Blood Test Report Guide: What the Numbers Mean and How to Prepare

In my earlier post I explained which basic tests most adults need. This guide goes one step further: what the common numbers in a blood test report mean, which extra tests suit which people, and how to prepare so your report is accurate.

Step 1: Measure at home first

• Waist-to-height ratio: keep your waist less than half your height (NICE 2022). Example: height 170 cm → waist below 85 cm.
• Waist size for Indians: risk rises at 90 cm or more in men and 80 cm or more in women (Misra et al., 2009).
• Blood pressure and resting heart rate: track the trend, not one reading.

Step 2: Understand the main numbers

Blood sugar (ADA 2026)

Test	Normal	Prediabetes range	Diabetes range*
Fasting plasma glucose	Below 100 mg/dL	100–125	126 or more
HbA1c	Below 5.7%	5.7–6.4%	6.5% or more
2-hour OGTT (75 g)	Below 140 mg/dL	140–199	200 or more

*Use a lab whose HbA1c method is NGSP-certified and standardised to the DCCT reference — a point-of-care or non-certified machine is not reliable for diagnosis. A fasting glucose below 70 mg/dL is low (hypoglycaemia) and should be discussed with your doctor, especially if you take diabetes medicines. Diabetes is usually confirmed with a repeat test, unless there are clear symptoms. HbA1c can be misleading in anaemia, iron or B12 deficiency, haemoglobin disorders, kidney disease and pregnancy — your doctor may use glucose or OGTT instead. In PCOS, the 2023 international guideline prefers the OGTT.

Cholesterol — Indian guideline (CSI 2024)

Your risk level (decided by doctor)	LDL-C target	Non-HDL target
Low / moderate	Below 100 mg/dL	Below 130 mg/dL
High (e.g. diabetes with risk factors, or chronic kidney disease)	Below 70 mg/dL	Below 100 mg/dL
Very high (e.g. after heart attack or stroke)	Below 55 mg/dL	Below 85 mg/dL

• Fasting is usually not required for a lipid profile (CSI 2024). Your doctor may ask for a fasting test if triglycerides were very high.
• Lp(a) is mostly genetic. CSI recommends measuring it at least once in a lifetime; the desirable level is below 50 mg/dL. It is especially useful if there is early heart disease in the family.
• ApoB can help in selected people (for example, familial high cholesterol or high triglycerides). It is not a routine test for everyone.
• CSI advises that everyone should have a lipid profile by age 18.

hs-CRP (inflammation marker)

Below 1 mg/L = lower risk, 1–3 = average, above 3 = higher heart risk (AHA/CDC). A value above 10 usually means a current infection or inflammation — repeat after recovery. Test twice, about 2 weeks apart, and never use it alone.

Kidney (KDIGO 2024)

Test	Normal	Needs attention
eGFR	90 or more (60–89 may be normal with age if urine is normal)	Below 60 for 3 months or more
Urine albumin-creatinine ratio (uACR)	Below 30 mg/g	30–300 (moderately raised); above 300 (severely raised)

Avoid heavy exercise for 24 hours before the urine test, and don’t test during periods or a urine infection.

Liver

ALT and AST ranges depend on the lab (often up to about 35–40 U/L). A mildly raised value can be due to fatty liver, alcohol, medicines or recent heavy exercise. If it stays high, your doctor may advise an ultrasound or other tests.

Blood and iron

• Haemoglobin: anaemia is below 13 g/dL in men and below 12 g/dL in non-pregnant women (WHO 2024). In pregnancy the cut-off is lower — below 11.0 g/dL in the first and third trimesters, below 10.5 g/dL in the second.
• Ferritin: below 15 µg/L suggests iron deficiency in adults (WHO 2020). Ferritin rises with infection or inflammation, so a “normal” ferritin can hide deficiency — your doctor reads it with CRP and CBC.

Vitamins

• Vitamin B12: many labs treat below ~200 pg/mL as low and ~200–300 as borderline. Borderline results may need homocysteine or MMA testing. Common in vegetarians and people taking metformin long term.
• Vitamin D (25-OH): labs often call below 20 ng/mL deficient and 20–29 insufficient, but experts disagree on the ideal level. The Endocrine Society (2024) suggests not testing routinely in healthy adults.

