This article explains exactly how long melatonin takes to work by formulation type, why most people take it wrong, and how to time it correctly for your specific use case. See also: What Is Sleep Onset Latency and How to Reduce It and the Melatonin Dosage Calculator.

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The Direct Answer

How long does it take melatonin to kick in? Immediate-release melatonin reaches peak plasma concentration in approximately 36 minutes (Tmax ~0.6 hours) — but onset varies significantly by formulation:

Formulation	Onset Time	Peak Concentration	Best For
Sublingual spray/strip	15–20 minutes	20–30 minutes	Fastest onset; acute sleep initiation
Immediate-release tablet	30–45 minutes	36–60 minutes	Standard use; most studied
Gummies	45–90 minutes	60–90 minutes	Slowest; gelatin matrix delays absorption
Extended-release tablet	60+ minutes (gradual)	Sustained over 6–8 hours	Sleep maintenance; night waking

But onset speed is the wrong question. Melatonin is not a sedative. It is a circadian signal — a chemical message to the brain that darkness has arrived and sleep should begin. Whether melatonin works depends not on how fast it enters your bloodstream, but on when it arrives relative to your body's internal clock.

The three rules that determine whether melatonin works:

1. Take it 1–2 hours before your target sleep time — not 10 minutes before bed
2. Take 0.5–1 mg, not 5–10 mg — the physiological dose range achieves the same receptor activation as high doses; higher doses cause next-day grogginess without sleep benefit
3. Reduce light exposure after taking it — melatonin production is suppressed by light regardless of whether you supplement; screens after taking melatonin actively undermine its signal

Use the Melatonin Dosage Calculator for personalised timing and dosing based on your sleep schedule and use case.

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You take a melatonin gummy at 11:15 p.m. You lie down at 11:30 p.m. You are still awake at 12:30 a.m., wondering why the melatonin "isn't working."

This is the most common melatonin failure mode — and it is almost never a melatonin problem. It is a timing problem.

Melatonin does not work like a sleeping pill. It does not activate GABA receptors to produce sedation. It does not slow brain activity or cause physiological drowsiness through any sedative mechanism. What it does is signal the suprachiasmatic nucleus (SCN) — the brain's master circadian clock — that darkness has arrived and biological night has begun. This signal adjusts the timing of your internal clock, gradually shifting the onset of sleepiness forward (or backward) over one to several nights.

When you take melatonin 10 minutes before bed, the peak plasma concentration arrives at approximately midnight — an hour after your target sleep time. The signal is late. The window has passed. Your circadian system has already moved on to its next phase. The gummy "didn't work" not because melatonin doesn't work, but because you gave a circadian signal after the circadian window had closed.

This article explains the complete pharmacology, the correct timing by use case, the dose-response science (why your 10 mg tablet is almost certainly making things worse, not better), and the conditions under which melatonin genuinely helps — and those under which it does not.

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How Long Does It Take Melatonin to Kick In: The Complete Guide

The Biology: What Melatonin Actually Does

Melatonin as a Circadian Signal, Not a Sedative

Melatonin is a hormone synthesised and secreted by the pineal gland in response to darkness. Its production is driven by the SCN, which receives light input from the retina via the retinohypothalamic tract. When light falls — particularly short-wavelength blue light — melatonin synthesis is suppressed. When darkness arrives, melatonin production begins, typically 1–3 hours before habitual sleep onset.

The resulting dim-light melatonin onset (DLMO) — the point at which melatonin concentrations exceed 3–10 pg/mL in plasma — is the most reliable marker of circadian phase available without laboratory testing. DLMO typically occurs 2–3 hours before habitual sleep time in healthy adults. It is not the cause of sleepiness per se — it is the signal that primes the sleep-initiation cascade.

Melatonin acts on two primary receptor subtypes:

• MT1 receptors — mediate the acute sleepiness-promoting and body-temperature-reducing effects; high affinity
• MT2 receptors — mediate the phase-shifting (circadian clock-resetting) effects; drive the chronobiotic action

Exogenous melatonin works through both pathways. The MT1 effect produces the mild sedation that people experience 30–45 minutes after taking it. The MT2 effect shifts the circadian clock — the mechanism responsible for jet lag recovery, shift work adaptation, and delayed sleep phase correction. The MT1 sedation is real but modest. The MT2 phase shift is where melatonin's primary clinical value lies.

