When the check-up results arrive, most people read only the verdict on page one — “normal A / normal B / suspected condition” — and file it away. Yet the numbers inside flag trouble long before symptoms appear.
That matters most for the liver and kidneys, the “silent organs.” They don't hurt until damage is well advanced. So these two are checked with numbers, not symptoms.
1. What should I look at. The liver and kidneys are the “silent organs” — they do not hurt until damage is well advanced, so they are checked with numbers, not symptoms. Korea's standard health check already includes liver function (AST, ALT, γ-GTP) and kidney function (creatinine, eGFR, urine protein) — the answer is on the result you already have.
2. One threshold does not agree. The widely quoted “eGFR of 90 or above is fine” is not the line NIDDK draws — NIDDK puts the lower bound of normal at 60. This article sets both out and asserts neither.
3. Do not judge on one reading. AST is also present in muscle, so hard exercise before the test raises it temporarily — repeat tests and the trend matter more than a single value. And normal numbers do not rule out fatty liver.
Liver numbers — what do AST, ALT and γ-GTP show
AST and ALT are enzymes inside liver cells. When those cells are damaged, the enzymes leak into the blood and the values rise. In other words, a rise means liver cells are being injured.
- ALT is relatively liver-specific, so an isolated rise points first to fatty liver or hepatitis.
- γ-GTP responds sensitively to alcohol and bile-duct problems, and falls fairly quickly when you cut back.
- Fatty liver can exist with normal values — it's often found on ultrasound instead.
Note: AST is also present in muscle, so hard exercise before the test can raise it temporarily. The trend across repeat tests matters more than one reading.
Kidney numbers — what do creatinine, eGFR and urine protein show
- Serum creatinine — a waste product from muscle use that the kidneys filter out. When function drops, it accumulates in the blood and rises. (High muscle mass can raise it even with normal kidneys.)
- eGFR — an estimate of how much blood the kidneys filter per minute, adjusted for age and sex. Broadly, 90 or above is good, while below 60 persisting three months or more raises suspicion of chronic kidney disease.
- Urine protein — checks whether protein is leaking into urine; healthy results are usually negative. A positive can signal a filtering problem and warrants repeat and detailed testing. (Intense exercise or fever can cause a temporary positive.)
Is an eGFR of 90 reassuring
| GFR | NIDDK wording |
|---|---|
| 60 or more | “a GFR of 60 or more is in the normal range” |
| Below 60 | “a GFR of less than 60 may mean you have kidney disease” |
| 15 or less | “a GFR of 15 or less is called kidney failure” |
Neither is wrong so much as they mark different lines — “normal” versus “optimal”. This article uses the number NIDDK actually prints.
There is a second number, in the urine
“Albumin is a protein that can pass into the urine when the kidneys are damaged.”
“A urine albumin result of 30 mg/g or less is normal.”
— US NIDDK, chronic kidney disease tests and diagnosis
A standard check-up reports urine protein as positive or negative. What NIDDK describes is the urine albumin-to-creatinine ratio (uACR) — a number. Albumin can be leaking while urine protein reads negative. If you have diabetes or high blood pressure, it is worth asking for.
Who should be tested, and how often
| If you have (NIDDK) | Frequency |
|---|---|
| Diabetes | Every year |
| High blood pressure | “talk with your health care provider about how often you should get tested” |
| Heart disease | |
| A family history of kidney failure |
※ If albumin shows up, NIDDK advises repeating the urine test “one or two more times”. One positive is not a diagnosis.
If your blood sugar sits awkwardly high, see the prediabetes guide; for weight and waist thresholds, BMI and waist circumference.
If your body is showing signs, is it late
These symptoms tend to appear once things have already progressed — another reason to check the numbers first.
- Kidneys — foamy urine that doesn't settle, swelling around the eyes and ankles, frequent night urination, unexplained fatigue or itching
- Liver — heavy fatigue, poor appetite, discomfort under the right ribs, yellowing of the eyes or skin (jaundice), darker urine
What if your numbers are borderline high
| What | Which numbers | Backing |
|---|---|---|
| Cut alcohol | γ-GTP and liver values | Commonly advised |
| Lose 5–10% over six months | Fatty liver | NHIS webzine |
| Manage blood pressure and glucose | Kidneys | NIDDK — diabetes and hypertension head its testing list |
| 200–300 minutes aerobic, strength twice a week | Weight and glucose | NHIS webzine |
| Care with painkillers and supplements | Liver and kidneys | Commonly advised — tell your doctor what you take |
If you are unsure where to start with exercise, see home workout basics or chair exercises. Age-related muscle loss is covered in the sarcopenia guide.
- Cut alcohol — the most direct lever on γ-GTP and liver values.
- Lose 5–10% of body weight — the most effective step for fatty liver.
- Manage blood pressure and glucose — hypertension and diabetes are the two leading causes of chronic kidney disease. (See also the prediabetes signs guide.)
- Be careful with painkillers and supplements — they can burden the liver and kidneys. Tell your doctor what you take.
- Repeat the test — don't judge on a single value; recheck when your doctor advises.
Questions this raises
Is “normal B” fine?
It means no suspected disease, but you're in a borderline zone needing lifestyle change. Ignored, it often becomes “suspected condition” at the next check.
My liver values are slightly high but I feel nothing.
The liver typically causes no symptoms until damage is significant. Treat feeling fine as expected, and focus on finding the cause (fatty liver, alcohol, medication, hepatitis).
Does a low eGFR mean dialysis?
No. Early on, the goal is slowing progression through blood-pressure and glucose control and lifestyle. Earlier detection means more room to manage.
How should I prepare for the test?
Generally fast for 8+ hours and avoid heavy drinking or intense exercise the day before, which can distort values.
By the time the liver and kidneys hurt, it's late. The numbers in that filed-away report speak long before symptoms do.
Sources
- US National Institute of Diabetes and Digestive and Kidney Diseases — Chronic Kidney Disease Tests & Diagnosis. Source of GFR 60 or more normal, below 60 may mean kidney disease, 15 or less is kidney failure, urine albumin of 30 mg/g or less is normal, “albumin is a protein that can pass into the urine when the kidneys are damaged”, who should be tested (diabetes, high blood pressure, heart disease, family history of kidney failure), yearly testing with diabetes, and repeating the urine test.
- US Centers for Disease Control and Prevention — Diabetes Testing (last reviewed 15 May 2024). Source of the fasting glucose and A1C bands that appear on the same report.
- National Health Insurance Service (Korea) — health insurance webzine (July 2024). Source of the weight-management targets that drive fatty liver improvement — 5–10% over six months, 200–300 minutes of aerobic exercise a week, strength work twice a week.
Where to check further
- Reference ranges for AST, ALT and γ-GTP. Labs use different ranges, so no numbers appear here — the reference range printed on your own result is the one that applies.
- The “three months” in “an eGFR below 60 for three months or more is chronic kidney disease”. Widely used, but the NIDDK page we opened states no duration — the Korean Society of Nephrology guidelines and your clinician can confirm it.
- When the NIDDK kidney page was last updated. It is marked October 2016 and may lag current guidance — the KDCA health information portal carries the Korean position on chronic kidney disease.
Written as of July 2026. The kidney thresholds come from NIDDK originals. This is general health information and does not replace medical diagnosis or treatment. Reference ranges vary by laboratory and individual — always review results with a healthcare professional.
To see what you can have before the result sheet arrives, the eligibility calculator names it screening by screening — including that lung is the one with an upper age limit.