Step 3: Extra tests for specific groups (not for everyone)

If you are…	Discuss with your doctor
Vegetarian / eat little animal food	Vitamin B12, iron studies; enough protein; strength training
A woman with PCOS	OGTT, lipid profile, ALT/AST, waist; liver ultrasound if advised
Using tobacco or alcohol	Yearly mouth examination; liver tests; lung function test if you have breathing symptoms
From a family with early heart attack, stroke or diabetes	Start screening earlier; Lp(a) once; ApoB and hs-CRP if advised
An endurance athlete	Iron and ferritin; ECG or echo only if symptoms or family history
Diabetic or have high BP	Urine albumin (uACR) and eGFR regularly; eye and foot checks

Step 4: How to prepare for your blood test

Situation	What to do
Fasting glucose, fasting insulin, homocysteine	Fast 8–12 hours. Water is fine. No tea, coffee or smoking.
Lipid profile	Usually no fasting needed. Avoid a very heavy, oily meal the night before.
Alcohol	Avoid for 24–48 hours before lipid, liver and uric acid tests.
Exercise	Avoid heavy workouts for 24 hours before lipid, liver, CK, uric acid and urine albumin tests.
Biotin (hair/skin/nail pills)	High doses can give false thyroid, hormone and heart (troponin) results (US FDA). Tell the lab; stop 48–72 hours before only if your doctor agrees.
Fever or illness	Delay routine screening tests (especially hs-CRP) until about 2 weeks after recovery. Never postpone a test your doctor has ordered to investigate the current illness.
Periods or urine infection	Delay urine tests until they are over.
Vitamin B12 or D supplements	Skip that morning’s dose; tell the lab about recent high-dose injections or tablets.
Prescription medicines	Never stop them without your doctor’s advice.

Key takeaways

1. Measure waist, weight and BP at home and track trends.
2. Know the main cut-offs, but compare with your lab’s range.
3. Lipid profile usually doesn’t need fasting; Lp(a) once in a lifetime is recommended in India.
4. Extra tests depend on your risk group — not every test is for everyone.
5. Prepare correctly so your report is accurate, and review it with a doctor.

Sources

1. American Diabetes Association. Diagnosis and Classification of Diabetes — Standards of Care in Diabetes 2026 — cut-offs for fasting glucose, HbA1c and OGTT
2. Cardiological Society of India. CSI Clinical Practice Guidelines for Dyslipidemia Management, Indian Heart Journal (2024) — LDL and non-HDL targets; non-fasting lipids acceptable; Lp(a) once in a lifetime; first lipid test by 18
3. Pearson TA et al. Markers of Inflammation and Cardiovascular Disease — AHA/CDC scientific statement, Circulation (2003) — hs-CRP risk categories; repeat test; ignore values above 10 during illness
4. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD — eGFR and urine albumin (uACR) categories
5. WHO. Guideline on haemoglobin cutoffs to define anaemia (2024) — anaemia: Hb below 13 g/dL in men and 12 g/dL in non-pregnant women
6. WHO. Guideline on use of ferritin concentrations to assess iron status (2020) — ferritin below 15 µg/L suggests iron deficiency in adults; higher cut-off during inflammation
7. Endocrine Society. Vitamin D for the Prevention of Disease — Clinical Practice Guideline (2024) — against routine vitamin D testing in healthy adults
8. Teede HJ et al. Recommendations from the 2023 International Evidence-based Guideline for PCOS, JCEM (2023) — 75 g OGTT is the preferred test for blood sugar status in PCOS
9. US FDA. Biotin interference with troponin and other lab tests — safety communication (updated 2019) — high-dose biotin can give falsely high or low results
10. NICE. Keep the size of your waist to less than half of your height (2022) — waist-to-height ratio
11. Misra A et al. Consensus statement for obesity and metabolic syndrome in Asian Indians, JAPI (2009) — waist ≥90 cm men, ≥80 cm women