This distinction is why timing matters more than speed of onset: you are not trying to get melatonin into your bloodstream quickly. You are trying to deliver the circadian signal at the right phase of your internal clock — which requires taking it 1–2 hours before target sleep time, not immediately before.

The DLMO Window: Why Timing Is Everything

The phase response curve (PRC) for melatonin defines when a dose will advance, delay, or have no effect on the circadian clock. A dose taken in the early evening (before DLMO) will advance the clock — moving sleep onset earlier. A dose taken after DLMO (late evening) will have minimal phase-shifting effect. A dose taken in the early morning will delay the clock — making sleep onset later.

For most adults using melatonin to fall asleep earlier or on time:

• The optimal administration window is 1–2 hours before target sleep time
• The 2025 CNS Spectrums review "Melatonin dose and timing: Do we have it right?" (doi:10.1017/S109285292510062X) recommended that "the best time to administer melatonin is around 6 PM (1–2 hours before bedtime)" — noting this should be the standard of care
• Taking melatonin at bedtime — when most people take it — delivers the signal at or after DLMO, in a window where the phase-shifting effect is minimal

This explains why people who take melatonin "right before bed" frequently find it ineffective: they have missed the PRC window that produces the circadian advance they need.

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Onset Time by Formulation: The Complete Comparison

Immediate-Release Tablets and Capsules

Immediate-release melatonin is the most studied formulation and the pharmacokinetic reference standard. A 2024 randomised crossover study (Journal of Dietary Supplements) comparing extended-release and immediate-release pharmacokinetics confirmed that immediate-release melatonin reaches peak plasma concentrations (Tmax) at approximately 0.6 hours (36 minutes) after oral ingestion, regardless of fed/fasted state.

Key pharmacokinetics for immediate-release:

• Onset: 30–45 minutes
• Peak (Tmax): ~36 minutes
• Half-life: 1–2 hours
• Duration of action: 4–5 hours total
• Absorption: Relatively complete; not significantly affected by food

Best use case: Standard sleep onset support when taken 1–2 hours before target sleep time. The most evidence-based choice for most people.

Sublingual Sprays and Strips

Sublingual delivery bypasses first-pass hepatic metabolism by absorbing directly through the sublingual mucosa into systemic circulation. This produces a substantially faster onset:

• Onset: 15–20 minutes
• Peak: 20–30 minutes
• Advantage: Fastest onset; useful when sleep onset is urgently needed
• Limitation: Shorter duration; may not maintain blood levels through a full sleep cycle

Best use case: Night awakenings (waking at 2–3 a.m. and needing to return to sleep quickly); travel when sleep windows are unpredictable; situations where 30-minute advance planning is not possible.

Gummies

Gummies are the most popular consumer melatonin format — and the worst pharmacokinetic performer. The gelatin, sugar, and binding matrix that gives gummies their texture must be fully digested before melatonin is absorbed. This significantly delays onset:

• Onset: 45–90 minutes
• Peak: 60–90 minutes
• Variability: High — dependent on stomach contents, individual digestion rate, and gummy composition

There is an additional problem with gummies beyond delayed onset: dose inaccuracy. Consumer gummy melatonin is notoriously poorly standardised. A 2023 Journal of the American Medical Association study found that melatonin gummies varied from 74% to 347% of the labelled dose — meaning a "5 mg" gummy might contain anywhere from 3.7 mg to 17.4 mg. For a hormone with a meaningful dose-response curve and a narrow therapeutic window (see dose section below), this degree of variability is clinically significant.

Best use case: Not recommended as a primary melatonin formulation given delayed onset and dose inaccuracy. If used, take 60–90 minutes before target sleep time to account for slow absorption.

