What Blood Tests Should Be Monitored on a Ketogenic Diet?
A ketogenic diet can influence glucose regulation, insulin, blood lipids, fluid balance, liver and kidney markers, thyroid hormones and nutritional status.
Testing before starting provides a useful baseline. Follow-up testing shows the direction of change and helps determine whether the diet is effective, well tolerated and appropriately formulated.
People using ketogenic metabolic therapy for a mental health condition generally require closer monitoring, particularly when taking prescription medication.
1. Full Blood Count
A full blood count, or complete blood count, measures:
Red blood cells
Haemoglobin
Haematocrit
Red-blood-cell size
White blood cells
Platelets
What can it detect?
A full blood count can help identify patterns associated with:
Anaemia
Iron, vitamin B12 or folate deficiency
Infection or inflammation
Changes in platelets or other blood cells
It provides useful context for interpreting ferritin, HbA1c, vitamin B12 and folate. For example, anaemia or altered red-blood-cell turnover may affect the reliability of HbA1c.
2. Full Lipid Profile, ApoB and Lp(a)
Recommended markers:
Total cholesterol
LDL cholesterol
HDL cholesterol
Triglycerides
Non-HDL cholesterol
Apolipoprotein B, or ApoB
Lipoprotein(a), or Lp(a)
What can they detect?
A full lipid profile contributes to cardiovascular risk assessment and shows how lipid transport changes during the diet.
Triglycerides often decrease and HDL may rise during carbohydrate restriction. LDL responses vary considerably between individuals.
ApoB estimates the number of potentially atherogenic lipoprotein particles. It is particularly useful when LDL cholesterol and the wider metabolic picture appear discordant.
Interpret these results alongside blood pressure, glucose regulation, smoking, family history, body composition and overall cardiovascular risk. Low triglycerides and higher HDL do not automatically remove the significance of elevated ApoB or Lp(a).
3. HbA1c, Fasting Glucose and Fasting Insulin
What can they detect?
HbA1c estimates average blood glucose over approximately two to three months. It helps identify longer-term patterns associated with prediabetes, diabetes and improving or worsening glucose regulation.
Fasting glucose provides a snapshot of blood glucose after an overnight fast. It is influenced by hepatic glucose production, sleep, stress, illness, recent activity and test timing.
Fasting insulin may reveal elevated insulin demand before fasting glucose or HbA1c becomes clearly abnormal. Together, fasting insulin and glucose can be used to estimate HOMA-IR.
HbA1c and fasting glucose measure different aspects of glucose metabolism and may not always agree. Anaemia, iron deficiency, haemoglobin variants and altered red-blood-cell turnover can affect HbA1c. Fasting insulin also lacks a single universally accepted optimal range.
HbA1c and plasma glucose are established tests for diagnosing diabetes. ADA Standards of Care 2026
4. Liver Markers
Recommended markers:
Alanine aminotransferase, or ALT
Aspartate aminotransferase, or AST
Gamma-glutamyl transferase, or GGT
Alkaline phosphatase, or ALP
Bilirubin
Albumin
What can they detect?
These markers can help identify patterns associated with:
Fatty liver disease
Liver-cell injury
Impaired bile flow
Alcohol, medication or supplement effects
Reduced liver synthetic function
ALT and AST may rise temporarily after strenuous exercise, illness or medication use. GGT, ALP and bilirubin provide additional context when liver, gallbladder or bile-duct concerns are present.
One abnormal result rarely identifies the cause by itself. The pattern, symptoms and direction of change are more informative.
5. Kidney Markers
Recommended markers:
Creatinine
Estimated glomerular filtration rate, or eGFR
Urea
Urine albumin-to-creatinine ratio, or uACR
Cystatin C when appropriate
What can they detect?
Creatinine and eGFR help estimate kidney filtration. Urea may reflect kidney function, hydration and protein metabolism.
The uACR can detect albumin leaking into the urine. This may be an early sign of kidney damage even when eGFR remains within the expected range. Kidney assessment is more complete when eGFR and uACR are considered together. National Kidney Foundation
Creatinine is influenced by muscle mass, meat intake, creatine supplementation, hydration and recent exercise. Cystatin C may provide additional information when creatinine-based eGFR appears inconsistent with the wider clinical picture.
6. Electrolytes and Mineral Balance
Recommended markers:
Sodium
Potassium
Chloride
Bicarbonate
Magnesium
Calcium
What can they detect?
These markers help assess hydration, electrolyte regulation and acid–base balance.
During early keto adaptation, lower insulin levels can increase the loss of sodium and water through the kidneys.
Dizziness, weakness, headaches, muscle cramps or palpitations justify reviewing hydration, blood pressure, electrolyte intake, medication and general health.
Serum magnesium represents only a small proportion of total body magnesium. A result within the laboratory range does not always provide a complete assessment of magnesium status.
7. Thyroid Markers
Recommended markers:
Thyroid-stimulating hormone, or TSH
Free thyroxine, or free T4
Free T3 when clinically appropriate
Thyroid antibodies when autoimmune thyroid disease is suspected or established
What can they detect?
