Hair Loss: Why It Happens, What to Test, and What Actually Works
Hair loss has become a large market for supplements, shampoos, serums, red-light devices, injections, compounded products and increasingly expensive promises. The clinical problem is that hair loss is not one condition. A widening part in a woman after menopause, diffuse shedding three months after rapid weight loss, progressive temple recession in a man, and a painful scalp with areas of scarring may all be described by the patient as “my hair is falling out,” yet they are not treated the same way.
Before choosing a medication, supplement, procedure or device, we need to know what process is affecting the follicle.
One-Minute Read
Hair loss can be temporary or progressive, diffuse or patterned, inflammatory or non-inflammatory. Male and female pattern hair loss gradually miniaturize susceptible follicles. Telogen effluvium produces more diffuse shedding and often appears several months after illness, surgery, childbirth, severe stress, rapid weight loss, inadequate calorie or protein intake, or a medication change. Alopecia areata, traction alopecia, infection and inflammatory scarring disorders require different evaluation and treatment.
Laboratory testing should follow the history rather than replace it. CBC, ferritin and iron studies, thyroid testing and selected nutrient testing may be useful. Androgen evaluation may be appropriate when women also have acne, hirsutism, irregular cycles or other signs of androgen excess. Heavy-metal testing belongs in the conversation when there is a credible exposure, not as routine hair-loss screening.
Minoxidil remains one of the better-supported treatments for pattern hair loss. Finasteride, dutasteride, spironolactone, PRP, microneedling, photobiomodulation and other options can have roles in selected patients. Supplements are most defensible when they correct an actual deficiency. The treatment should follow the diagnosis.
Not sure what pattern you are seeing?
The HormoneSynergy® Hair Loss Assessment asks about the timing and pattern of hair loss, recent illness and weight change, nutrition, medications, hormones, thyroid history, scalp symptoms, family history and other clues that can help organize a clinical evaluation.
Hair Loss Is a Symptom, Not a Diagnosis
Normal hair follicles move through growth, transition, rest and shedding phases. Hair is shed every day. The concern is a sustained departure from someone’s usual pattern: a widening part, reduced density, recession, obvious patches, much heavier shedding, scalp inflammation or progressive loss that continues month after month.
Androgenetic alopecia, usually called male or female pattern hair loss, involves gradual miniaturization of genetically susceptible follicles. Women frequently notice widening through the central part or reduced crown density. Men more often notice changes at the temples, frontal hairline and crown. Dihydrotestosterone, or DHT, participates in this process, but circulating androgen levels do not tell the whole story. Follicular sensitivity is important, and women can develop female-pattern hair loss even when blood androgen measurements are within the laboratory reference range.
Our discussion of DHT and androgenetic alopecia looks more closely at why androgen signaling affects some follicles and not others. Women may also find our clinical review of female hair loss and hormones useful.
Telogen effluvium is different. A physiologic stressor shifts an unusually large number of follicles into the resting phase. The shedding usually does not begin immediately. It may appear two or three months after the event, which is why patients sometimes fail to connect the hair loss with an illness, operation, childbirth, stressful period, medication change or rapid reduction in weight.
Alopecia areata is an autoimmune form of non-scarring hair loss that often causes smooth patches. Traction alopecia results from repeated tension on the follicle. Inflammatory scarring alopecias can permanently destroy follicles and deserve early dermatology evaluation.
The Timeline Often Gives Us the First Useful Clue
When someone tells us that hair shedding suddenly increased, one of the first questions is what happened during the preceding several months. Fever, significant infection, surgery, hospitalization, childbirth, substantial emotional or physical stress, rapid weight loss and medication changes can all precede diffuse shedding.
The delay is biologically plausible because the follicle does not simply fall out at the moment of the insult. The event changes the hair cycle, and the increased shedding becomes visible later.
This is also why changing shampoos after the shedding has begun frequently does little. The relevant event may already be months in the past.
What Should Be Tested?
Not every patient with thinning hair needs a large laboratory panel. Testing should be selected from the history, examination, diet, medications and pattern of hair loss.
A CBC, ferritin and iron studies, and thyroid evaluation are common considerations when the history supports them. Vitamin B12, folate, zinc and vitamin D may be useful when diet, symptoms, medications or medical history suggest increased risk of deficiency. Women with acne, increased facial or body hair, irregular cycles or other evidence of androgen excess may need a more specific androgen evaluation.