Extended-Release (Prolonged-Release) Tablets

Extended-release melatonin is designed to dissolve slowly, maintaining plasma levels over 6–8 hours rather than the 4–5 hours of immediate-release formulations. The 2024 Journal of Dietary Supplements pharmacokinetics RCT confirmed that extended-release maintains plasma levels through the night more consistently than immediate-release, while immediate-release achieves a higher and faster initial peak.

• Onset: 60+ minutes (gradual build, no sharp peak)
• Duration: 6–8 hours of maintained plasma levels
• Advantage: Reduces night waking and sleep fragmentation; supports sleep maintenance through the full night
• Limitation: Slower to initiate sleep onset; not ideal as a pure sleep-onset aid

Best use case: Adults who fall asleep adequately but wake frequently in the second half of the night; older adults (who have shorter half-lives for exogenous melatonin due to altered pharmacokinetics); shift workers who need sustained melatonin levels during a non-biological sleep period.

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The Dose Problem: Why More Is Not Better

This is the most important section for anyone currently taking 5 mg, 10 mg, or higher doses of melatonin — which is most of the U.S. market.

The Physiological Dose Range

Endogenous melatonin peaks at approximately 80–150 pg/mL in healthy young adults during the biological night. Supplemental doses as low as 0.1–0.3 mg can achieve plasma concentrations within or above this physiological range. A 1 mg dose produces plasma levels approximately 10–100× higher than the natural nocturnal peak.

A 10 mg dose produces plasma levels 100–1,000× higher than the physiological range.

The receptor response does not scale proportionally with these concentrations. MT1 and MT2 receptors saturate at physiological doses. Flooding them with supraphysiological concentrations does not produce better sleep — it produces:

1. Extended receptor occupancy — melatonin remains active for hours longer than endogenous melatonin, potentially disrupting the morning cortisol awakening response and producing daytime grogginess
2. Receptor downregulation over time — chronic supraphysiological dosing may reduce receptor sensitivity, requiring progressively higher doses for the same effect
3. Circadian signal disruption — high-dose melatonin taken at night can produce a larger phase shift than intended, advancing sleep timing more than desired and causing early morning awakening

The research supports this clearly. A 2024 systematic review of 26 trials confirmed that doses above 5 mg show no added benefit for sleep onset and increase next-day grogginess. The dose-response curve for melatonin is flat above approximately 0.3 mg for sleep onset latency reduction. The 2025 CNS Spectrums review noted that optimal doses are in the 0.5–3 mg range.

The practical guidance from the evidence:

Starting dose protocol:
  Night 1-7:    0.5 mg, taken 1 hour before target sleep time
  If no effect: Increase to 1 mg
  If still no effect: Increase to 2–3 mg
  Maximum effective dose for most adults: 3–5 mg
  10 mg doses: Not supported by evidence; likely counterproductive

Use the Melatonin Dosage Calculator to identify the optimal starting dose and timing for your specific sleep pattern, chronotype, and use case.

The Dose-Population Interaction

Not all adults metabolise melatonin identically. Two clinically relevant differences:

Older adults: Melatonin clearance slows with age — older adults clear melatonin 40–60% more slowly than younger adults. A 0.5 mg dose in a 65-year-old may produce a similar or higher exposure than a 2 mg dose in a 25-year-old. The evidence-based starting dose for adults over 65 is 0.5 mg immediate-release, not the 5–10 mg doses commonly sold in retail pharmacies.

People on oral contraceptives or certain medications: Oral contraceptives inhibit CYP1A2 — the primary hepatic enzyme responsible for melatonin metabolism — and raise melatonin blood levels 2–3× above normal for a given dose. Other CYP1A2 inhibitors include fluoroquinolone antibiotics and fluvoxamine. People taking these medications may need lower doses than recommended or should discuss melatonin use with their prescriber.

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When Melatonin Works — and When It Doesn't

Melatonin has high evidence of benefit for some conditions and essentially no benefit for others. Understanding this distinction prevents misuse and helps identify when sleep problems require a different intervention.

High Evidence: Melatonin Works Well

Jet lag — the most evidence-robust application. Melatonin taken at the destination bedtime for 2–5 nights after transatlantic or transpacific travel significantly reduces jet lag symptoms by advancing the circadian clock to align with the destination time zone. The Jet Lag Recovery Calculator provides destination-specific timing recommendations.