TSH and free T4 are the main tests used to assess thyroid function. They can identify patterns consistent with an underactive or overactive thyroid and help monitor thyroid treatment.
Free T3 may provide additional information in selected situations, although it is not routinely required for diagnosing hypothyroidism.
Thyroid results should be interpreted alongside symptoms, calorie intake, weight change, illness and medication. American Thyroid Association
8. Iron, Vitamin B12, Folate and Vitamin D
These tests are particularly relevant when there is fatigue, weakness, poor concentration, restricted food intake, digestive difficulty, heavy menstrual bleeding or a history of deficiency.
Iron assessment:
Full blood count
Ferritin
Serum iron
Transferrin or total iron-binding capacity
Transferrin saturation
These markers can identify patterns associated with iron deficiency, anaemia or iron overload. Ferritin also rises during inflammation, so it should be interpreted with the full blood count, transferrin saturation and clinical context.
Vitamin B12 and folate
These nutrients support red-blood-cell production, neurological function and DNA synthesis. Deficiency may contribute to anaemia, fatigue, cognitive changes, numbness or tingling.
Methylmalonic acid may provide additional information when vitamin B12 is borderline or the clinical picture remains unclear.
Vitamin D
Serum 25-hydroxyvitamin D may be appropriate when there is limited sunlight exposure, osteoporosis risk, malabsorption or a previous deficiency.
9. Inflammation
Possible markers:
C-reactive protein, or CRP
High-sensitivity CRP, or hs-CRP
What can they detect?
CRP is a nonspecific marker of inflammation. It may rise with infection, injury, inflammatory disease or recent strenuous exercise.
Hs-CRP can contribute to cardiovascular risk assessment when measured under stable conditions. A raised result should be interpreted carefully and may need repeating after temporary illness or inflammation has resolved.
10. Uric Acid
Uric acid may be particularly relevant for people with:
Gout
Kidney stones
Reduced kidney function
Previously elevated uric acid
Rapid weight loss
Ketones and uric acid can temporarily compete for excretion through the kidneys during early adaptation. This may cause a temporary increase in uric acid in some people.
A raised result should be interpreted alongside symptoms, kidney function, hydration, medication, alcohol intake and weight change.
11. Medication Blood Levels
This section is particularly important when keto is being used therapeutically for mental health or neurological conditions.
Some medications require measurement of their concentration in the blood. Lithium is a key example because changes in sodium intake, hydration, body weight and kidney handling can affect lithium levels.
Depending on the medication and clinical situation, monitoring may include:
Therapeutic drug levels
Kidney and liver function
Electrolytes
Blood glucose
Blood pressure
Medication side effects
Ketogenic therapy may alter medication response or requirements. Medication changes should be managed by the prescribing clinician.
Metabolic Mind recommends baseline and ongoing monitoring, including medication levels where required. Metabolic Mind guidance
Additional Monitoring for Ketogenic Metabolic Therapy
Blood tests provide only part of the picture. When ketosis is used to support a mental health condition, monitoring should also include:
Blood ketones
Blood glucose
Blood pressure
Weight and waist measurement
Sleep duration and quality
Mood and emotional stability
Anxiety
Energy
Cognition and concentration
Psychiatric symptoms
Signs of excessive activation, hypomania or mania
Medication effects and side effects
Blood ketones may be measured more frequently during the initial phase to identify individual patterns and the relationship between ketosis, symptoms and functioning.
Metabolic Mind emphasises establishing a baseline, tracking ketosis and working with a care team when ketogenic therapy is used for mental health. Metabolic Mind THINK+SMART guidance
Suggested Testing Frequency
A practical schedule may include:
Before starting: baseline testing
After 8–12 weeks: early metabolic and safety review
After 3–6 months: assessment of the established response
Every 6–12 months: ongoing monitoring when stable
Earlier or more frequently: when symptoms appear, medication changes, results fall outside the expected range or keto is being used therapeutically
People taking glucose-lowering, blood-pressure, thyroid, psychiatric or other relevant medication may require closer monitoring from the beginning.
Interpretation Limitations
Blood-test results are influenced by:
Fasting duration
Hydration
Recent meals
Exercise
Sleep
Stress
Infection or inflammation
Menstrual cycle
Medication and supplements
Weight loss
Laboratory methods
The most useful approach is to compare results obtained under similar conditions and observe the direction of change over time.
Laboratory findings should be interpreted alongside symptoms, blood pressure, body composition, diet quality, medical history, medication and the reason for using the ketogenic diet.
Final Perspective
Monitoring should answer four questions:
Is metabolic health improving?
Is the ketogenic diet well tolerated?
Are medication and mental-health changes being managed safely?
Does the plan need to be adjusted?
A clear baseline, appropriate follow-up and careful interpretation allow ketogenic nutrition and ketogenic metabolic therapy to remain personalised, responsible and sustainable.
If you would like support in building a calm, well-structured ketogenic approach, you can book a free 15-minute discovery call.
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