These levels can become elevated during the initial transition period to low-carb diets. At baseline: can help you identify patients at risk for gout and/or kidney stones and take preventative measures to prevent those conditions.
Calcium	X	X	To screen for, diagnose, and monitor a range of conditions.
Phosphorus	X	X	To determine whether or not a patient should reduce the phosphorus in their diets, especially if they have renal disease.
Magnesium (RBC magnesium if available)	X	X	To evaluate the level of magnesium in your blood and determine whether or not some common side effects of low carb, such as cramping, can are the cause of magnesium deficiency rather than worsened neuropathy. RBC magnesium is a better measure because it measures tissue magnesium levels.
Thyroid-stimulating hormone (TSH)	X	X	To monitor any changes in thyroid function.
Free T3	X		To evaluate thyroid gland function.
T4	X		To evaluate thyroid gland function. To help evaluate thyroid gland function; to help diagnose thyroid disease; to screen for; hypothyroidism in newborns; to monitor effectiveness of treatment.
Vitamin B12 (MMA test if available)	X		To evaluate whether or not a person has any deficiency (frequent with bariatric surgery patients and vegetarians), and to help diagnose anemia or neuropathy.
High-sensitivity c-reactive protein (hs-CRP)	X		To assess the risk of developing cardiovascular disease as well as monitor other areas of inflammation in the body.
Albumin	X		To verify sufficient protein in the plasma. It can be decreased with celiac disease, chronic liver disease, cirrhosis, Crohn’s disease, diabetes mellitus, inflammatory bowel disease, malabsorption, malnutrition, protein losing enteropathy, etc. I’m not sure how useful this is with LCHF patients, and I am not sure it would change my conduct.
Albumin, creatinine ratio, urine	X	X	To detect and/or monitor kidney disease in patients who have or are at high risk for developing diabetes, or have hypertension.
CBC (complete blood count)	X	X	To measure white blood cells, red blood cells and platelets. Anemia is not rare with females, chronic extreme dieters, and bariatric surgery patients.
Vitamin D	X		Vitamin D deficiency is very common, in particular in Northern countries, and with people with metabolic syndrome. Deficiencies are linked to increased fatigue, chronic pain/inflammation, and osteoporosis. If normal at baseline, it can be checked annually. If abnormal and supplementation is given, it should be checked again every 3 months until normal.
Ferritin	X		To assess the iron reserve in the body. It can be low without anemia, and may require supplementation. If normal at baseline, it can be checked annually. If abnormal at baseline, it can be checked every 3 months until normal.

Optional, not related to low carb, but sometimes valuable for other reasons for patients that start a low-carb diet.

B12 (post bariatric surgery patients, consider at baseline for vegetarians/vegans)