Delayed sleep phase syndrome (DSPS) — people whose natural DLMO is significantly later than conventional sleep times respond well to low-dose melatonin taken 2–6 hours before the current (late) DLMO, progressively advancing the clock. This is the condition melatonin was originally studied for.

Shift work — melatonin taken at the start of daytime sleep windows (for night shift workers) modestly improves total daytime sleep time and helps consolidate sleep against the circadian drive for wakefulness.

Short-term sleep onset latency reduction — the Ferracioli-Oda et al. meta-analysis (often cited) found an average reduction in sleep onset latency of ~7 minutes. Modest, but real, and meaningful for people with mild sleep onset delays.

Low or No Evidence: When Melatonin Won't Help

Chronic insomnia driven by hyperarousal — when the primary mechanism of insomnia is HPA axis activation, racing thoughts, and conditioned arousal (the bedroom-wakefulness association), melatonin does not address the underlying mechanism. CBT-I is the evidence-based treatment for this condition. Use the Insomnia Self-Assessment to identify whether hyperarousal insomnia is present.

Sleep debt — melatonin does not repay sleep debt. It signals sleep timing — it does not increase the depth, duration, or quality of sleep in people with accumulated sleep deprivation. The Sleep Debt Calculator quantifies your actual deficit; the Sleep Recovery Planner builds the payback schedule that actually addresses it.

Sleep maintenance insomnia (waking in the second half of the night) — immediate-release melatonin is largely cleared from the system by 3–4 a.m. and does not prevent second-half awakenings. Extended-release melatonin has more evidence for this application, but sleep maintenance insomnia often has structural causes (OSA, cortisol dysregulation, circadian issues) that require specific investigation.

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Why Melatonin "Isn't Working" — The Seven Most Common Timing and Dosing Errors

Error	What Happens	Fix
Taking it 5–10 minutes before bed	Peak arrives after you're already frustrated in bed trying to sleep	Take 60–90 minutes before target sleep time
Taking 10 mg "for stronger effect"	Receptor saturation; extended next-day grogginess; no additional sleep benefit	Reduce to 0.5–1 mg; titrate up from there
Taking it every night as a sedative	It is not a sedative; chronic nightly use for non-circadian insomnia does not treat the underlying condition	Use for circadian issues; address insomnia with CBT-I
Using gummies and wondering why they're slow	Gelatin matrix delays absorption 45–90 minutes vs. 30 minutes for tablets	Switch to immediate-release tablet or sublingual
Continuing to use screens after taking it	Light suppresses endogenous melatonin and undermines the signal melatonin is trying to send	Dim lights and reduce screens immediately after taking
Taking it at the wrong circadian phase	Melatonin taken after DLMO has minimal phase-advancing effect	Take 1–2 hours before target sleep time, not at bedtime
Expecting it to fix sleep debt	Melatonin is a timing tool, not a recovery tool	Measure and address sleep debt at sleepdebtcalc.com

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The Melatonin Timing Self-Assessment

Identify your use case to determine correct timing:

• I want to fall asleep earlier than my body currently allows (delayed sleep phase)
• I am travelling across time zones (jet lag)
• I work night shifts and need to sleep during the day
• I occasionally struggle to fall asleep but my schedule is regular
• I fall asleep fine but wake in the middle of the night
• I have chronic insomnia — difficulty falling or staying asleep most nights for months

Scoring:

• Items 1–2: Classic melatonin use case — take 0.5–1 mg, 1–2 hours before target sleep time; use the Melatonin Dosage Calculator for jet lag-specific timing
• Item 3: Shift work — melatonin 0.5–3 mg at the start of your planned daytime sleep window; timing requires individual adjustment
• Item 4: Occasional use — immediate-release 0.5–1 mg, 45–60 minutes before bed is reasonable; check sleep debt first at sleepdebtcalc.com
• Item 5: Extended-release 0.5–2 mg may help; also screen for OSA with the Sleep Apnea Risk Screener and investigate cortisol-related night waking
• Item 6: Melatonin is unlikely to be sufficient — use the Insomnia Self-Assessment and consider CBT-I referral

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Frequently Asked Questions

How long does it take melatonin to kick in?