Iron deserves particular care because low iron stores can contribute to shedding, but taking iron without establishing a need is not good medicine. Our Iron Supplements: When You Need Them, When You Don’t, and Why Testing Comes First Mini Stack explains how ferritin, hemoglobin and iron studies fit into the decision.
Thyroid disease belongs in the differential because both hypothyroidism and hyperthyroidism can produce diffuse hair loss. Correcting the thyroid disorder may allow recovery, although hair cycling responds slowly. Our thyroid health and autoimmune disease guide provides more background on thyroid evaluation.
Heavy Metals Should Be Tested When the Exposure History Supports It
Lead, mercury, arsenic and thallium can cause systemic illness, and some significant exposures can produce hair shedding. They are not routine explanations for ordinary pattern hair loss or uncomplicated telogen effluvium.
Testing becomes more reasonable when there is a credible source: occupational or industrial exposure, contaminated food or water, a spill, an imported remedy or supplement, or another specific environmental concern. The appropriate specimen also depends on the metal and timing of exposure. Blood is generally used for lead. Mercury evaluation varies with the form of exposure. Recent arsenic exposure is usually assessed with urine, preferably with speciation. Thallium exposure is commonly evaluated with urine.
Hair analysis has important limitations because external contamination can alter the result and reference ranges are poorly standardized for many metals. A positive hair measurement does not automatically establish clinical toxicity.
Menopause Can Change Hair Without Being the Only Explanation
Hair changes are common during perimenopause and after menopause. Declining estrogen can alter hair diameter and the growth cycle, while the relative influence of androgen signaling may become more apparent in genetically susceptible follicles. Some women notice a wider part, reduced crown density or a smaller ponytail rather than dramatic shedding.
That does not mean that every midlife woman with thinning hair needs hormone therapy. Thyroid function, iron status, nutrition, recent illness, medications, stress, weight change and inherited pattern hair loss still need consideration. Hormones belong in the evaluation without becoming the explanation for everything.
For the broader physiologic context, see Menopause: What Actually Happens to Your Body.
Rapid Weight Loss, GLP-1 Treatment and Hair Shedding
Hair shedding during substantial weight loss deserves a careful nutritional and medical review. Rapid weight reduction itself is a recognized physiologic trigger for telogen effluvium. The risk becomes more plausible when calorie intake falls sharply, appetite is poor, protein intake becomes inadequate, or iron, zinc and other nutrients are no longer being consumed in sufficient amounts.
This can occur with severe dieting, bariatric surgery, illness and during anti-obesity treatment when weight loss is rapid or food intake falls substantially. It should not automatically be interpreted as proof that a GLP-1 medication is directly toxic to the hair follicle.
When appetite suppression is strong, the remaining food has to cover nutritional needs more efficiently. Protein deserves particular attention because inadequate energy and protein intake are both recognized contributors to diffuse shedding. Our guide to nutrition during GLP-1 treatment addresses protein, nutrient intake, hydration and the problem of eating too little. For a broader discussion of protein requirements with aging and weight loss, see Protein After 50: How Much Do You Need to Preserve Muscle?
What Actually Works for Pattern Hair Loss?
Topical minoxidil remains a foundational treatment for androgenetic alopecia and is FDA-approved for pattern hair loss. Five-percent formulations are commonly used. Scalp irritation, unwanted facial hair and temporary early shedding can occur, and the benefit generally diminishes after treatment is stopped.
Low-dose oral minoxidil has moved into common specialist practice, although it remains an off-label treatment for hair loss. A 2024 randomized trial in men comparing 5 mg oral minoxidil with 5% topical minoxidil found that oral therapy was not superior overall at 24 weeks, although photographic improvement at the vertex favored oral therapy. Oral treatment also introduces systemic considerations that topical treatment does not. Blood pressure, heart rate, cardiovascular history, kidney history, edema, medications and pregnancy status may influence whether it is reasonable for a particular patient.
Oral minoxidil is still minoxidil. The FDA labeling for its original antihypertensive indication carries a boxed warning that includes pericardial effusion and possible tamponade. Doses used for hair loss are much lower than traditional antihypertensive doses, but low dose does not mean zero risk.
