Five Patterns Worth Checking
Iron stores. Ferritin reflects stored iron and can decline before obvious anemia develops but it also rises with inflammation, which is why Rythm pairs it with hsCRP. (Women with suspected anemia still need a conventional CBC and full iron studies through a provider.)
Thyroid signaling. TSH, Free T4 and free T3, read together and in context a low free T3 during hard dieting or heavy training is often adaptation, not disease.
Hormone availability. Total testosterone alone misleads; free testosterone (from total T, SHBG, and albumin) plus estradiol shows what's actually available. For women, cycle stage matters; on TRT or HRT, dose timing matters even more.
Recent energy and glucose. Fructosamine reflects average glucose exposure over roughly the preceding two to three weeks useful during dieting, weight loss, or big dietary changes, alongside triglycerides and HDL.
Inflammation and recovery. A repeatedly elevated hsCRP while you're otherwise well means something different from one spike during a cold.
The Context Markers
Creatinine and eGFR add kidney-filtration context; GGT, ALP, and albumin cover selected liver, protein, and fluid physiology; and for men, hemoglobin and calculated hematocrit provide red-cell and oxygen-carrying context especially relevant on TRT, since testosterone can stimulate red blood cell production. None of these diagnose fatigue. They keep the headline markers from being read in isolation.
What a Normal Panel Doesn't Mean
It doesn't mean the fatigue is imaginary or unimportant. Sleep apnea, insomnia, depression, medication side effects, B12 deficiency, and other common causes aren't on the current panel. Persistent or worsening fatigue especially with weight loss, shortness of breath, chest pain, fainting, fever, or neurological symptoms should be evaluated by a healthcare professional promptly.
What Rythm adds is something genuinely hard to get elsewhere: the same broad panel, repeated under similar conditions, so you can tell a temporary blip from your real baseline and if need be hand your doctor a pattern instead of a guess.