Immediate-release melatonin typically begins working within 20–40 minutes and reaches peak plasma concentration at approximately 36 minutes. However, onset time varies by formulation: sublingual sprays begin working in 15–20 minutes; standard tablets in 30–45 minutes; gummies in 45–90 minutes due to their gelatin matrix slowing absorption. Extended-release tablets have a gradual onset over 60+ minutes but sustain levels for 6–8 hours. Critically, onset time is not the primary variable that determines whether melatonin helps — timing relative to your body's internal clock is far more important.

When should I take melatonin before bed?

The evidence-based recommendation is 1–2 hours before your target sleep time — not 10–30 minutes before. Because melatonin is a circadian signal rather than a sedative, it needs to arrive before your body's dim-light melatonin onset (DLMO) window to produce its phase-advancing effect. The 2025 CNS Spectrums clinical review specifically recommended melatonin administration approximately 2 hours before desired bedtime as the standard of care. Taking it immediately before bed delivers the signal after the circadian window has largely closed, which is why many people find it ineffective.

Does more melatonin help you fall asleep faster?

No — and high doses are likely counterproductive. Physiological nocturnal melatonin peaks at 80–150 pg/mL, achievable with doses as low as 0.1–0.3 mg. MT1 and MT2 receptors saturate at physiological doses; flooding them with 5–10 mg produces 100–1,000× physiological concentrations with no additional sleep benefit and meaningful downsides: extended receptor occupancy causing next-day grogginess, and potential circadian disruption from excessive phase shifts. A 2024 systematic review of 26 trials confirmed that doses above 5 mg show no added sleep benefit. Start at 0.5 mg and titrate slowly.

How long does melatonin last once it kicks in?

Immediate-release melatonin has an elimination half-life of 1–2 hours, producing a total action window of approximately 4–5 hours after the peak. For a tablet taken at 9 p.m. peaking at 9:36 p.m., meaningful plasma levels persist until approximately 1–2 a.m. Extended-release melatonin maintains plasma levels over 6–8 hours, making it preferable for sleep maintenance issues. If you are waking at 3–4 a.m. after a 10 p.m. dose of immediate-release melatonin, the wake is occurring after melatonin has been largely cleared — this is not a melatonin dosing problem but a separate sleep maintenance issue.

Why isn't melatonin working for me?

The most common reasons are: taking it too close to bedtime (peak arrives after sleep window closes), taking too high a dose (counterproductive above 3–5 mg), using gummies with variable absorption timing, continuing screen use after taking it (light suppresses the melatonin signal you are trying to supplement), or expecting it to treat insomnia that is not circadian in origin. Chronic insomnia driven by hyperarousal, conditioned arousal, or sleep debt does not respond to melatonin because melatonin does not address those mechanisms. Use the Insomnia Self-Assessment to determine whether your sleep problem is circadian or not.

What is the right melatonin dose for adults?

The evidence-based starting dose for healthy adults is 0.5–1 mg immediate-release taken 1–2 hours before target sleep time. Most adults respond adequately within this range. If no effect is apparent after one week, increase to 2–3 mg. The evidence does not support doses above 5 mg for sleep purposes — the 2024 systematic review of 26 trials found no additional benefit above this threshold and increased grogginess risk. Older adults (65+) should start at 0.5 mg due to slower CYP1A2-mediated clearance producing higher plasma exposures for a given dose.

Is melatonin safe to take every night?

Short-term melatonin use (up to 3 months) is generally considered safe for most healthy adults based on available evidence. Long-term nightly use is less well-studied. There is theoretical concern that chronic supraphysiological dosing may reduce endogenous melatonin production and receptor sensitivity over time, though this has not been definitively established in human RCTs. For ongoing sleep difficulties, the more appropriate long-term intervention is addressing the root cause — whether sleep debt, circadian disruption, insomnia pattern, or sleep disorder — rather than indefinite supplementation. The Melatonin Dosage Calculator can help you use it appropriately for your specific situation.