Finasteride reduces conversion of testosterone to DHT by inhibiting type II 5-alpha-reductase. Oral finasteride 1 mg is FDA-approved for male pattern hair loss. Dutasteride inhibits both type I and type II 5-alpha-reductase and is used off-label for hair loss in the United States. Spironolactone is also used off-label in selected women, particularly when androgen sensitivity or hyperandrogenism is part of the clinical picture.
Compounded topical finasteride is sometimes promoted as a way to avoid systemic exposure. Absorption still occurs. The FDA issued a 2025 warning regarding adverse-event reports with compounded topical finasteride and specifically emphasized potential systemic effects and transfer risk to someone who is pregnant or could become pregnant.
Alopecia Areata Is a Different Disease
Finasteride, dutasteride and spironolactone target androgen pathways. They do not treat the autoimmune mechanism responsible for alopecia areata.
Limited patchy alopecia areata is often treated by dermatologists with intralesional corticosteroid injections or topical corticosteroids. Severe disease now has FDA-approved systemic JAK-pathway treatments, including baricitinib, ritlecitinib and deuruxolitinib for their respective approved patient populations.
These medications can produce substantial regrowth in some patients, but they require appropriate patient selection and monitoring. Their labeling includes serious warnings involving infection and other systemic risks.
PRP, Microneedling and Red-Light Therapy Can Have a Role
Platelet-rich plasma, or PRP, has randomized-trial and meta-analysis data suggesting improvements in hair density or thickness in some patients with androgenetic alopecia. One limitation is the lack of standardization among PRP protocols. Preparation methods, platelet concentrations, injection techniques and schedules vary considerably.
Microneedling is generally used as an adjunct rather than a stand-alone replacement for medical therapy. Recent randomized-trial meta-analysis has found improved hair count and diameter when microneedling is added to topical minoxidil compared with minoxidil alone.
Photobiomodulation and low-level light devices can also produce modest improvements in hair density in some patients with androgenetic alopecia. As with PRP and microneedling, the device should complement a diagnosis rather than become a substitute for one.
Supplements: Correct Deficiencies Rather Than Treating Hair Loss Blindly
Iron deficiency, inadequate protein intake, zinc deficiency and other nutritional problems can contribute to shedding. Correcting an identified deficiency is medically different from taking a high-dose nutrient because the bottle has hair on the label.
Iron should not be taken indefinitely without knowing whether it is needed. Excess zinc can contribute to copper deficiency. Too much selenium or vitamin A can also produce problems. High-dose biotin has not been shown to reverse ordinary androgenetic alopecia and can interfere with some thyroid, hormone and cardiac laboratory assays.
Collagen, omega-3s and various “hair vitamins” may contribute to overall nutrition, but they should not be presented as replacements for minoxidil, treatment of androgen-sensitive hair loss, appropriate management of alopecia areata, correction of thyroid disease, or treatment of an actual nutritional deficiency.
For the broader supplement framework, see What Vitamins Should I Take? and Supplements in Longevity Medicine: How to Tell What Helps, What’s Hype, and What to Stop.
Medicine, Not Marketing.
The presence of biotin, collagen, saw palmetto, peptides, “growth factors,” exosomes or a long ingredient list does not establish that a treatment can reverse the condition causing someone’s hair loss. Newer therapies may eventually prove useful, but novelty should not displace a diagnosis or a better-studied treatment simply because the product is described as regenerative, natural, personalized or cutting-edge.
When Hair Loss Needs Dermatology Promptly
Scalp pain or burning, pustules, marked redness or scale, rapidly enlarging patches, eyebrow or eyelash loss, extensive body-hair loss, or areas of scalp that appear smooth and shiny deserve closer evaluation. Sudden shedding accompanied by systemic illness, unexplained anemia, significant endocrine symptoms or suspected medication toxicity also deserves medical attention.
Scarring alopecia deserves particular respect because once follicles are destroyed, a hair-growth stimulant cannot restore them. Dermatologists may use dermoscopy or trichoscopy to evaluate miniaturization, broken hairs, inflammation and follicular openings. A scalp biopsy is sometimes necessary when the diagnosis remains uncertain or scarring disease is suspected.
