Creatinine, BUN & eGFR: What Kidney Labs Really Tell You

What Creatinine, BUN & eGFR Actually Measure

(Quick, clear, no-jargon explanations — promise.)

Creatinine: Your “waste product” indicator

Creatinine is produced when muscles break down — totally normal.
Your kidneys filter it out through urine.

So:

• High creatinine = kidneys may not be filtering efficiently

• Low creatinine = usually low muscle mass, aging, or malnutrition

• Mild bumps = dehydration or poor circulation (this is super common!)

It’s less about “kidney failure” and more about “how well the filters are flowing.”

BUN (Blood Urea Nitrogen): Your hydration + protein + stress marker

This one gets misread constantly.

BUN rises when:

• You’re dehydrated

• You’re stressed

• You’re eating more protein

• You’re taking steroids

• You don’t sleep well

• You’re sick or inflamed

A high BUN doesn’t always mean kidney disease — more often it means life has been… life-ing.

eGFR (Estimated Glomerular Filtration Rate): Your “efficiency score”

This number tells us how efficiently your kidneys are filtering, based on age, sex, race, and creatinine.

Ranges:

• 90+ = Great

• 60–89 = Mild decline (very normal with age)

• <60 = Possible kidney disease; requires monitoring

• <45 = Moderate decline

• <30 = Significant decline

But here’s the nuance nobody tells you:
eGFR naturally drops with age, even in totally healthy people.

So don’t panic if yours is in the 60s — context matters.

Why These Labs Matter (Even If You Feel Fine)

Your kidneys play a huge role in:

• Blood pressure

• Electrolyte balance

• Detoxification

• Hormone regulation

• Water balance

• Red blood cell production

• Blood sugar + insulin sensitivity

Women often show early stress signs long before symptoms appear:

• Fatigue

• Foot or ankle swelling

• Brain fog

• High blood pressure

• Trouble concentrating

• Low appetite

• Foamy urine (yes, we talk about it here)

Your kidney labs tell the story of how your body handles hydration, stress load, protein metabolism, and circulation.

Understanding Your Numbers

(General ranges — your lab may vary)

Creatinine

• Women: ~0.5–1.1 mg/dL
  Higher if muscular. Spikes with dehydration.

BUN

• Normal: 7–20 mg/dL
  But rises easily with dehydration or high-protein diets.

eGFR

• 90–120: Optimal

• 60–89: Mild reduction, often age-related

• <60: Needs follow-up and repeat labs

• <30: Specialist care

⚠️ Note: Medications, illness, and menstrual cycle changes can shift these numbers.

Factors That Influence Kidney Labs (Beyond “Kidney Health”)

This is where women breathe a sigh of relief because nobody ever explains this.

1. Hydration

Not enough water = elevated creatinine + BUN.

2. Stress hormones

Cortisol affects circulation → can temporarily lower eGFR.

3. Blood sugar instability

High glucose damages filtration long-term.

4. Medications

NSAIDs, PPIs, antibiotics, and ACE inhibitors can shift numbers.

5. Exercise

Heavy lifting increases creatinine due to muscle breakdown.

6. Menstrual cycle

Hormonal shifts influence fluid retention + lab values.

How to Support Healthy Kidney Function (Naturally, Safely)

No gimmicks. No detoxes. Just supportive habits.

• Stay hydrated consistently (not just chugging at night)

• Balance blood sugar (your kidneys LOVE stability)

• Move daily — improves circulation

• Prioritize sleep — repair processes happen overnight

• Don’t overuse NSAIDs — sneaky kidney stressor

• Eat enough protein, but not extreme levels

And most importantly:
Track trends, not one-time numbers.