Can melatonin help with jet lag?

Yes — jet lag is the application for which melatonin has the strongest and most consistent evidence. Taking 0.5–3 mg at the destination bedtime for 2–5 nights after transatlantic or transpacific travel significantly reduces jet lag symptoms by advancing the circadian clock toward the destination time zone. The timing should align with the destination's evening rather than the departure city's time. The Jet Lag Recovery Calculator provides personalised timing recommendations for your specific flight route and layover schedule.

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The Bottom Line

How long does it take melatonin to kick in is the right question — but it is the less important one. The right questions are: when should you take it relative to your internal clock? And what dose actually works?

The answers the evidence supports:

1. Timing: 1–2 hours before your target sleep time — not immediately before bed
2. Dose: 0.5–1 mg to start; up to 3 mg if needed; nothing above 5 mg is supported by the evidence
3. Formulation: Immediate-release tablet for sleep onset; extended-release for sleep maintenance; sublingual for fastest onset when needed
4. Use case: Melatonin works for circadian problems (jet lag, delayed sleep phase, shift work). It does not fix sleep debt, hyperarousal insomnia, or sleep apnea.
5. After taking it: Turn off screens, dim the lights, and let the signal work — light suppresses the very hormone you just supplemented

Specific actions:

1. Use the Melatonin Dosage Calculator to find your timing and dose
2. Calculate your sleep debt at sleepdebtcalc.com — if sleep debt is the primary problem, melatonin is the wrong tool
3. Use the Insomnia Self-Assessment if you have chronic difficulty sleeping — melatonin is not first-line treatment for clinical insomnia
4. Use the Jet Lag Recovery Calculator for travel-specific timing
5. Check your Chronotype Quiz result — people with a late chronotype may benefit from melatonin more consistently than morning types

Melatonin is a chronobiotic, not a hypnotic. Used correctly — right dose, right time, right formulation, right problem — it is a genuinely useful sleep tool. Used incorrectly — 10 mg swallowed at 11:45 p.m. while checking Instagram — it is a placebo with grogginess side effects.

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Tools Referenced in This Article

• Melatonin Dosage Calculator — Personalised timing and dosing based on your sleep schedule and use case
• Sleep Debt Calculator — Determine whether sleep debt (not circadian timing) is the root cause
• Jet Lag Recovery Calculator — Destination-specific melatonin timing for travel
• Insomnia Self-Assessment — Screen for hyperarousal insomnia that melatonin cannot treat
• Chronotype Quiz — Identify your natural sleep phase and DLMO timing
• Sleep Apnea Risk Screener — Rule out OSA in sleep maintenance cases
• Sleep Recovery Planner — The actual solution to sleep debt that melatonin cannot provide
• Bedtime Calculator — Find your optimal bedtime to pair with melatonin timing

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Related Reading

• What Is Sleep Onset Latency and How to Reduce It — Optimization — Evidence-based strategies for falling asleep faster beyond melatonin
• How to Minimize Jet Lag for Long-Haul Flights — Optimization — Full jet lag protocol including melatonin timing
• How to Reduce Sleep Onset Latency Naturally — Optimization — Non-pharmacological alternatives to melatonin
• Best Bedtime Routine for Sleep Recovery — Optimization — The environmental and behavioural context that makes melatonin work
• Common Myths About Sleep Debt — Optimization — Including the myth that melatonin compensates for insufficient sleep
• How to Use Sleep Restriction Therapy at Home — Optimization — CBT-I approach for chronic insomnia that melatonin cannot treat

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Disclaimer: This article is for educational and informational purposes only and does not constitute medical advice. Melatonin is classified as a dietary supplement in the United States and is not FDA-approved as a drug. If you are pregnant, breastfeeding, taking medications (particularly oral contraceptives, blood thinners, immunosuppressants, or CYP1A2 inhibitors), or have an autoimmune condition, consult a healthcare provider before using melatonin. For children, melatonin should only be used under paediatric supervision. SleepDebtCalc.com tools are designed to support self-awareness and sleep optimisation — they are not diagnostic instruments and should not replace professional medical evaluation.