Start With the Pattern
The useful question is not simply, “What can I take for hair loss?” We want to know whether the follicle is miniaturizing, whether too many hairs have shifted into a shedding phase, whether inflammation is damaging the scalp, whether nutrition has become inadequate, whether thyroid or hormonal physiology is contributing, and whether more than one process is occurring at the same time.
Once the diagnosis is clearer, treatment becomes much more rational. Pattern hair loss may call for minoxidil and, in selected patients, treatment directed at androgen signaling. Telogen effluvium requires attention to the trigger and recovery of adequate nutrition. Alopecia areata requires treatment directed at an autoimmune disease. Scarring alopecia needs dermatologic treatment aimed at preventing additional permanent follicle loss.
Hair thinning or shedding and not sure where to begin?
The HormoneSynergy® Hair Loss Assessment can help you organize the pattern, timing and possible contributors before deciding which questions deserve further evaluation.
Selected References
Penha MA, Miot HA, Kasprzak M, Müller Ramos P. Oral Minoxidil vs Topical Minoxidil for Male Androgenetic Alopecia: A Randomized Clinical Trial. JAMA Dermatology. 2024;160(6):600-605.
Vañó-Galván S, Pirmez R, Hermosa-Gelbard A, et al. Safety of low-dose oral minoxidil for hair loss: a multicenter study of 1404 patients. Journal of the American Academy of Dermatology. 2021;84(6):1644-1651.
Akiska YM, Mirmirani P, Roseborough I, et al. Low-Dose Oral Minoxidil Initiation for Patients With Hair Loss: An International Modified Delphi Consensus Statement. JAMA Dermatology. 2025;161(1):87-95.
Gupta AK, Talukder M, Williams G, et al. Low-dose oral minoxidil and topical minoxidil: consensus recommendations for managing male and female pattern hair loss using a modified Delphi process. Expert Opinion on Pharmacotherapy. 2026;27(3):253-261.
Frazier WT, et al. Hair Loss: Diagnosis and Treatment. American Family Physician. 2024;110(3).
Ahmed KMA, et al. Evaluating the efficacy and safety of combined microneedling therapy versus topical minoxidil in androgenetic alopecia: a systematic review and meta-analysis. Archives of Dermatological Research. 2025.
U.S. Food and Drug Administration. FDA alerts health care providers, compounders and consumers of potential risks associated with compounded topical finasteride products. April 22, 2025.
Frequently Asked Questions
What blood tests are commonly considered for hair loss?
Testing should be individualized. CBC, ferritin and iron studies, and thyroid testing are common considerations. Vitamin B12, folate, zinc or vitamin D may be reasonable when the history suggests increased risk. Women with clinical signs of androgen excess may require additional androgen testing.
Can menopause cause hair loss?
Menopause can contribute to changes in hair diameter, growth cycling and female-pattern thinning. Estrogen decline and relative androgen effects may contribute, but menopause should not automatically be assumed to be the only cause. Thyroid disease, iron status, nutrition, medications, genetics and other conditions still need consideration.
Can GLP-1 treatment cause hair shedding?
Hair shedding can occur during periods of substantial weight loss. Rapid weight reduction, low calorie intake, inadequate protein and nutrient insufficiency are recognized triggers for telogen effluvium. Hair shedding during GLP-1 treatment should therefore prompt a review of the pace of weight loss, food intake, protein, nutrient status and other possible causes rather than automatically being attributed to direct medication toxicity.
Does biotin help common hair loss?
True biotin deficiency can affect hair and nails, but routine high-dose biotin has not been shown to reverse common androgenetic alopecia. High doses can also interfere with certain laboratory tests, including some thyroid, hormone and cardiac assays.
Is oral minoxidil FDA-approved for hair loss?
No. Low-dose oral minoxidil is increasingly used by hair-loss specialists, but it remains off-label for hair loss. Treatment should be individualized because systemic side effects and cardiovascular considerations differ from topical therapy.
Educational use only. HormoneSynergy® educational content is not a diagnosis or individualized treatment plan. Prescription medications, off-label treatments and procedures should be selected and monitored by an appropriately licensed clinician. Patchy, inflammatory, rapidly progressive or potentially scarring hair loss should be evaluated by a qualified medical professional.
This article is part of the HormoneSynergy® Longevity Medicine education series covering preventive cardiology, metabolic health, hormone optimization, body composition, and advanced diagnostics for healthy aging.
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