When should serum testosterone be rechecked after initiating testosterone 100 mg every two weeks?

When to Recheck Testosterone After Starting 100 mg Every 2 Weeks

Recheck serum testosterone 3 to 6 months after initiating testosterone 100 mg every 2 weeks, drawing blood midway between injections (at approximately 1 week after the last injection). 1

Timing of Blood Draw is Critical

The Endocrine Society guidelines are explicit about when during the injection cycle to draw blood for injectable testosterone enanthate or cypionate:

• Draw blood midway between injections - for a 2-week dosing interval, this means approximately 7 days after the last injection 1
• This timing captures a representative level rather than the peak (which occurs shortly after injection) or trough (just before the next dose)
• The goal is to achieve mid-normal range testosterone levels (approximately 400-700 ng/dL) at this midpoint measurement 1

Initial Monitoring Timeline

After starting therapy:

1. First testosterone level check: 3-6 months after initiation 1, 2, 1
2. Clinical evaluation: 3-6 months after starting treatment to assess symptom response and adverse effects 1
3. Hematocrit monitoring: baseline, then 3-6 months, then annually 1

The 2010 and 2018 Endocrine Society guidelines consistently recommend this 3-6 month window for initial testosterone monitoring across all guideline iterations, making this the standard of care.

Dose Adjustment Criteria

When you get that mid-cycle testosterone level at 3-6 months:

• If testosterone >700 ng/dL (24.5 nmol/L): reduce dose or increase injection frequency 1
• If testosterone <400 ng/dL (14.1 nmol/L): increase dose or decrease injection interval 1
• The 2018 guideline uses slightly different thresholds: >600 ng/dL or <350 ng/dL 3

Common Pitfall: Every-2-Week Dosing May Not Be Optimal

Important caveat: 100 mg every 2 weeks is a relatively low dose with a long interval. Many patients experience:

• Peak-related symptoms early in the cycle (acne, mood changes, fluid retention)
• Trough-related symptoms late in the cycle (fatigue, low libido, erectile symptoms) 4

If symptoms fluctuate throughout the 2-week cycle despite achieving mid-normal testosterone levels at the midpoint, consider more frequent dosing (weekly or twice-weekly) rather than simply increasing the total dose 4. This creates more stable testosterone levels and may improve symptom control without increasing total weekly testosterone exposure.

Safety Monitoring Beyond Testosterone Level

At that same 3-6 month visit, also check:

• Hematocrit: stop therapy if >54% 1, 3
• PSA and digital rectal exam (if age ≥40 years with baseline PSA >0.6 ng/mL): check at 3-6 months 1
• Symptom response: assess libido, energy, erectile function, mood 1

The hematocrit monitoring is particularly important because testosterone-induced erythrocytosis is dose-dependent and more common in older men 1. A hematocrit >54% requires therapy interruption until it normalizes, then reinitiation at a lower dose.

After Initial Monitoring

Once stable on therapy with appropriate testosterone levels and no adverse effects:

• Testosterone levels: can be checked annually or when symptoms change 1
• Hematocrit: annually 1
• Clinical evaluation: annually 1
• PSA/DRE: according to age-appropriate prostate cancer screening guidelines 1