CGMs, one-off BP readings and vitamin D: what's new at Peak Human this week

A note from Dr. Goel

Colleagues, here's what's new at Peak Human this week. I published three evidence reviews aimed at questions that land in primary care: do non-diabetic patients benefit from a continuous glucose monitor, how much can a single office blood pressure reading tell you, and where vitamin D stands after the large randomized trials.

— Dr. Sanjeev Goel

The Best CGMs of 2026, Compared

HbA1c: Meta-analysis of 8 RCTs (541 people with non-insulin type 2 diabetes): CGM lowered HbA1c by 0.37 percentage points (Aronson et al., 2025).

Without diabetes: The review finds no trial showing hard-outcome benefit in people without diabetes, and notes a February 2026 FDA Class I recall of certain FreeStyle Libre 3 / 3 Plus sensor lots.

How Accurate Is One Blood Pressure Reading?

Variability: VA analysis of 444 patients and 111,181 systolic readings: large within-person variability; averaging about five or six readings helped most (Powers et al., Ann Intern Med 2011).

Cuff size: CuffSZ trial (n=195): a regular cuff on an extra-large arm read 19.5 mm Hg too high (Ishigami et al., JAMA Intern Med 2023).

Vitamin D: Supplement or Sunlight?

VITAL: 25,871 US adults, 2,000 IU/day, about 5.3 years: cancer HR 0.96, all-cause death HR 0.99 (Manson et al., 2019).

Bottom line: The review still supports correcting true deficiency and cautions about very high doses.

My take: The blood pressure review is the one I'd pass to your whole clinic. In the VA data, no single clinic reading between 120 and 157 mm Hg could classify control status with 80% confidence. Validated upper-arm devices, the right cuff size, duplicate readings and a week of home monitoring will change more management decisions than most of the technology we discuss.

⚕️ Important disclaimer

This newsletter is for educational purposes only and is not medical advice. Compounds discussed may be investigational and not FDA-approved. Nothing here is a recommendation to start, stop, or change any treatment. Peptide and metabolic therapies carry real risks and should only be used under qualified medical supervision. Always consult your physician before making health decisions.